Re: [PATCH v1 2/3] i2c: qcom-geni: Add bus recovery support for FIFO mode

[Jyothi Kumar Seerapu <jyothi.seerapu@oss.qualcomm.com>]

On 8/26/2026 3:21 PM, Aniket Randive wrote:
> I2C transfers in FIFO mode can fail with -EPROTO, -ETIMEDOUT or
> -EAGAIN when a target holds SDA low, leaving the bus stuck and
> preventing subsequent transactions.
> 
> Add bus recovery support using the I2C_BUS_CLEAR and I2C_STOP_ON_BUS
> hardware opcodes to restore the bus to an idle state. Check the SDA
> line state through SE_GENI_IOS.RX_DATA_IN and skip recovery when the
> bus is already free. Trigger recovery automatically from
> geni_i2c_xfer() on -EPROTO, -ETIMEDOUT and -EAGAIN (arbitration-lost)
> errors, and register the recovery callback through i2c_bus_recovery_info
> to allow recovery via i2c_recover_bus().
> 
> This adds bus recovery support for FIFO mode only.
> 
> Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
> ---
>   drivers/i2c/busses/i2c-qcom-geni.c | 109 +++++++++++++++++++++++++++++++++++++
>   1 file changed, 109 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 658636c1ee0e..9fa1a8ac400c 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -138,6 +138,7 @@ struct geni_i2c_dev {
>   	u32 num_msgs;
>   	struct geni_i2c_gpi_multi_desc_xfer i2c_multi_desc_config;
>   	const struct geni_i2c_desc *dev_data;
> +	struct i2c_bus_recovery_info rinfo;
>   };
>   
>   struct geni_i2c_err_log {
> @@ -956,6 +957,90 @@ static int geni_i2c_fifo_xfer(struct geni_i2c_dev *gi2c,
>   	return num;
>   }
>   
> +static int geni_i2c_fifo_bus_cmd(struct geni_i2c_dev *gi2c, u32 cmd)
> +{
> +	unsigned long time_left;
> +	unsigned long flags;
> +
> +	/*
> +	 * Clear cur so the IRQ handler does not attempt FIFO watermark
> +	 * filling or draining while the recovery opcode is in flight.
> +	 * cur and err are shared with geni_i2c_irq(), which reads cur and
> +	 * writes err under gi2c->lock, so take the lock around this reset.
> +	 */
> +	spin_lock_irqsave(&gi2c->lock, flags);
> +	gi2c->cur = NULL;
> +	gi2c->err = 0;
> +	spin_unlock_irqrestore(&gi2c->lock, flags);
> +	geni_se_select_mode(&gi2c->se, GENI_SE_FIFO);
> +	reinit_completion(&gi2c->done);
> +
> +	geni_se_setup_m_cmd(&gi2c->se, cmd, 0);
> +	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> +	if (!time_left) {
> +		dev_err(gi2c->se.dev, "timeout waiting for bus cmd %u\n", cmd);
> +		gi2c->abort_done = false;
> +		geni_se_abort_m_cmd(&gi2c->se);
> +		time_left = ABORT_TIMEOUT;
> +		do {
> +			time_left = wait_for_completion_timeout(&gi2c->done, time_left);
> +		} while (!gi2c->abort_done && time_left);
> +
> +		if (!time_left)
> +			dev_err(gi2c->se.dev, "abort timed out for bus cmd %u\n", cmd);
> +
> +		return -ETIMEDOUT;
> +	}
> +
> +	/*
> +	 * ARB_LOST and BUS_PROTO interrupts may be reported while the bus
> +	 * transitions from stuck to idle during the recovery sequence.
> +	 * The opcode completed successfully so treat these as success.
> +	 */
> +	if (gi2c->err == -EAGAIN || gi2c->err == -EPROTO)
> +		return 0;
> +
> +	return gi2c->err;
> +}
> +
> +static int geni_i2c_recover_bus(struct i2c_adapter *adap)
> +{
> +	struct geni_i2c_dev *gi2c = i2c_get_adapdata(adap);
> +	int ret;
> +
> +	ret = pm_runtime_get_sync(gi2c->se.dev);
> +	if (ret < 0) {
> +		dev_err(gi2c->se.dev, "bus recovery failed, error turning SE resources:%d\n", ret);
> +		pm_runtime_put_noidle(gi2c->se.dev);
> +		return ret;
> +	}
> +
> +	/* SDA is high means bus is free */
What about SCL line ?> +	if (readl_relaxed(gi2c->se.base + SE_GENI_IOS) 
& RX_DATA_IN) {
> +		pm_runtime_put_autosuspend(gi2c->se.dev);
> +		return 0;
> +	}
> +
> +	ret = geni_i2c_fifo_bus_cmd(gi2c, I2C_BUS_CLEAR);
> +	if (!ret)
> +		ret = geni_i2c_fifo_bus_cmd(gi2c, I2C_STOP_ON_BUS);
> +
> +	/*
> +	 * Recovery succeeds only once the slave releases SDA, so the bus
> +	 * state is the authority: RX_DATA_IN high means the bus is free,
> +	 * while a clean opcode status with SDA still low is a failed
> +	 * recovery.
> +	 */
> +	if (readl_relaxed(gi2c->se.base + SE_GENI_IOS) & RX_DATA_IN)
> +		ret = 0;
> +	else if (!ret)
> +		ret = -EBUSY;
> +
> +	pm_runtime_put_autosuspend(gi2c->se.dev);
> +
> +	return ret;
> +}
> +
>   static int geni_i2c_xfer(struct i2c_adapter *adap,
>   			 struct i2c_msg msgs[],
>   			 int num)
> @@ -981,6 +1066,25 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
>   	else
>   		ret = geni_i2c_fifo_xfer(gi2c, msgs, num);
>   
> +	if (!gi2c->gpi_mode &&
> +	    (ret == -EPROTO || ret == -ETIMEDOUT || ret == -EAGAIN)) {
> +		/*
> +		 * Only attempt recovery if SDA is stuck low. -EPROTO and
> +		 * -ETIMEDOUT indicate bus errors where the target may be
> +		 * holding SDA low. ARB_LOST (-EAGAIN) on a single-controller
> +		 * bus indicates a stuck target, not a real arbitration loss.
> +		 * GPI DMA mode extends this trigger separately.
> +		 */
> +		if (!(readl_relaxed(gi2c->se.base + SE_GENI_IOS) & RX_DATA_IN)) {
> +			int recovery_ret = i2c_recover_bus(adap);
> +
> +			if (recovery_ret)
> +				dev_err(gi2c->se.dev,
> +					"bus recovery failed: %d (xfer error: %d)\n",
> +					recovery_ret, ret);
> +		}
Can we move this to a helper function like "geni_i2c_need_bus_recovery" 
?> +	}
> +
>   	pm_runtime_put_autosuspend(gi2c->se.dev);
>   	gi2c->cur = NULL;
>   	gi2c->err = 0;
> @@ -1188,6 +1292,11 @@ static int geni_i2c_probe(struct platform_device *pdev)
>   	if (ret < 0)
>   		return ret;
>   
> +	if (!gi2c->gpi_mode) {
> +		gi2c->rinfo.recover_bus = geni_i2c_recover_bus;
> +		gi2c->adap.bus_recovery_info = &gi2c->rinfo;
> +	}
In geni_i2c_xfer(), geni_i2c_recover_bus() is invoked directly, then why 
do we need this ?> +
>   	ret = i2c_add_adapter(&gi2c->adap);
>   	if (ret)
>   		return dev_err_probe(dev, ret, "Error adding i2c adapter\n");
>