Series comparison

-[PATCH RESEND 0/3] drm/bridge: it6505: fix DP link traning and improve compatibility
+[PATCH v3 0/5] drm/bridge: it6505: fix DP link traning and improve compatibility
 ...
 Modify training method improve compatibility to these DP devices.
 Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
 ---
-Hermes Wu (3):
+Changes in v3:
 - Patch 1/5 : add commit message for detial about changes
 - Patch 2/5 : fix lost variable struct device *dev;
 - Patch 3/5 : keep changes and remove refactoring
 - Patch 5/5 : merge condition "it6505->step_train_only" check form if condiction into for loop.
 - Link to v2: https://lore.kernel.org/r/20250326-fix-link-training-v2-0-756c8306f500@ite.com.tw
 Changes in v2:
 - 1. Split [PATCH 1/3] into 3 commits
 - 2. Drop non necessary variable auto_ttrain_retry
 - Link to v1: https://lore.kernel.org/all/20250318-fix-link-training-v1-0-19266711142c@ite.com.tw/
 ---
 Hermes Wu (5):
       drm/bridge: it6505: fix link training state HW register reset
       drm/bridge: it6505: check INT_LINK_TRAIN_FAIL while link auto training
       drm/bridge: it6505: modify DP link auto training
       drm/bridge: it6505: modify DP link training work
       drm/bridge: it6505: skip auto training when previous try fail
- drivers/gpu/drm/bridge/ite-it6505.c | 106 ++++++++++++++++++++++--------------
+ drivers/gpu/drm/bridge/ite-it6505.c | 88 +++++++++++++++++++++----------------
-file changed, 66 insertions(+), 40 deletions(-)
+file changed, 50 insertions(+), 38 deletions(-)
 ---
 base-commit: 938fbb16aba8f7b88e0fdcf56f315a5bbad41aad
 change-id: 20250121-fix-link-training-461495494655
 Best regards,
 --
 Hermes Wu <Hermes.wu@ite.com.tw>

-New patch
+[PATCH v3 1/5] drm/bridge: it6505: fix link training state HW register reset
+From: Hermes Wu <Hermes.wu@ite.com.tw>
+When connect to a DP-to-HDMI device which does not connect
+to HDMI sink, it will report DPCD 00200h with SINK_COUNT = "0",
+and issue HPD_IRQ when SINK_COUNT change to "1".
+IT6505 can not recive HPD_IRQ before training done and driver will
+force HW enter training done state when connect to such devices.
+When HW is force to training done state and restart link training,
+bits FORCE_RETRAIN and MANUAL_TRAIN at REG_TRAIN_CTRL1 must be set
+at the same time to reset HW state.
+Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
+---
+ drivers/gpu/drm/bridge/ite-it6505.c | 6 ++++--
+file changed, 4 insertions(+), 2 deletions(-)
+diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
+index XXXXXXX..XXXXXXX 100644
+--- a/drivers/gpu/drm/bridge/ite-it6505.c
++++ b/drivers/gpu/drm/bridge/ite-it6505.c
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
+     mutex_lock(&it6505->aux_lock);
+     it6505_set_bits(it6505, REG_TRAIN_CTRL0,
+             FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
+-    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
++    /* reset link state machine and re start training*/
++    it6505_write(it6505, REG_TRAIN_CTRL1,
++             FORCE_RETRAIN | MANUAL_TRAIN);
+     it6505_write(it6505, REG_TRAIN_CTRL1, AUTO_TRAIN);
+     while (timeout > 0) {
+@@ -XXX,XX +XXX,XX @@ static void it6505_stop_link_train(struct it6505 *it6505)
+ {
+     it6505->link_state = LINK_IDLE;
+     cancel_work_sync(&it6505->link_works);
+-    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
++    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN | MANUAL_TRAIN);
+ }
+ static void it6505_link_train_ok(struct it6505 *it6505)
+--
+.34.1

-[PATCH RESEND 1/3] drm/bridge: it6505: modify DP link auto training
+[PATCH v3 2/5] drm/bridge: it6505: check INT_LINK_TRAIN_FAIL while link auto training
 From: Hermes Wu <Hermes.wu@ite.com.tw>
-IT6505 supports HW link training which will write DPCD and check
+When start link training, interrupt status INT_LINK_TRAIN_FAIL can
-training status automatically.
+use to check link training fail and no need to wait until timeout.
-In the case that driver set link rate at 2.7G and HW fail to training,
+it6505_irq_link_train_fail() remove from interrupt and no longer used.
 it will change link configuration and try 1.65G. And this will cause
 INT_VID_FIFO_ERROR triggered when link clock is changed.
 When video error occurs, video logic is reset and link training restart,
 this will cause endless auto link training.
 Modify link auto training with disable INT_VID_FIFO_ERROR to avoid loop
 and check INT_LINK_TRAIN_FAIL event to abort wait training done.
 Since INT_LINK_TRAIN_FAIL is checked when auto training, it is remove
 from  it6505_int_threaded_handler()
 In order to reset HW link auto training state,
 bits FORCE_RETRAIN and MANUAL_TRAIN at REG_TRAIN_CTRL1 must be set
 at the same time.
 Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
 ---
- drivers/gpu/drm/bridge/ite-it6505.c | 61 +++++++++++++++++++++++++------------
+ drivers/gpu/drm/bridge/ite-it6505.c | 26 +++++++++++++++-----------
-file changed, 42 insertions(+), 19 deletions(-)
+file changed, 15 insertions(+), 11 deletions(-)
 diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
 index XXXXXXX..XXXXXXX 100644
 --- a/drivers/gpu/drm/bridge/ite-it6505.c
 +++ b/drivers/gpu/drm/bridge/ite-it6505.c
 @@ -XXX,XX +XXX,XX @@ static void it6505_int_mask_enable(struct it6505 *it6505)
      it6505_write(it6505, INT_MASK_02, BIT(INT_AUX_CMD_FAIL) |
               BIT(INT_HDCP_KSV_CHECK) | BIT(INT_AUDIO_FIFO_ERROR));
 -    it6505_write(it6505, INT_MASK_03, BIT(INT_LINK_TRAIN_FAIL) |
-+    it6505_write(it6505, INT_MASK_03,
+-             BIT(INT_VID_FIFO_ERROR) | BIT(INT_IO_LATCH_FIFO_OVERFLOW));
-              BIT(INT_VID_FIFO_ERROR) | BIT(INT_IO_LATCH_FIFO_OVERFLOW));
++    it6505_write(it6505, INT_MASK_03, BIT(INT_VID_FIFO_ERROR) |
 +             BIT(INT_IO_LATCH_FIFO_OVERFLOW));
  }
-@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_setup(struct it6505 *it6505)
+ static void it6505_int_mask_disable(struct it6505 *it6505)
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
  static bool it6505_link_start_auto_train(struct it6505 *it6505)
  {
--    int timeout = 500, link_training_state;
+     int timeout = 500, link_training_state;
 +    int link_training_state;
      bool state = false;
++    int int03;
 +    struct device *dev = it6505->dev;
-+    int int03;
-+    unsigned long timeout;
+     mutex_lock(&it6505->aux_lock);
 +
 +    guard(mutex)(&it6505->aux_lock);
 +    /* Disable FIFO error interrupt trigger  */
 +    /* to prevent training fail loop issue   */
 +    it6505_set_bits(it6505, INT_MASK_03, BIT(INT_VID_FIFO_ERROR), 0);
 +
 +    it6505_write(it6505, INT_STATUS_03,
 +             BIT(INT_LINK_TRAIN_FAIL) | BIT(INT_VID_FIFO_ERROR));
 +    int03 = it6505_read(it6505, INT_STATUS_03);
 -    mutex_lock(&it6505->aux_lock);
      it6505_set_bits(it6505, REG_TRAIN_CTRL0,
-             FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
--    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
+     while (timeout > 0) {
 +
 +    /* reset link state machine and re start training*/
 +    it6505_write(it6505, REG_TRAIN_CTRL1,
 +             FORCE_RETRAIN | MANUAL_TRAIN);
      it6505_write(it6505, REG_TRAIN_CTRL1, AUTO_TRAIN);
 -    while (timeout > 0) {
 +    timeout = jiffies + msecs_to_jiffies(100) + 1;
 +    for (;;) {
          usleep_range(1000, 2000);
          link_training_state = it6505_read(it6505, REG_LINK_TRAIN_STS);
 +        int03 = it6505_read(it6505, INT_STATUS_03);
 +        if (int03 & BIT(INT_LINK_TRAIN_FAIL)) {
-+            /* Ignore INT_VID_FIFO_ERROR when auto training fail*/
 +            it6505_write(it6505, INT_STATUS_03,
-+                     BIT(INT_LINK_TRAIN_FAIL) |
++                     BIT(INT_LINK_TRAIN_FAIL));
 +                     BIT(INT_VID_FIFO_ERROR));
 +
-+            if (int03 & BIT(INT_VID_FIFO_ERROR)) {
++            DRM_DEV_DEBUG_DRIVER(dev,
-+                DRM_DEV_DEBUG_DRIVER(dev,
++                         "INT_LINK_TRAIN_FAIL(%x)!",
-+                "video fifo error when training fail (%x)!",
++                          int03);
 +                int03);
 +            }
 +
 +            break;
 +        }
          if (link_training_state > 0 &&
              (link_training_state & LINK_STATE_NORP)) {
-             state = true;
--            goto unlock;
-+            break;
-         }
--        timeout--;
-+        if (time_after(jiffies, timeout))
-+            break;
-     }
--unlock:
--    mutex_unlock(&it6505->aux_lock);
-+    /* recover interrupt trigger*/
-+    it6505_set_bits(it6505, INT_MASK_03,
-+            BIT(INT_VID_FIFO_ERROR), BIT(INT_VID_FIFO_ERROR));
-     return state;
- }
-@@ -XXX,XX +XXX,XX @@ static void it6505_stop_link_train(struct it6505 *it6505)
- {
-     it6505->link_state = LINK_IDLE;
-     cancel_work_sync(&it6505->link_works);
--    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
-+    it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN | MANUAL_TRAIN);
- }
- static void it6505_link_train_ok(struct it6505 *it6505)
 @@ -XXX,XX +XXX,XX @@ static void it6505_irq_audio_fifo_error(struct it6505 *it6505)
          it6505_enable_audio(it6505);
  }
 -static void it6505_irq_link_train_fail(struct it6505 *it6505)
 ...

-New patch
+[PATCH v3 3/5] drm/bridge: it6505: modify DP link auto training
+From: Hermes Wu <Hermes.wu@ite.com.tw>
+IT6505 supports HW link training which will write DPCD and check
+training status automatically.
+In the case that driver set link rate at 2.7G and HW fail to training,
+it will change link configuration and try 1.65G. And this will cause
+INT_VID_FIFO_ERROR triggered when link clock is changed.
+When video error occurs, video logic is reset and link training restart,
+this will cause endless auto link training.
+Modify link auto training with disable INT_VID_FIFO_ERROR to avoid loop
+and check INT_LINK_TRAIN_FAIL event to abort wait training done.
+Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
+---
+ drivers/gpu/drm/bridge/ite-it6505.c | 14 +++++++++++++-
+file changed, 13 insertions(+), 1 deletion(-)
+diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
+index XXXXXXX..XXXXXXX 100644
+--- a/drivers/gpu/drm/bridge/ite-it6505.c
++++ b/drivers/gpu/drm/bridge/ite-it6505.c
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
+     struct device *dev = it6505->dev;
+     mutex_lock(&it6505->aux_lock);
++
++    /* Disable FIFO error interrupt trigger  */
++    /* to prevent training fail loop issue   */
++    it6505_set_bits(it6505, INT_MASK_03, BIT(INT_VID_FIFO_ERROR), 0);
++
++    it6505_write(it6505, INT_STATUS_03,
++             BIT(INT_LINK_TRAIN_FAIL) | BIT(INT_VID_FIFO_ERROR));
+     it6505_set_bits(it6505, REG_TRAIN_CTRL0,
+             FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
+     /* reset link state machine and re start training*/
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
+         link_training_state = it6505_read(it6505, REG_LINK_TRAIN_STS);
+         int03 = it6505_read(it6505, INT_STATUS_03);
+         if (int03 & BIT(INT_LINK_TRAIN_FAIL)) {
++            /* Ignore INT_VID_FIFO_ERROR when auto training fail*/
+             it6505_write(it6505, INT_STATUS_03,
+-                     BIT(INT_LINK_TRAIN_FAIL));
++                     BIT(INT_LINK_TRAIN_FAIL) |
++                     BIT(INT_VID_FIFO_ERROR));
+             DRM_DEV_DEBUG_DRIVER(dev,
+                          "INT_LINK_TRAIN_FAIL(%x)!",
+@@ -XXX,XX +XXX,XX @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
+         timeout--;
+     }
+ unlock:
++    /* recover interrupt trigger*/
++    it6505_set_bits(it6505, INT_MASK_03,
++            BIT(INT_VID_FIFO_ERROR), BIT(INT_VID_FIFO_ERROR));
+     mutex_unlock(&it6505->aux_lock);
+     return state;
+--
+.34.1

-[PATCH RESEND 2/3] drm/bridge: it6505: modify DP link training work
+[PATCH v3 4/5] drm/bridge: it6505: modify DP link training work
 From: Hermes Wu <Hermes.wu@ite.com.tw>
 The DP link training work include auto training and after
-auto training failed "auto_train_retry" times, it switch to
+auto training failed "AUTO_TRAIN_RETRY" times, it switch to
 step training mode.
 It will more efficiency that finish link auto training,
 include retry, and step training in a work, rather than
 re-schedule train work when each training fail.
-it6505_dump() is remove from link trainig work, it takes too much
+Drop auto_train_retry from it6505 structure,
-time to read all register area, and is not necessary.
+and it6505_dump() is remove from link trainig work,
 it takes too much time to read all register area,
 and is not necessary.
 Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
 ---
- drivers/gpu/drm/bridge/ite-it6505.c | 35 ++++++++++++++++-------------------
+ drivers/gpu/drm/bridge/ite-it6505.c | 40 ++++++++++++++-----------------------
-file changed, 16 insertions(+), 19 deletions(-)
+file changed, 15 insertions(+), 25 deletions(-)
 diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
 index XXXXXXX..XXXXXXX 100644
 --- a/drivers/gpu/drm/bridge/ite-it6505.c
 +++ b/drivers/gpu/drm/bridge/ite-it6505.c
+@@ -XXX,XX +XXX,XX @@ struct it6505 {
+     struct delayed_work hdcp_work;
+     struct work_struct hdcp_wait_ksv_list;
+     struct completion extcon_completion;
+-    u8 auto_train_retry;
+     bool hdcp_desired;
+     bool is_repeater;
+     u8 hdcp_down_stream_count;
 @@ -XXX,XX +XXX,XX @@ static int it6505_get_dpcd(struct it6505 *it6505, int offset, u8 *dpcd, int num)
      return 0;
  }
 -static void it6505_dump(struct it6505 *it6505)
 +static void __maybe_unused it6505_dump(struct it6505 *it6505)
  {
      unsigned int i, j;
      u8 regs[16];
+@@ -XXX,XX +XXX,XX @@ static void it6505_variable_config(struct it6505 *it6505)
+     it6505->lane_count = MAX_LANE_COUNT;
+     it6505->link_state = LINK_IDLE;
+     it6505->hdcp_desired = HDCP_DESIRED;
+-    it6505->auto_train_retry = AUTO_TRAIN_RETRY;
+     it6505->audio.select = AUDIO_SELECT;
+     it6505->audio.sample_rate = AUDIO_SAMPLE_RATE;
+     it6505->audio.channel_count = AUDIO_CHANNEL_COUNT;
 @@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
  {
      struct it6505 *it6505 = container_of(work, struct it6505, link_works);
      struct device *dev = it6505->dev;
 -    int ret;
 ...
 -
 -    if (it6505->auto_train_retry < 1) {
 -        it6505_link_step_train_process(it6505);
 -        return;
 -    }
-+    retry = it6505->auto_train_retry;
+-
-+    do {
+-    ret = it6505_link_start_auto_train(it6505);
 -    DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
 -                 ret ? "pass" : "failed", it6505->auto_train_retry);
 +    for (retry = AUTO_TRAIN_RETRY; retry > 0; retry--) {
 +        it6505_link_training_setup(it6505);
 +        it6505_reset_hdcp(it6505);
 +        it6505_aux_reset(it6505);
--    ret = it6505_link_start_auto_train(it6505);
--    DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
-+        ret = it6505_link_start_auto_train(it6505);
-+        DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
-                  ret ? "pass" : "failed", it6505->auto_train_retry);
-+        if (ret) {
-+            it6505_link_train_ok(it6505);
-+            return;
-+        }
-+    } while (retry--);
 -    if (ret) {
 -        it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 -        it6505_link_train_ok(it6505);
 -    } else {
 -        it6505->auto_train_retry--;
 -        it6505_dump(it6505);
--    }
++        ret = it6505_link_start_auto_train(it6505);
 +        DRM_DEV_DEBUG_DRIVER(dev, "auto train %s,",
 +                     ret ? "pass" : "failed");
 +        if (ret) {
 +            it6505_link_train_ok(it6505);
 +            return;
 +        }
      }
 +    /*After HW auto training fail, try link training step by step*/
 +    it6505_link_step_train_process(it6505);
  }
+ static void it6505_plugged_status_to_codec(struct it6505 *it6505)
+@@ -XXX,XX +XXX,XX @@ static int it6505_process_hpd_irq(struct it6505 *it6505)
+                  (int)ARRAY_SIZE(link_status), link_status);
+     if (!drm_dp_channel_eq_ok(link_status, it6505->lane_count)) {
+-        it6505->auto_train_retry = AUTO_TRAIN_RETRY;
+         it6505_video_reset(it6505);
+     }
+@@ -XXX,XX +XXX,XX @@ static void it6505_irq_hpd(struct it6505 *it6505)
+             it6505_variable_config(it6505);
+             it6505_parse_link_capabilities(it6505);
+         }
+-        it6505->auto_train_retry = AUTO_TRAIN_RETRY;
+         it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
+                          DP_SET_POWER_D0);
+@@ -XXX,XX +XXX,XX @@ static void it6505_irq_video_handler(struct it6505 *it6505, const int *int_statu
+                  (unsigned int *)int_status)) ||
+         (it6505_test_bit(BIT_INT_VID_FIFO_ERROR,
+                  (unsigned int *)int_status))) {
+-        it6505->auto_train_retry = AUTO_TRAIN_RETRY;
+         flush_work(&it6505->link_works);
+         it6505_stop_hdcp(it6505);
+         it6505_video_reset(it6505);
 --
 .34.1

-[PATCH RESEND 3/3] drm/bridge: it6505: skip auto training when previous try fail
+[PATCH v3 5/5] drm/bridge: it6505: skip auto training when previous try fail
 ...
 step training, skip auto training when link training restart,
 usually happen when display resolution is changed.
 Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
 ---
- drivers/gpu/drm/bridge/ite-it6505.c | 36 +++++++++++++++++++++---------------
+ drivers/gpu/drm/bridge/ite-it6505.c | 8 ++++++--
-file changed, 21 insertions(+), 15 deletions(-)
+file changed, 6 insertions(+), 2 deletions(-)
 diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
 index XXXXXXX..XXXXXXX 100644
 --- a/drivers/gpu/drm/bridge/ite-it6505.c
 +++ b/drivers/gpu/drm/bridge/ite-it6505.c
 @@ -XXX,XX +XXX,XX @@ struct it6505 {
+     struct delayed_work hdcp_work;
      struct work_struct hdcp_wait_ksv_list;
      struct completion extcon_completion;
-     u8 auto_train_retry;
 +    u8 step_train_only;
      bool hdcp_desired;
      bool is_repeater;
      u8 hdcp_down_stream_count;
 @@ -XXX,XX +XXX,XX @@ static void it6505_link_step_train_process(struct it6505 *it6505)
 ...
 +    it6505->step_train_only = false;
      it6505->link_state = LINK_IDLE;
      it6505_video_reset(it6505);
  }
 @@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
      if (!it6505_get_sink_hpd_status(it6505))
          return;
--
--    retry = it6505->auto_train_retry;
+-    for (retry = AUTO_TRAIN_RETRY; retry > 0; retry--) {
--    do {
++    for (retry = AUTO_TRAIN_RETRY; retry > 0 && !it6505->step_train_only; retry--) {
--        it6505_link_training_setup(it6505);
+         it6505_link_training_setup(it6505);
--        it6505_reset_hdcp(it6505);
+         it6505_reset_hdcp(it6505);
--        it6505_aux_reset(it6505);
+         it6505_aux_reset(it6505);
--
--        ret = it6505_link_start_auto_train(it6505);
+         ret = it6505_link_start_auto_train(it6505);
--        DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
+         DRM_DEV_DEBUG_DRIVER(dev, "auto train %s,",
--                 ret ? "pass" : "failed", it6505->auto_train_retry);
+-                     ret ? "pass" : "failed");
--        if (ret) {
++                    ret ? "pass" : "failed");
--            it6505_link_train_ok(it6505);
+         if (ret) {
--            return;
+             it6505_link_train_ok(it6505);
--        }
+             return;
 -    } while (retry--);
 +    /* skip auto training if previous auto train is fail*/
 +    if (!it6505->step_train_only) {
 +        retry = it6505->auto_train_retry;
 +        do {
 +            it6505_link_training_setup(it6505);
 +            it6505_reset_hdcp(it6505);
 +            it6505_aux_reset(it6505);
 +
 +            ret = it6505_link_start_auto_train(it6505);
 +            DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
 +                ret ? "pass" : "failed", it6505->auto_train_retry);
 +            if (ret) {
 +                it6505_link_train_ok(it6505);
 +                return;
 +            }
 +        } while (retry--);
 +    }
      /*After HW auto training fail, try link training step by step*/
      it6505_link_step_train_process(it6505);
 @@ -XXX,XX +XXX,XX @@ static void it6505_irq_hpd(struct it6505 *it6505)
+             it6505_variable_config(it6505);
              it6505_parse_link_capabilities(it6505);
          }
-         it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 +        it6505->step_train_only = false;
          it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
                           DP_SET_POWER_D0);
 --
 .34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

IT6505 supports HW link training which will write DPCD and check
training status automatically.

In the case that driver set link rate at 2.7G and HW fail to training,
it will change link configuration and try 1.65G. And this will cause
INT_VID_FIFO_ERROR triggered when link clock is changed.

When video error occurs, video logic is reset and link training restart,
this will cause endless auto link training.

Modify link auto training with disable INT_VID_FIFO_ERROR to avoid loop
and check INT_LINK_TRAIN_FAIL event to abort wait training done.

Since INT_LINK_TRAIN_FAIL is checked when auto training, it is remove
from  it6505_int_threaded_handler()

In order to reset HW link auto training state,
bits FORCE_RETRAIN and MANUAL_TRAIN at REG_TRAIN_CTRL1 must be set
at the same time.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 61 +++++++++++++++++++++++++------------
 1 file changed, 42 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -XXX,XX +XXX,XX @@ static void it6505_int_mask_enable(struct it6505 *it6505)
 	it6505_write(it6505, INT_MASK_02, BIT(INT_AUX_CMD_FAIL) |
 		     BIT(INT_HDCP_KSV_CHECK) | BIT(INT_AUDIO_FIFO_ERROR));
 
-	it6505_write(it6505, INT_MASK_03, BIT(INT_LINK_TRAIN_FAIL) |
+	it6505_write(it6505, INT_MASK_03,
 		     BIT(INT_VID_FIFO_ERROR) | BIT(INT_IO_LATCH_FIFO_OVERFLOW));
 }
 
@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_setup(struct it6505 *it6505)
 
 static bool it6505_link_start_auto_train(struct it6505 *it6505)
 {
-	int timeout = 500, link_training_state;
+	int link_training_state;
 	bool state = false;
+	struct device *dev = it6505->dev;
+	int int03;
+	unsigned long timeout;
+
+	guard(mutex)(&it6505->aux_lock);
+	/* Disable FIFO error interrupt trigger  */
+	/* to prevent training fail loop issue   */
+	it6505_set_bits(it6505, INT_MASK_03, BIT(INT_VID_FIFO_ERROR), 0);
+
+	it6505_write(it6505, INT_STATUS_03,
+		     BIT(INT_LINK_TRAIN_FAIL) | BIT(INT_VID_FIFO_ERROR));
+	int03 = it6505_read(it6505, INT_STATUS_03);
 
-	mutex_lock(&it6505->aux_lock);
 	it6505_set_bits(it6505, REG_TRAIN_CTRL0,
 			FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
-	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
+
+	/* reset link state machine and re start training*/
+	it6505_write(it6505, REG_TRAIN_CTRL1,
+		     FORCE_RETRAIN | MANUAL_TRAIN);
 	it6505_write(it6505, REG_TRAIN_CTRL1, AUTO_TRAIN);
 
-	while (timeout > 0) {
+	timeout = jiffies + msecs_to_jiffies(100) + 1;
+	for (;;) {
 		usleep_range(1000, 2000);
 		link_training_state = it6505_read(it6505, REG_LINK_TRAIN_STS);
+		int03 = it6505_read(it6505, INT_STATUS_03);
+		if (int03 & BIT(INT_LINK_TRAIN_FAIL)) {
+			/* Ignore INT_VID_FIFO_ERROR when auto training fail*/
+			it6505_write(it6505, INT_STATUS_03,
+				     BIT(INT_LINK_TRAIN_FAIL) |
+				     BIT(INT_VID_FIFO_ERROR));
+
+			if (int03 & BIT(INT_VID_FIFO_ERROR)) {
+				DRM_DEV_DEBUG_DRIVER(dev,
+				"video fifo error when training fail (%x)!",
+				int03);
+			}
+
+			break;
+		}
 
 		if (link_training_state > 0 &&
 		    (link_training_state & LINK_STATE_NORP)) {
 			state = true;
-			goto unlock;
+			break;
 		}
 
-		timeout--;
+		if (time_after(jiffies, timeout))
+			break;
 	}
-unlock:
-	mutex_unlock(&it6505->aux_lock);
 
+	/* recover interrupt trigger*/
+	it6505_set_bits(it6505, INT_MASK_03,
+			BIT(INT_VID_FIFO_ERROR), BIT(INT_VID_FIFO_ERROR));
 	return state;
 }
 
@@ -XXX,XX +XXX,XX @@ static void it6505_stop_link_train(struct it6505 *it6505)
 {
 	it6505->link_state = LINK_IDLE;
 	cancel_work_sync(&it6505->link_works);
-	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
+	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN | MANUAL_TRAIN);
 }
 
 static void it6505_link_train_ok(struct it6505 *it6505)
@@ -XXX,XX +XXX,XX @@ static void it6505_irq_audio_fifo_error(struct it6505 *it6505)
 		it6505_enable_audio(it6505);
 }
 
-static void it6505_irq_link_train_fail(struct it6505 *it6505)
-{
-	struct device *dev = it6505->dev;
-
-	DRM_DEV_DEBUG_DRIVER(dev, "link training fail interrupt");
-	schedule_work(&it6505->link_works);
-}
-
 static bool it6505_test_bit(unsigned int bit, const unsigned int *addr)
 {
 	return 1 & (addr[bit / BITS_PER_BYTE] >> (bit % BITS_PER_BYTE));
@@ -XXX,XX +XXX,XX @@ static irqreturn_t it6505_int_threaded_handler(int unused, void *data)
 		{ BIT_INT_AUX_CMD_FAIL, it6505_irq_aux_cmd_fail },
 		{ BIT_INT_HDCP_KSV_CHECK, it6505_irq_hdcp_ksv_check },
 		{ BIT_INT_AUDIO_FIFO_ERROR, it6505_irq_audio_fifo_error },
-		{ BIT_INT_LINK_TRAIN_FAIL, it6505_irq_link_train_fail },
 	};
 	int int_status[3], i;

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

The DP link training work include auto training and after
auto training failed "auto_train_retry" times, it switch to
step training mode.

It will more efficiency that finish link auto training,
include retry, and step training in a work, rather than
re-schedule train work when each training fail.

it6505_dump() is remove from link trainig work, it takes too much
time to read all register area, and is not necessary.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

When connect to device which can only training done by
step training, skip auto training when link training restart,
usually happen when display resolution is changed.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -XXX,XX +XXX,XX @@ struct it6505 {
 	struct work_struct hdcp_wait_ksv_list;
 	struct completion extcon_completion;
 	u8 auto_train_retry;
+	u8 step_train_only;
 	bool hdcp_desired;
 	bool is_repeater;
 	u8 hdcp_down_stream_count;
@@ -XXX,XX +XXX,XX @@ static void it6505_link_step_train_process(struct it6505 *it6505)
 				     ret ? "pass" : "failed", i + 1);
 		if (ret) {
 			it6505_link_train_ok(it6505);
+			it6505->step_train_only = true;
 			return;
 		}
 	}
 
 	DRM_DEV_DEBUG_DRIVER(dev, "training fail");
+	it6505->step_train_only = false;
 	it6505->link_state = LINK_IDLE;
 	it6505_video_reset(it6505);
 }
@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
 
 	if (!it6505_get_sink_hpd_status(it6505))
 		return;
-
-	retry = it6505->auto_train_retry;
-	do {
-		it6505_link_training_setup(it6505);
-		it6505_reset_hdcp(it6505);
-		it6505_aux_reset(it6505);
-
-		ret = it6505_link_start_auto_train(it6505);
-		DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
-			     ret ? "pass" : "failed", it6505->auto_train_retry);
-		if (ret) {
-			it6505_link_train_ok(it6505);
-			return;
-		}
-	} while (retry--);
+	/* skip auto training if previous auto train is fail*/
+	if (!it6505->step_train_only) {
+		retry = it6505->auto_train_retry;
+		do {
+			it6505_link_training_setup(it6505);
+			it6505_reset_hdcp(it6505);
+			it6505_aux_reset(it6505);
+
+			ret = it6505_link_start_auto_train(it6505);
+			DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
+				ret ? "pass" : "failed", it6505->auto_train_retry);
+			if (ret) {
+				it6505_link_train_ok(it6505);
+				return;
+			}
+		} while (retry--);
+	}
 
 	/*After HW auto training fail, try link training step by step*/
 	it6505_link_step_train_process(it6505);
@@ -XXX,XX +XXX,XX @@ static void it6505_irq_hpd(struct it6505 *it6505)
 			it6505_parse_link_capabilities(it6505);
 		}
 		it6505->auto_train_retry = AUTO_TRAIN_RETRY;
+		it6505->step_train_only = false;
 
 		it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
 					     DP_SET_POWER_D0);

-- 
2.34.1

IT6505 supports HW auto link training which will write DPCD and check
training status automatically. Some DP device can not pass
HW auto link training and must set link training step by step.

when HW auto link training fail, it may trigger video FIFO error,
and link training process will reset to beginning, and never try
step training method.

Modify training method improve compatibility to these DP devices.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
Changes in v3:
- Patch 1/5 : add commit message for detial about changes
- Patch 2/5 : fix lost variable struct device *dev;
- Patch 3/5 : keep changes and remove refactoring
- Patch 5/5 : merge condition "it6505->step_train_only" check form if condiction into for loop.
- Link to v2: https://lore.kernel.org/r/20250326-fix-link-training-v2-0-756c8306f500@ite.com.tw

Changes in v2:
- 1. Split [PATCH 1/3] into 3 commits
- 2. Drop non necessary variable auto_ttrain_retry
- Link to v1: https://lore.kernel.org/all/20250318-fix-link-training-v1-0-19266711142c@ite.com.tw/

---
Hermes Wu (5):
      drm/bridge: it6505: fix link training state HW register reset
      drm/bridge: it6505: check INT_LINK_TRAIN_FAIL while link auto training
      drm/bridge: it6505: modify DP link auto training
      drm/bridge: it6505: modify DP link training work
      drm/bridge: it6505: skip auto training when previous try fail

drivers/gpu/drm/bridge/ite-it6505.c | 88 +++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 38 deletions(-)
---
base-commit: 938fbb16aba8f7b88e0fdcf56f315a5bbad41aad
change-id: 20250121-fix-link-training-461495494655

Best regards,
-- 
Hermes Wu <Hermes.wu@ite.com.tw>

From: Hermes Wu <Hermes.wu@ite.com.tw>

When connect to a DP-to-HDMI device which does not connect
to HDMI sink, it will report DPCD 00200h with SINK_COUNT = "0",
and issue HPD_IRQ when SINK_COUNT change to "1".

IT6505 can not recive HPD_IRQ before training done and driver will
force HW enter training done state when connect to such devices.

When HW is force to training done state and restart link training,
bits FORCE_RETRAIN and MANUAL_TRAIN at REG_TRAIN_CTRL1 must be set
at the same time to reset HW state.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

When start link training, interrupt status INT_LINK_TRAIN_FAIL can
use to check link training fail and no need to wait until timeout.

it6505_irq_link_train_fail() remove from interrupt and no longer used.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

IT6505 supports HW link training which will write DPCD and check
training status automatically.

In the case that driver set link rate at 2.7G and HW fail to training,
it will change link configuration and try 1.65G. And this will cause
INT_VID_FIFO_ERROR triggered when link clock is changed.

When video error occurs, video logic is reset and link training restart,
this will cause endless auto link training.

Modify link auto training with disable INT_VID_FIFO_ERROR to avoid loop
and check INT_LINK_TRAIN_FAIL event to abort wait training done.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

The DP link training work include auto training and after
auto training failed "AUTO_TRAIN_RETRY" times, it switch to
step training mode.

It will more efficiency that finish link auto training,
include retry, and step training in a work, rather than
re-schedule train work when each training fail.

Drop auto_train_retry from it6505 structure,
and it6505_dump() is remove from link trainig work,
it takes too much time to read all register area,
and is not necessary.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 40 ++++++++++++++-----------------------
 1 file changed, 15 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -XXX,XX +XXX,XX @@ struct it6505 {
 	struct delayed_work hdcp_work;
 	struct work_struct hdcp_wait_ksv_list;
 	struct completion extcon_completion;
-	u8 auto_train_retry;
 	bool hdcp_desired;
 	bool is_repeater;
 	u8 hdcp_down_stream_count;
@@ -XXX,XX +XXX,XX @@ static int it6505_get_dpcd(struct it6505 *it6505, int offset, u8 *dpcd, int num)
 	return 0;
 }
 
-static void it6505_dump(struct it6505 *it6505)
+static void __maybe_unused it6505_dump(struct it6505 *it6505)
 {
 	unsigned int i, j;
 	u8 regs[16];
@@ -XXX,XX +XXX,XX @@ static void it6505_variable_config(struct it6505 *it6505)
 	it6505->lane_count = MAX_LANE_COUNT;
 	it6505->link_state = LINK_IDLE;
 	it6505->hdcp_desired = HDCP_DESIRED;
-	it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 	it6505->audio.select = AUDIO_SELECT;
 	it6505->audio.sample_rate = AUDIO_SAMPLE_RATE;
 	it6505->audio.channel_count = AUDIO_CHANNEL_COUNT;
@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
 {
 	struct it6505 *it6505 = container_of(work, struct it6505, link_works);
 	struct device *dev = it6505->dev;
-	int ret;
+	int ret, retry;
 
 	DRM_DEV_DEBUG_DRIVER(dev, "it6505->sink_count: %d",
 			     it6505->sink_count);
@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
 	if (!it6505_get_sink_hpd_status(it6505))
 		return;
 
-	it6505_link_training_setup(it6505);
-	it6505_reset_hdcp(it6505);
-	it6505_aux_reset(it6505);
-
-	if (it6505->auto_train_retry < 1) {
-		it6505_link_step_train_process(it6505);
-		return;
-	}
-
-	ret = it6505_link_start_auto_train(it6505);
-	DRM_DEV_DEBUG_DRIVER(dev, "auto train %s, auto_train_retry: %d",
-			     ret ? "pass" : "failed", it6505->auto_train_retry);
+	for (retry = AUTO_TRAIN_RETRY; retry > 0; retry--) {
+		it6505_link_training_setup(it6505);
+		it6505_reset_hdcp(it6505);
+		it6505_aux_reset(it6505);
 
-	if (ret) {
-		it6505->auto_train_retry = AUTO_TRAIN_RETRY;
-		it6505_link_train_ok(it6505);
-	} else {
-		it6505->auto_train_retry--;
-		it6505_dump(it6505);
+		ret = it6505_link_start_auto_train(it6505);
+		DRM_DEV_DEBUG_DRIVER(dev, "auto train %s,",
+				     ret ? "pass" : "failed");
+		if (ret) {
+			it6505_link_train_ok(it6505);
+			return;
+		}
 	}
 
+	/*After HW auto training fail, try link training step by step*/
+	it6505_link_step_train_process(it6505);
 }
 
 static void it6505_plugged_status_to_codec(struct it6505 *it6505)
@@ -XXX,XX +XXX,XX @@ static int it6505_process_hpd_irq(struct it6505 *it6505)
 			     (int)ARRAY_SIZE(link_status), link_status);
 
 	if (!drm_dp_channel_eq_ok(link_status, it6505->lane_count)) {
-		it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 		it6505_video_reset(it6505);
 	}
 
@@ -XXX,XX +XXX,XX @@ static void it6505_irq_hpd(struct it6505 *it6505)
 			it6505_variable_config(it6505);
 			it6505_parse_link_capabilities(it6505);
 		}
-		it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 
 		it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
 					     DP_SET_POWER_D0);
@@ -XXX,XX +XXX,XX @@ static void it6505_irq_video_handler(struct it6505 *it6505, const int *int_statu
 			     (unsigned int *)int_status)) ||
 	    (it6505_test_bit(BIT_INT_VID_FIFO_ERROR,
 			     (unsigned int *)int_status))) {
-		it6505->auto_train_retry = AUTO_TRAIN_RETRY;
 		flush_work(&it6505->link_works);
 		it6505_stop_hdcp(it6505);
 		it6505_video_reset(it6505);

-- 
2.34.1

From: Hermes Wu <Hermes.wu@ite.com.tw>

When connect to device which can only training done by
step training, skip auto training when link training restart,
usually happen when display resolution is changed.

Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -XXX,XX +XXX,XX @@ struct it6505 {
 	struct delayed_work hdcp_work;
 	struct work_struct hdcp_wait_ksv_list;
 	struct completion extcon_completion;
+	u8 step_train_only;
 	bool hdcp_desired;
 	bool is_repeater;
 	u8 hdcp_down_stream_count;
@@ -XXX,XX +XXX,XX @@ static void it6505_link_step_train_process(struct it6505 *it6505)
 				     ret ? "pass" : "failed", i + 1);
 		if (ret) {
 			it6505_link_train_ok(it6505);
+			it6505->step_train_only = true;
 			return;
 		}
 	}
 
 	DRM_DEV_DEBUG_DRIVER(dev, "training fail");
+	it6505->step_train_only = false;
 	it6505->link_state = LINK_IDLE;
 	it6505_video_reset(it6505);
 }
@@ -XXX,XX +XXX,XX @@ static void it6505_link_training_work(struct work_struct *work)
 	if (!it6505_get_sink_hpd_status(it6505))
 		return;
 
-	for (retry = AUTO_TRAIN_RETRY; retry > 0; retry--) {
+	for (retry = AUTO_TRAIN_RETRY; retry > 0 && !it6505->step_train_only; retry--) {
 		it6505_link_training_setup(it6505);
 		it6505_reset_hdcp(it6505);
 		it6505_aux_reset(it6505);
 
 		ret = it6505_link_start_auto_train(it6505);
 		DRM_DEV_DEBUG_DRIVER(dev, "auto train %s,",
-				     ret ? "pass" : "failed");
+					ret ? "pass" : "failed");
 		if (ret) {
 			it6505_link_train_ok(it6505);
 			return;
@@ -XXX,XX +XXX,XX @@ static void it6505_irq_hpd(struct it6505 *it6505)
 			it6505_variable_config(it6505);
 			it6505_parse_link_capabilities(it6505);
 		}
+		it6505->step_train_only = false;
 
 		it6505_drm_dp_link_set_power(&it6505->aux, &it6505->link,
 					     DP_SET_POWER_D0);

-- 
2.34.1