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A static timeout causes unnecessary delays on error paths for short messages, and may be insufficient for very long transfers. Add i2c_update_timeout() to i2c-core which computes a transfer-specific timeout and stores it directly in the standard adap->timeout field. The formula accounts for 9 bits per byte (8 data + 1 ACK) at the configured bus frequency. The caller supplies a safety multiplier and a minimum floor so that each driver retains full control over its timing policy without those values becoming public API. Storing the result in adap->timeout makes it visible to all consumers of that field, including the arbitration-loss retry loop in __i2c_transfer(). Signed-off-by: Aniket Randive --- drivers/i2c/i2c-core-base.c | 24 ++++++++++++++++++++++++ include/linux/i2c.h | 3 +++ 2 files changed, 27 insertions(+) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 3ec04787a737..3280652e20d8 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include #include @@ -2000,6 +2001,29 @@ void i2c_parse_fw_timings(struct device *dev, struct= i2c_timings *t, bool use_de } EXPORT_SYMBOL_GPL(i2c_parse_fw_timings); =20 +/** + * i2c_update_timeout - compute and set a dynamic transfer timeout on an a= dapter + * @adap: the i2c_adapter whose timeout field will be updated + * @bus_freq_hz: I2C bus clock frequency in Hz + * @len: transfer length in bytes + * @safety_coeff: multiplier applied over the theoretical wire time + * @min_usec: minimum timeout floor in microseconds + * + * Computes a transfer-specific timeout from the message length and bus + * frequency, applies a safety multiplier and a minimum floor, then stores + * the result in adap->timeout (in jiffies). The caller supplies the poli= cy + * constants so they remain internal to the driver. + */ +void i2c_update_timeout(struct i2c_adapter *adap, u32 bus_freq_hz, + size_t len, unsigned int safety_coeff, + unsigned int min_usec) +{ + u64 bit_usec =3D mul_u64_u32_div(len * 9, USEC_PER_SEC, bus_freq_hz); + + adap->timeout =3D usecs_to_jiffies(bit_usec * safety_coeff + min_usec); +} +EXPORT_SYMBOL_GPL(i2c_update_timeout); + /* -----------------------------------------------------------------------= -- */ =20 int i2c_for_each_dev(void *data, int (*fn)(struct device *dev, void *data)) diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 14ab4d3055af..b52974eb7e58 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -912,6 +912,9 @@ void i2c_put_adapter(struct i2c_adapter *adap); unsigned int i2c_adapter_depth(struct i2c_adapter *adapter); =20 void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool = use_defaults); +void i2c_update_timeout(struct i2c_adapter *adap, u32 bus_freq_hz, + size_t len, unsigned int safety_coeff, + unsigned int min_usec); 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Mon, 20 Jul 2026 04:41:35 -0700 (PDT) X-Received: by 2002:a05:6a00:1a94:b0:847:770f:da4c with SMTP id d2e1a72fcca58-84c2930540cmr13432653b3a.16.1784547694597; Mon, 20 Jul 2026 04:41:34 -0700 (PDT) Received: from hu-arandive-hyd.qualcomm.com ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84c2adfdfe9sm5450701b3a.27.2026.07.20.04.41.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 04:41:34 -0700 (PDT) From: Aniket Randive Date: Mon, 20 Jul 2026 17:11:20 +0530 Subject: [PATCH v6 2/2] i2c: qcom-geni: Add dynamic transfer timeout based on transfer length and frequency 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: <20260720-master-v6-2-671261b05c61@oss.qualcomm.com> References: <20260720-master-v6-0-671261b05c61@oss.qualcomm.com> In-Reply-To: <20260720-master-v6-0-671261b05c61@oss.qualcomm.com> To: Andi Shyti , Mukesh Kumar Savaliya , Viken Dadhaniya Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Aniket Randive X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; 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Use i2c_update_timeout() from i2c-core to compute the timeout dynamically from the maximum message length across the transfer batch and the bus frequency, then read adap->timeout at each wait site. The timeout is updated once per transfer batch in geni_i2c_xfer() so all internal paths (FIFO rx/tx and both GPI modes) use a consistent value. A 10x safety margin over the theoretical wire time is applied, with a 300ms floor to account for I2C clock stretching and other situations where a slave may keep SCL asserted for an extended period, including faulty devices holding the bus. Both constants remain private to this driver. Signed-off-by: Aniket Randive --- drivers/i2c/busses/i2c-qcom-geni.c | 37 +++++++++++++++++++++++++++++-----= --- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qc= om-geni.c index 96dbf04138be..d6fab3aa8468 100644 --- a/drivers/i2c/busses/i2c-qcom-geni.c +++ b/drivers/i2c/busses/i2c-qcom-geni.c @@ -74,9 +74,14 @@ enum geni_i2c_err_code { #define PACKING_BYTES_PW 4 =20 #define ABORT_TIMEOUT HZ -#define XFER_TIMEOUT HZ #define RST_TIMEOUT HZ =20 +/* 9 bits per byte (8 data + 1 ACK), 10x safety margin */ +#define I2C_TIMEOUT_SAFETY_COEFFICIENT 10 + +/* 300ms floor: budget for clock stretching; slave may hold SCL low indefi= nitely */ +#define I2C_TIMEOUT_MIN_USEC 300000 + struct geni_i2c_desc { bool no_dma_support; unsigned int tx_fifo_depth; @@ -471,7 +476,9 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2= c, struct i2c_msg *msg, } =20 cur =3D gi2c->cur; - time_left =3D wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, len, + I2C_TIMEOUT_SAFETY_COEFFICIENT, I2C_TIMEOUT_MIN_USEC); + time_left =3D wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeout= ); if (!time_left) geni_i2c_abort_xfer(gi2c); =20 @@ -513,7 +520,9 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2= c, struct i2c_msg *msg, writel_relaxed(1, se->base + SE_GENI_TX_WATERMARK_REG); =20 cur =3D gi2c->cur; - time_left =3D wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, len, + I2C_TIMEOUT_SAFETY_COEFFICIENT, I2C_TIMEOUT_MIN_USEC); + time_left =3D wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeout= ); if (!time_left) geni_i2c_abort_xfer(gi2c); =20 @@ -591,7 +600,7 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i= 2c_dev *gi2c, struct i2c_ * geni_i2c_gpi_multi_xfer_timeout_handler() - Handles multi message trans= fer timeout * @dev: Pointer to the corresponding dev node * @multi_xfer: Pointer to the geni_i2c_gpi_multi_desc_xfer - * @transfer_timeout_msecs: Timeout value in milliseconds + * @transfer_timeout_msecs: Per-message completion timeout in jiffies * @transfer_comp: Completion object of the transfer * * This function waits for the completion of each processed transfer messa= ges @@ -601,7 +610,7 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i= 2c_dev *gi2c, struct i2c_ */ static int geni_i2c_gpi_multi_xfer_timeout_handler(struct device *dev, struct geni_i2c_gpi_multi_desc_xfer *multi_xfer, - u32 transfer_timeout_msecs, + unsigned long timeout_jiffies, struct completion *transfer_comp) { int i; @@ -612,7 +621,7 @@ static int geni_i2c_gpi_multi_xfer_timeout_handler(stru= ct device *dev, =20 if (multi_xfer->msg_idx_cnt !=3D multi_xfer->irq_cnt) { time_left =3D wait_for_completion_timeout(transfer_comp, - transfer_timeout_msecs); + timeout_jiffies); if (!time_left) { dev_err(dev, "%s: Transfer timeout\n", __func__); return -ETIMEDOUT; @@ -736,8 +745,17 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, str= uct i2c_msg msgs[], dma_async_issue_pending(gi2c->tx_c); =20 if ((msg_idx =3D=3D (gi2c->num_msgs - 1)) || flags & DMA_PREP_INTERRUPT)= { + size_t max_len =3D 0; + int j; + + for (j =3D 0; j < gi2c->num_msgs; j++) + max_len =3D max_t(size_t, max_len, msgs[j].len); + i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, max_len, + I2C_TIMEOUT_SAFETY_COEFFICIENT, + I2C_TIMEOUT_MIN_USEC); ret =3D geni_i2c_gpi_multi_xfer_timeout_handler(gi2c->se.dev, gi2c_gpi_= xfer, - XFER_TIMEOUT, &gi2c->done); + gi2c->adap.timeout, + &gi2c->done); if (ret) { dev_err(gi2c->se.dev, "I2C multi write msg transfer timeout: %d\n", @@ -852,7 +870,10 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c= , struct i2c_msg msgs[], i =20 if (!gi2c->is_tx_multi_desc_xfer) { dma_async_issue_pending(gi2c->tx_c); - time_left =3D wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, msgs[i].len, + I2C_TIMEOUT_SAFETY_COEFFICIENT, + I2C_TIMEOUT_MIN_USEC); + time_left =3D wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeo= ut); if (!time_left) { dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__); gi2c->err =3D -ETIMEDOUT; --=20 2.34.1