Re: [PATCH v1 2/3] i2c: qcom-geni: Add bus recovery support for FIFO mode
From: Aniket RANDIVE
Date: Fri Oct 09 2026 - 02:58:40 EST
On 9/3/2026 9:47 PM, Jyothi Kumar Seerapu wrote:
On 8/26/2026 3:21 PM, Aniket Randive wrote:
I2C transfers in FIFO mode can fail with -EPROTO, -ETIMEDOUT orWhat about SCL line ?> + if (readl_relaxed(gi2c->se.base + SE_GENI_IOS) & RX_DATA_IN) {
-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@xxxxxxxxxxxxxxxx>
---
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 */
Yes. I will add a check for SCL Line as well.
+ pm_runtime_put_autosuspend(gi2c->se.dev);Can we move this to a helper function like "geni_i2c_need_bus_recovery" ?> + }
+ 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);
+ }
Yes. I will add helper function here.
+In geni_i2c_xfer(), geni_i2c_recover_bus() is invoked directly, then why do we need this ?> +
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;
+ }
It exposes recovery through the standard I²C core API for any future caller, rather than relying on a driver-private direct call. The registration tells the I²C core that “this adapter supports recovery. call geni_i2c_recover_bus() for it.”
ret = i2c_add_adapter(&gi2c->adap);
if (ret)
return dev_err_probe(dev, ret, "Error adding i2c adapter\n");