From nobody Mon Jun 8 18:58:39 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8952632AAC5 for ; Wed, 27 May 2026 14:04:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779890684; cv=pass; b=EIC14l78BdjNWIwr9e0pJF/DdCUTfJOxYs41cuCv2QGDYg/eLdRLw6RTPd2XF/3EcJo+JTm27mUvo/BArlDBJBDxiL2DMJD/WnZi4vZLffyPq7bq18BwjhypvtsZG6Fi2geUr9NVUOka1xmPmx6HQ6sqeQBw83CocBC6KVXDjnM= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779890684; c=relaxed/simple; bh=oMExSX5XjU5sJph5AokxZ8NHj38BCqS6YCU7Pi5050o=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=toyHWnGX7Q/z1giJij+YNyv9RLy2+jsmF8ocK6VAb8gXk67LQ/ljdVwWmTu6CcNrKUNTv9wYjauhGvWsyib3TkF0vJcu2Me6pr7jZvBZSTsteEnHxhTuKlzY92o2RjbmOorE936TbF9zh9ezFOCCduOy0WWrYutZlZKEscVNCPU= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=nicolas.frattaroli@collabora.com header.b=h4oOX0/g; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=nicolas.frattaroli@collabora.com header.b="h4oOX0/g" ARC-Seal: i=1; a=rsa-sha256; t=1779890647; cv=none; d=zohomail.com; s=zohoarc; b=Xz4i/ebKuyf6caCw+CVxi/qlAuSMIKGK5vMBqalHJSlk7sX0QslxPkCBkHuuBevZuGL0VtHiUvNPkdRggPA4Pcjr9GBtlCFYryDXCbsi3PDUQj+IBFAVxR9QlOscLSXNEH2UvYeO4kUlPl0nX3xt6CG0OMw0rTXbGHZzi92UhlQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1779890647; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=FJVCfsO9fR1MMtto28iRXIlsu49zY0/C29vsmsa+GMU=; b=OrGJ8DduJUpll5I6uTYZad5DCAS+JTg9H+xBirfvC62bVvOsYgqRLChasHdBZ8ET4H+68RapjoHCkVYKH8gTZdutvdkvMSgd9DXXn5+sDNUqiKwpR+ap/XadkJRUPC6CMowhrLT6chMktAW5miV62frXJ3/yU3/7+pQcu9+1xYY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=nicolas.frattaroli@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1779890647; s=zohomail; d=collabora.com; i=nicolas.frattaroli@collabora.com; h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:References:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=FJVCfsO9fR1MMtto28iRXIlsu49zY0/C29vsmsa+GMU=; b=h4oOX0/gUvxzehYAZRplhydQWyQDP6XGl9ZRG9Hf9m/jesbXP44TiPLmMfs2sOaE CcFDKLsrG4VoRGKTl6QowLiJ4jSEv0EAQdYhLDzXJWEK1pceaCtxfDiTLu1eQPnZx/t 9wd/P8adIdcF+3mj1YTJQ2IHFMU3SZ6bRF3pNxMg= Received: by mx.zohomail.com with SMTPS id 177989064625077.556391634428; Wed, 27 May 2026 07:04:06 -0700 (PDT) From: Nicolas Frattaroli Date: Wed, 27 May 2026 16:03:42 +0200 Subject: [PATCH v4 1/4] drm/scdc-helper: Don't use ssize_t return type for scdc_read/write Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-scdc-link-health-v4-1-622ea40a1f59@collabora.com> References: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> In-Reply-To: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> To: Jani Nikula , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Daniel Stone Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Nicolas Frattaroli X-Mailer: b4 0.15.2 drm_scdc_read and drm_scdc_write, both of which are only used within drm_scdc_helper (although exported), use a ssize_t as their return type. This would make sense if they returned the number of bytes read/written on success, and negative errno otherwise. However, they return 0 on success. Demote them to "int" as their return type, in order to avoid needlessly using 64 bits when less suffices. No functional change. Reviewed-by: Luca Ceresoli Signed-off-by: Nicolas Frattaroli Reviewed-by: Hans Verkuil --- drivers/gpu/drm/display/drm_scdc_helper.c | 8 ++++---- include/drm/display/drm_scdc_helper.h | 8 ++++---- 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/display/drm_scdc_helper.c b/drivers/gpu/drm/di= splay/drm_scdc_helper.c index df878aad4a36..8403f2390ab6 100644 --- a/drivers/gpu/drm/display/drm_scdc_helper.c +++ b/drivers/gpu/drm/display/drm_scdc_helper.c @@ -67,8 +67,8 @@ * Returns: * 0 on success, negative error code on failure. */ -ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, - size_t size) +int drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, + size_t size) { int ret; struct i2c_msg msgs[2] =3D { @@ -107,8 +107,8 @@ EXPORT_SYMBOL(drm_scdc_read); * Returns: * 0 on success, negative error code on failure. */ -ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset, - const void *buffer, size_t size) +int drm_scdc_write(struct i2c_adapter *adapter, u8 offset, const void *buf= fer, + size_t size) { struct i2c_msg msg =3D { .addr =3D SCDC_I2C_SLAVE_ADDRESS, diff --git a/include/drm/display/drm_scdc_helper.h b/include/drm/display/dr= m_scdc_helper.h index 34600476a1b9..e9ccaeba56dd 100644 --- a/include/drm/display/drm_scdc_helper.h +++ b/include/drm/display/drm_scdc_helper.h @@ -31,10 +31,10 @@ struct drm_connector; struct i2c_adapter; =20 -ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, - size_t size); -ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset, - const void *buffer, size_t size); +int drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, + size_t size); +int drm_scdc_write(struct i2c_adapter *adapter, u8 offset, const void *buf= fer, + size_t size); =20 /** * drm_scdc_readb - read a single byte from SCDC --=20 2.54.0 From nobody Mon Jun 8 18:58:39 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 893DE3246EB for ; Wed, 27 May 2026 14:04:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779890684; cv=pass; b=ubzQW+ccwghvDLV/QX38yBT50VLYuHswtGgzz6amAEc/RTyng/iykJwyr2d9PQ65tcfe5BhHY+LHKHHar0/V5NfWDoszDrUfzhOdT3t25U2eRSFMeyK1lEVQH1Kk8dX94TUPag07k3mZG2PrhCt67bDj+FhtYn8k862UJV2yB0Y= ARC-Message-Signature: i=2; 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h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:References:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=AePNlg/tPONqMp07nxRxcyXDUmpSdhz9BPkGf90Crqs=; b=F0TOpfs/GgObbMlbXejubESD84tHDGYkalcfjte1kut13LlZ4bGIu6Z3XEIAwPRD LXT9TfpG3J/1Vg57WFtaPk5xsH5S5af65BhaMXHtDYoAKSyUX2OQOWEx23O9rf6ApcU sEzOj+7pp9/SayyYtMiA5P6X06JOBONFJrSQWZhk= Received: by mx.zohomail.com with SMTPS id 1779890650636147.08368009246385; Wed, 27 May 2026 07:04:10 -0700 (PDT) From: Nicolas Frattaroli Date: Wed, 27 May 2026 16:03:43 +0200 Subject: [PATCH v4 2/4] drm/scdc-helper: Add scdc_status debugfs entry Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-scdc-link-health-v4-2-622ea40a1f59@collabora.com> References: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> In-Reply-To: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> To: Jani Nikula , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Daniel Stone Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Nicolas Frattaroli X-Mailer: b4 0.15.2 SCDC provides status information on the current display link. At the very least, it may be useful to expose this info through debugfs. Add a debugfs entry for it under the connector, which displays a few more details parsed out of the SCDC registers. A new drm_scdc_debugfs_init function can be called by the connector implementation to initialise the debugfs file. Signed-off-by: Nicolas Frattaroli --- drivers/gpu/drm/display/drm_scdc_helper.c | 237 ++++++++++++++++++++++++++= ++++ include/drm/display/drm_scdc_helper.h | 32 ++++ 2 files changed, 269 insertions(+) diff --git a/drivers/gpu/drm/display/drm_scdc_helper.c b/drivers/gpu/drm/di= splay/drm_scdc_helper.c index 8403f2390ab6..7739fb5e77a1 100644 --- a/drivers/gpu/drm/display/drm_scdc_helper.c +++ b/drivers/gpu/drm/display/drm_scdc_helper.c @@ -24,11 +24,14 @@ #include #include #include +#include #include +#include =20 #include #include #include +#include #include =20 /** @@ -55,6 +58,11 @@ =20 #define SCDC_I2C_SLAVE_ADDRESS 0x54 =20 +struct scdc_debugfs_priv { + struct drm_connector *connector; + struct drm_scdc_state state; +}; + /** * drm_scdc_read - read a block of data from SCDC * @adapter: I2C controller @@ -276,3 +284,232 @@ bool drm_scdc_set_high_tmds_clock_ratio(struct drm_co= nnector *connector, return true; } EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio); + +/** + * drm_scdc_read_status0_flags - Read SCDC "Status Flags" Register + * @connector: pointer to &struct drm_connector to issue the scdc request = on + * @flags: pointer to the caller's &struct drm_scdc_status_flags to output= to + * + * Reads the SCDC Status Flags 0 register, and outputs its contents to the + * destination @flags. Contents of @flags are only valid if function retur= ns 0. + * + * Returns: %0 on success, negative errno on error. + */ +int drm_scdc_read_status0_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags) +{ + int ret; + u8 val; + + ret =3D drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_STATUS_UPDATE= ); + if (ret) + return ret; + + ret =3D drm_scdc_readb(connector->ddc, SCDC_STATUS_FLAGS_0, &val); + if (ret) + return ret; + + flags->clock_detected =3D val & SCDC_CLOCK_DETECT; + flags->ch0_locked =3D val & SCDC_CH0_LOCK; + flags->ch1_locked =3D val & SCDC_CH1_LOCK; + flags->ch2_locked =3D val & SCDC_CH2_LOCK; + + return 0; +} +EXPORT_SYMBOL(drm_scdc_read_status0_flags); + +/** + * drm_scdc_read_error_counters - Read and clear SCDC error counters + * @connector: pointer to &struct drm_connector to issue the scdc request = on + * @counter: Caller's u16 array with 3 elements to write the counter value= s into + * + * Read the SCDC channel error counters. If the count of channel *n* is va= lid, + * write it into counter[n]. Otherwise, set counter[n] to 0. Reads all cou= nters + * in one read chunk, then clears every counter, as is mandated. + * + * Returns: %0 on success, negative errno on error. + */ +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[3]) +{ + u8 buf[7] =3D {}; + int ret; + u8 sum =3D 0; + int i; + + ret =3D drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_CED_UPDATE); + if (ret) + return ret; + + ret =3D drm_scdc_read(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(b= uf)); + if (ret) + return ret; + + /* + * Verify the "checksum", i.e. sum up everything including the checksum + * register as a wrapping unsigned 8-bit addition and verify it's 0. + */ + for (i =3D 0; i < ARRAY_SIZE(buf); i++) + sum =3D wrapping_add(u8, sum, buf[i]); + + if (sum) + return -EPROTO; + + for (i =3D 0; i < ARRAY_SIZE(buf) - 1; i +=3D 2) { + if (buf[i + 1] & SCDC_CHANNEL_VALID) + counter[i / 2] =3D buf[i] | (buf[i + 1] & ~SCDC_CHANNEL_VALID) << 8; + else + counter[i / 2] =3D 0; + + buf[i] =3D 0; + buf[i + 1] =3D 0; + } + buf[ARRAY_SIZE(buf) - 1] =3D 0; + + return drm_scdc_write(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(b= uf)); +} +EXPORT_SYMBOL(drm_scdc_read_error_counters); + +/** + * drm_scdc_read_state - Update state from SCDC + * @connector: pointer to a &struct drm_connector on which to operate on + * @state: pointer to a &struct drm_scdc_state to fill + * + * Reads update flags from SCDC, and updates the parts of @state that SCDC + * claims have changed, as well as populating those where such a distincti= on + * can't be made. + * + * Returns: %0 on success, negative errno on failure. + */ +int drm_scdc_read_state(struct drm_connector *connector, struct drm_scdc_s= tate *state) +{ + u8 upd_flags[2] =3D {}; + struct i2c_adapter *ddc; + struct drm_scdc *scdc; + int ret; + u8 val; + + if (!state || !connector) + return -ENODEV; + + scdc =3D &connector->display_info.hdmi.scdc; + ddc =3D connector->ddc; + + if (!scdc->supported) + return -EOPNOTSUPP; + + ret =3D drm_scdc_readb(ddc, SCDC_TMDS_CONFIG, &val); + if (ret) + return ret; + + state->scrambling_enabled =3D val & SCDC_SCRAMBLING_ENABLE; + state->tmds_bclk_x40 =3D val & SCDC_TMDS_BIT_CLOCK_RATIO_BY_40; + + state->scrambling_detected =3D drm_scdc_get_scrambling_status(connector); + + ret =3D drm_scdc_read(ddc, SCDC_UPDATE_0, &upd_flags, sizeof(upd_flags)); + if (ret) + return ret; + + if (upd_flags[0] & SCDC_STATUS_UPDATE) { + ret =3D drm_scdc_read_status0_flags(connector, &state->stf); + if (ret) + return ret; + } + + if (upd_flags[0] & SCDC_CED_UPDATE) { + ret =3D drm_scdc_read_error_counters(connector, state->error_count); + if (ret) + return ret; + } + + return 0; +} +EXPORT_SYMBOL(drm_scdc_read_state); + +#define scdc_print_str(_f, key, s) \ + (seq_printf((_f), "%-30s: %s\n", (key), (s))) +#define scdc_print_flag(_f, key, val) \ + (scdc_print_str((_f), (key), str_yes_no((val)))) +#define scdc_print_dec(_f, key, val) \ + (seq_printf((_f), "%-30s: %d\n", (key), (val))) + +static int scdc_status_show(struct seq_file *m, void *data) +{ + struct scdc_debugfs_priv *priv =3D m->private; + struct drm_scdc_state *st =3D &priv->state; + struct drm_connector *connector =3D priv->connector; + struct drm_scdc *scdc =3D &connector->display_info.hdmi.scdc; + int ret; + + drm_connector_get(connector); + + if (connector->status !=3D connector_status_connected) { + ret =3D -ENODEV; + goto err_conn_put; + } + + scdc_print_flag(m, "SCDC Supported", scdc->supported); + if (!scdc->supported) { + ret =3D 0; + goto err_conn_put; + } + + scdc_print_flag(m, "Sink Read Request Capable", scdc->read_request); + scdc_print_flag(m, "Scrambling Supported", scdc->scrambling.supported); + scdc_print_flag(m, "Low Rate Scrambling Supported", scdc->scrambling.low_= rates); + + ret =3D drm_scdc_read_state(connector, st); + drm_connector_put(connector); + if (ret) + return ret; + + scdc_print_flag(m, "Scrambling Enabled", st->scrambling_enabled); + scdc_print_flag(m, "Scrambling Detected", st->scrambling_detected); + + if (st->tmds_bclk_x40) + scdc_print_str(m, "TMDS Bit Clock Ratio", "1/40"); + else + scdc_print_str(m, "TMDS Bit Clock Ratio", "1/10"); + + scdc_print_flag(m, "Clock Detected", st->stf.clock_detected); + scdc_print_flag(m, "Channel 0 Locked", st->stf.ch0_locked); + scdc_print_flag(m, "Channel 1 Locked", st->stf.ch1_locked); + scdc_print_flag(m, "Channel 2 Locked", st->stf.ch2_locked); + + scdc_print_dec(m, "Channel 0 Errors", st->error_count[0]); + scdc_print_dec(m, "Channel 1 Errors", st->error_count[1]); + scdc_print_dec(m, "Channel 2 Errors", st->error_count[2]); + + return 0; + +err_conn_put: + drm_connector_put(connector); + + return ret; +} +DEFINE_SHOW_ATTRIBUTE(scdc_status); + +/** + * drm_scdc_debugfs_init - Initialize scdc files in connector debugfs + * @connector: pointer to &struct drm_connector to operate on + * @root: debugfs &struct dentry for the debugfs root of @connector + * + * Creates SCDC-related debugfs files for @connector. Must be called after + * @root is already created. + */ +void drm_scdc_debugfs_init(struct drm_connector *connector, struct dentry = *root) +{ + struct scdc_debugfs_priv *priv; + + if (!root || !connector) + return; + + priv =3D drmm_kzalloc(connector->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return; + + priv->connector =3D connector; + + debugfs_create_file("scdc_status", 0444, root, priv, &scdc_status_fops); +} +EXPORT_SYMBOL(drm_scdc_debugfs_init); diff --git a/include/drm/display/drm_scdc_helper.h b/include/drm/display/dr= m_scdc_helper.h index e9ccaeba56dd..3b3a4e0e48ba 100644 --- a/include/drm/display/drm_scdc_helper.h +++ b/include/drm/display/drm_scdc_helper.h @@ -30,6 +30,31 @@ =20 struct drm_connector; struct i2c_adapter; +struct dentry; + +struct drm_scdc_status_flags { + /* Status Register 0 */ + bool clock_detected; + bool ch0_locked; + bool ch1_locked; + bool ch2_locked; +}; + +struct drm_scdc_state { + /** @stf: contents of the status flag registers */ + struct drm_scdc_status_flags stf; + /** @scramling_enabled: true if TMDS scrambling is on */ + bool scrambling_enabled; + /** @scrambling_detected: true if the sink actually detected scrambling */ + bool scrambling_detected; + /** + * @tmds_bclk_x40: true if TMDS bit period is 1/40th of the TMDS + * clock period, false if it's 1/10th of the clock period. + */ + bool tmds_bclk_x40; + /** @error_count: character error counts for each channel */ + u16 error_count[3]; +}; =20 int drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, size_t size); @@ -77,4 +102,11 @@ bool drm_scdc_get_scrambling_status(struct drm_connecto= r *connector); bool drm_scdc_set_scrambling(struct drm_connector *connector, bool enable); bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, b= ool set); =20 +int drm_scdc_read_status0_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags); +int drm_scdc_read_state(struct drm_connector *connector, + struct drm_scdc_state *state); +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[3]); 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Wed, 27 May 2026 07:04:15 -0700 (PDT) From: Nicolas Frattaroli Date: Wed, 27 May 2026 16:03:44 +0200 Subject: [PATCH v4 3/4] drm/display: bridge_connector: init scdc debugfs for HDMI Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-scdc-link-health-v4-3-622ea40a1f59@collabora.com> References: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> In-Reply-To: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> To: Jani Nikula , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Daniel Stone Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Nicolas Frattaroli , Daniel Stone X-Mailer: b4 0.15.2 On drm_bridge_connectors that contain an HDMI bridge, initialise the SCDC debugfs entry under the connector's debugfs root. Reviewed-by: Daniel Stone Signed-off-by: Nicolas Frattaroli Reviewed-by: Hans Verkuil --- drivers/gpu/drm/display/drm_bridge_connector.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/d= rm/display/drm_bridge_connector.c index 649969fca141..8c2c890bd95d 100644 --- a/drivers/gpu/drm/display/drm_bridge_connector.c +++ b/drivers/gpu/drm/display/drm_bridge_connector.c @@ -25,6 +25,7 @@ #include #include #include +#include =20 /** * DOC: overview @@ -263,6 +264,9 @@ static void drm_bridge_connector_debugfs_init(struct dr= m_connector *connector, if (bridge->funcs->debugfs_init) bridge->funcs->debugfs_init(bridge, root); } + + if (bridge_connector->bridge_hdmi) + drm_scdc_debugfs_init(connector, root); } =20 static void drm_bridge_connector_reset(struct drm_connector *connector) --=20 2.54.0 From nobody Mon Jun 8 18:58:39 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 94EA231E832 for ; 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charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-scdc-link-health-v4-4-622ea40a1f59@collabora.com> References: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> In-Reply-To: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> To: Jani Nikula , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Daniel Stone Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Nicolas Frattaroli X-Mailer: b4 0.15.2 HDMI 2.1 redefines previously reserved fields in SCDC for various new uses. No version check needs to be performed, as an HDMI 2.0 sink's reserved SCDC fields are well-defined to be 0, and any zero-ness of these fields for an HDMI 2.0 sink is not a surprise for SCDC parsers for HDMI 2.1. Implement reading and outputting these fields over debugfs. Signed-off-by: Nicolas Frattaroli Reviewed-by: Hans Verkuil --- drivers/gpu/drm/display/drm_scdc_helper.c | 164 ++++++++++++++++++++++++++= +--- include/drm/display/drm_scdc.h | 16 ++- include/drm/display/drm_scdc_helper.h | 71 ++++++++++++- 3 files changed, 231 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/drm/display/drm_scdc_helper.c b/drivers/gpu/drm/di= splay/drm_scdc_helper.c index 7739fb5e77a1..6e2ad335296e 100644 --- a/drivers/gpu/drm/display/drm_scdc_helper.c +++ b/drivers/gpu/drm/display/drm_scdc_helper.c @@ -21,6 +21,7 @@ * DEALINGS IN THE SOFTWARE. */ =20 +#include #include #include #include @@ -63,6 +64,38 @@ struct scdc_debugfs_priv { struct drm_scdc_state state; }; =20 +static const char *drm_scdc_frl_rate_str(enum drm_scdc_frl_rate rate) +{ + switch (rate) { + case SCDC_FRL_RATE_OFF: + return "Off"; + case SCDC_FRL_RATE_3X3: + return "3 Gbit/s x 3 lanes"; + case SCDC_FRL_RATE_6X3: + return "6 Gbit/s x 3 lanes"; + case SCDC_FRL_RATE_6X4: + return "6 Gbit/s x 4 lanes"; + case SCDC_FRL_RATE_8X4: + return "8 Gbit/s x 4 lanes"; + case SCDC_FRL_RATE_10X4: + return "10 Gbit/s x 4 lanes"; + case SCDC_FRL_RATE_12X4: + return "12 Gbit/s x 4 lanes"; + case SCDC_FRL_RATE_RESV_7: + case SCDC_FRL_RATE_RESV_8: + case SCDC_FRL_RATE_RESV_9: + case SCDC_FRL_RATE_RESV_10: + case SCDC_FRL_RATE_RESV_11: + case SCDC_FRL_RATE_RESV_12: + case SCDC_FRL_RATE_RESV_13: + case SCDC_FRL_RATE_RESV_14: + case SCDC_FRL_RATE_RESV_15: + return "(Reserved)"; + default: + return NULL; + } +} + /** * drm_scdc_read - read a block of data from SCDC * @adapter: I2C controller @@ -313,15 +346,72 @@ int drm_scdc_read_status0_flags(struct drm_connector = *connector, flags->ch0_locked =3D val & SCDC_CH0_LOCK; flags->ch1_locked =3D val & SCDC_CH1_LOCK; flags->ch2_locked =3D val & SCDC_CH2_LOCK; + flags->ln3_locked =3D val & SCDC_LN3_LOCK; + flags->flt_ready =3D val & SCDC_FLT_READY; + flags->dsc_fail =3D val & SCDC_DSC_FAIL; =20 return 0; } EXPORT_SYMBOL(drm_scdc_read_status0_flags); =20 +/** + * drm_scdc_read_status1_2_flags - Read SCDC "Status Flags" 1 and 2 Regist= ers + * @connector: pointer to &struct drm_connector to issue the scdc request = on + * @flags: pointer to the caller's &struct drm_scdc_status_flags to output= to + * + * Reads the SCDC Status Flags 1 and 2 registers, and outputs their conten= ts to + * the destination @flags. Contents of @flags are only valid if function r= eturns + * 0. + * + * Returns 0 on success, negative errno on error. + */ +int drm_scdc_read_status1_2_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags) +{ + u8 val[2] =3D {}; + int ret; + + ret =3D drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_FLT_UPDATE); + if (ret) + return ret; + + ret =3D drm_scdc_read(connector->ddc, SCDC_STATUS_FLAGS_1, val, 2); + if (ret) + return ret; + + flags->ln0_training_pattern =3D FIELD_GET(SCDC_LN_EVEN_TRAIN_PTRN, val[0]= ); + flags->ln1_training_pattern =3D FIELD_GET(SCDC_LN_ODD_TRAIN_PTRN, val[0]); + + flags->ln2_training_pattern =3D FIELD_GET(SCDC_LN_EVEN_TRAIN_PTRN, val[1]= ); + flags->ln3_training_pattern =3D FIELD_GET(SCDC_LN_ODD_TRAIN_PTRN, val[1]); + + return 0; +} +EXPORT_SYMBOL(drm_scdc_read_status1_2_flags); + +#define ERR_DET_OFF(x) ((x) - SCDC_ERR_DET_0_L) + +static int scdc_err_cnt_buf_idx(unsigned int lane) +{ + switch (lane) { + case 0: + return ERR_DET_OFF(SCDC_ERR_DET_0_L); + case 1: + return ERR_DET_OFF(SCDC_ERR_DET_1_L); + case 2: + return ERR_DET_OFF(SCDC_ERR_DET_2_L); + case 3: + return ERR_DET_OFF(SCDC_ERR_DET_3_L); + default: + return -EINVAL; + } +} + /** * drm_scdc_read_error_counters - Read and clear SCDC error counters * @connector: pointer to &struct drm_connector to issue the scdc request = on - * @counter: Caller's u16 array with 3 elements to write the counter value= s into + * @counter: Caller's u16 array with 4 elements to write the counter value= s into + * @num_lanes: number of active lanes, either 3 or 4 * * Read the SCDC channel error counters. If the count of channel *n* is va= lid, * write it into counter[n]. Otherwise, set counter[n] to 0. Reads all cou= nters @@ -329,18 +419,31 @@ EXPORT_SYMBOL(drm_scdc_read_status0_flags); * * Returns: %0 on success, negative errno on error. */ -int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[3]) +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[4], + unsigned int num_lanes) { - u8 buf[7] =3D {}; + unsigned int buf_sz; + u8 buf[9] =3D {}; int ret; u8 sum =3D 0; - int i; + int i, idx; + + switch (num_lanes) { + case 3: + buf_sz =3D 7; + break; + case 4: + buf_sz =3D 9; + break; + default: + return -EINVAL; + } =20 ret =3D drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_CED_UPDATE); if (ret) return ret; =20 - ret =3D drm_scdc_read(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(b= uf)); + ret =3D drm_scdc_read(connector->ddc, SCDC_ERR_DET_0_L, buf, buf_sz); if (ret) return ret; =20 @@ -348,24 +451,23 @@ int drm_scdc_read_error_counters(struct drm_connector= *connector, u16 counter[3] * Verify the "checksum", i.e. sum up everything including the checksum * register as a wrapping unsigned 8-bit addition and verify it's 0. */ - for (i =3D 0; i < ARRAY_SIZE(buf); i++) + for (i =3D 0; i < buf_sz; i++) sum =3D wrapping_add(u8, sum, buf[i]); =20 if (sum) return -EPROTO; =20 - for (i =3D 0; i < ARRAY_SIZE(buf) - 1; i +=3D 2) { - if (buf[i + 1] & SCDC_CHANNEL_VALID) - counter[i / 2] =3D buf[i] | (buf[i + 1] & ~SCDC_CHANNEL_VALID) << 8; + for (i =3D 0; i < num_lanes; i++) { + idx =3D scdc_err_cnt_buf_idx(i); + if (buf[idx + 1] & SCDC_CHANNEL_VALID) + counter[i] =3D buf[idx] | (buf[idx + 1] & ~SCDC_CHANNEL_VALID) << 8; else - counter[i / 2] =3D 0; - - buf[i] =3D 0; - buf[i + 1] =3D 0; + counter[i] =3D 0; } - buf[ARRAY_SIZE(buf) - 1] =3D 0; =20 - return drm_scdc_write(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(b= uf)); + memset(buf, 0, buf_sz); + + return drm_scdc_write(connector->ddc, SCDC_ERR_DET_0_L, buf, buf_sz); } EXPORT_SYMBOL(drm_scdc_read_error_counters); =20 @@ -385,6 +487,7 @@ int drm_scdc_read_state(struct drm_connector *connector= , struct drm_scdc_state * u8 upd_flags[2] =3D {}; struct i2c_adapter *ddc; struct drm_scdc *scdc; + int num_lanes; int ret; u8 val; =20 @@ -406,6 +509,19 @@ int drm_scdc_read_state(struct drm_connector *connecto= r, struct drm_scdc_state * =20 state->scrambling_detected =3D drm_scdc_get_scrambling_status(connector); =20 + ret =3D drm_scdc_readb(ddc, SCDC_CONFIG_1, &val); + if (ret) + return ret; + + state->rate =3D FIELD_GET(SCDC_FRL_RATE, val); + num_lanes =3D drm_scdc_num_frl_lanes(state->rate); + if (num_lanes < 0) + return num_lanes; + if (!num_lanes) + num_lanes =3D 3; + + state->ffe_levels =3D FIELD_GET(SCDC_FFE_LEVELS, val); + ret =3D drm_scdc_read(ddc, SCDC_UPDATE_0, &upd_flags, sizeof(upd_flags)); if (ret) return ret; @@ -416,8 +532,15 @@ int drm_scdc_read_state(struct drm_connector *connecto= r, struct drm_scdc_state * return ret; } =20 + if (upd_flags[0] & SCDC_FLT_UPDATE) { + ret =3D drm_scdc_read_status1_2_flags(connector, &state->stf); + if (ret) + return ret; + } + if (upd_flags[0] & SCDC_CED_UPDATE) { - ret =3D drm_scdc_read_error_counters(connector, state->error_count); + ret =3D drm_scdc_read_error_counters(connector, state->error_count, + num_lanes); if (ret) return ret; } @@ -465,6 +588,8 @@ static int scdc_status_show(struct seq_file *m, void *d= ata) =20 scdc_print_flag(m, "Scrambling Enabled", st->scrambling_enabled); scdc_print_flag(m, "Scrambling Detected", st->scrambling_detected); + scdc_print_str(m, "FRL Rate", drm_scdc_frl_rate_str(st->rate)); + scdc_print_dec(m, "FFE Levels", st->ffe_levels); =20 if (st->tmds_bclk_x40) scdc_print_str(m, "TMDS Bit Clock Ratio", "1/40"); @@ -475,10 +600,17 @@ static int scdc_status_show(struct seq_file *m, void = *data) scdc_print_flag(m, "Channel 0 Locked", st->stf.ch0_locked); scdc_print_flag(m, "Channel 1 Locked", st->stf.ch1_locked); scdc_print_flag(m, "Channel 2 Locked", st->stf.ch2_locked); + if (drm_scdc_num_frl_lanes(st->rate) =3D=3D 4) + scdc_print_flag(m, "Lane 3 Locked", st->stf.ln3_locked); + + scdc_print_flag(m, "Sink Ready For Link Training", st->stf.flt_ready); + scdc_print_flag(m, "Sink Failed To Decode DSC", st->stf.dsc_fail); =20 scdc_print_dec(m, "Channel 0 Errors", st->error_count[0]); scdc_print_dec(m, "Channel 1 Errors", st->error_count[1]); scdc_print_dec(m, "Channel 2 Errors", st->error_count[2]); + if (drm_scdc_num_frl_lanes(st->rate) =3D=3D 4) + scdc_print_dec(m, "Lane 3 Errors", st->error_count[3]); =20 return 0; =20 diff --git a/include/drm/display/drm_scdc.h b/include/drm/display/drm_scdc.h index 3d58f37e8ed8..9e365a95828d 100644 --- a/include/drm/display/drm_scdc.h +++ b/include/drm/display/drm_scdc.h @@ -29,6 +29,7 @@ #define SCDC_SOURCE_VERSION 0x02 =20 #define SCDC_UPDATE_0 0x10 +#define SCDC_FLT_UPDATE (1 << 5) #define SCDC_READ_REQUEST_TEST (1 << 2) #define SCDC_CED_UPDATE (1 << 1) #define SCDC_STATUS_UPDATE (1 << 0) @@ -46,14 +47,24 @@ #define SCDC_CONFIG_0 0x30 #define SCDC_READ_REQUEST_ENABLE (1 << 0) =20 +#define SCDC_CONFIG_1 0x31 +#define SCDC_FRL_RATE 0x0f +#define SCDC_FFE_LEVELS 0xf0 + #define SCDC_STATUS_FLAGS_0 0x40 +#define SCDC_DSC_FAIL (1 << 7) +#define SCDC_FLT_READY (1 << 6) +#define SCDC_LN3_LOCK (1 << 4) #define SCDC_CH2_LOCK (1 << 3) #define SCDC_CH1_LOCK (1 << 2) #define SCDC_CH0_LOCK (1 << 1) -#define SCDC_CH_LOCK_MASK (SCDC_CH2_LOCK | SCDC_CH1_LOCK | SCDC_CH0_LOCK) +#define SCDC_CH_LOCK_MASK (SCDC_LN3_LOCK | SCDC_CH2_LOCK | SCDC_CH1_LOCK = | \ + SCDC_CH0_LOCK) #define SCDC_CLOCK_DETECT (1 << 0) =20 #define SCDC_STATUS_FLAGS_1 0x41 +#define SCDC_LN_EVEN_TRAIN_PTRN 0x0f +#define SCDC_LN_ODD_TRAIN_PTRN 0xf0 =20 #define SCDC_ERR_DET_0_L 0x50 #define SCDC_ERR_DET_0_H 0x51 @@ -65,6 +76,9 @@ =20 #define SCDC_ERR_DET_CHECKSUM 0x56 =20 +#define SCDC_ERR_DET_3_L 0x57 +#define SCDC_ERR_DET_3_H 0x58 + #define SCDC_TEST_CONFIG_0 0xc0 #define SCDC_TEST_READ_REQUEST (1 << 7) #define SCDC_TEST_READ_REQUEST_DELAY(x) ((x) & 0x7f) diff --git a/include/drm/display/drm_scdc_helper.h b/include/drm/display/dr= m_scdc_helper.h index 3b3a4e0e48ba..926acf282cd3 100644 --- a/include/drm/display/drm_scdc_helper.h +++ b/include/drm/display/drm_scdc_helper.h @@ -24,6 +24,7 @@ #ifndef DRM_SCDC_HELPER_H #define DRM_SCDC_HELPER_H =20 +#include #include =20 #include @@ -38,8 +39,65 @@ struct drm_scdc_status_flags { bool ch0_locked; bool ch1_locked; bool ch2_locked; + bool ln3_locked; + bool flt_ready; + bool dsc_fail; + + /* Status Register 1 */ + u8 ln0_training_pattern : 4; + u8 ln1_training_pattern : 4; + + /* Status Register 2 */ + u8 ln2_training_pattern : 4; + u8 ln3_training_pattern : 4; +}; + +enum drm_scdc_frl_rate { + SCDC_FRL_RATE_OFF =3D 0, + SCDC_FRL_RATE_3X3 =3D 1, + SCDC_FRL_RATE_6X3 =3D 2, + SCDC_FRL_RATE_6X4 =3D 3, + SCDC_FRL_RATE_8X4 =3D 4, + SCDC_FRL_RATE_10X4 =3D 5, + SCDC_FRL_RATE_12X4 =3D 6, + SCDC_FRL_RATE_RESV_7 =3D 7, + SCDC_FRL_RATE_RESV_8 =3D 8, + SCDC_FRL_RATE_RESV_9 =3D 9, + SCDC_FRL_RATE_RESV_10 =3D 10, + SCDC_FRL_RATE_RESV_11 =3D 11, + SCDC_FRL_RATE_RESV_12 =3D 12, + SCDC_FRL_RATE_RESV_13 =3D 13, + SCDC_FRL_RATE_RESV_14 =3D 14, + SCDC_FRL_RATE_RESV_15 =3D 15 }; =20 +/** + * drm_scdc_num_frl_lanes - get number of lanes for a given FRL rate + * @rate: one of &enum drm_scdc_frl_rate + * + * For a given @rate, return the number of lanes it uses. + * + * Returns: %-EINVAL if @rate is not a valid FRL rate, or the number of la= nes + * for a given &enum drm_scdc_frl_rate on success (including %0 for "off") + */ +static inline __pure int drm_scdc_num_frl_lanes(enum drm_scdc_frl_rate rat= e) +{ + switch (rate) { + case SCDC_FRL_RATE_OFF: + return 0; + case SCDC_FRL_RATE_3X3: + case SCDC_FRL_RATE_6X3: + return 3; + case SCDC_FRL_RATE_6X4: + case SCDC_FRL_RATE_8X4: + case SCDC_FRL_RATE_10X4: + case SCDC_FRL_RATE_12X4: + return 4; + default: + return -EINVAL; + } +} + struct drm_scdc_state { /** @stf: contents of the status flag registers */ struct drm_scdc_status_flags stf; @@ -52,8 +110,12 @@ struct drm_scdc_state { * clock period, false if it's 1/10th of the clock period. */ bool tmds_bclk_x40; - /** @error_count: character error counts for each channel */ - u16 error_count[3]; + /** @rate: FRL rate set by the source */ + enum drm_scdc_frl_rate rate : 4; + /** @ffe_levels: The FFE levels for @rate set by the source */ + u8 ffe_levels : 4; + /** @error_count: character error counts for each channel/link */ + u16 error_count[4]; }; =20 int drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, @@ -104,9 +166,12 @@ bool drm_scdc_set_high_tmds_clock_ratio(struct drm_con= nector *connector, bool se =20 int drm_scdc_read_status0_flags(struct drm_connector *connector, struct drm_scdc_status_flags *flags); +int drm_scdc_read_status1_2_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags); int drm_scdc_read_state(struct drm_connector *connector, struct drm_scdc_state *state); -int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[3]); +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 coun= ter[4], + unsigned int num_lanes); void drm_scdc_debugfs_init(struct drm_connector *connector, struct dentry = *root); =20 #endif --=20 2.54.0