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In these > cases, i2c_transfer() returns -EREMOTEIO. > > The CCG4 is EOL, and Infineon no longer supports firmware updates, so > a software workaround is necessary. > > Attempt the read up to CCG_READ_MAX_RETRIES (4) times in total when > -EREMOTEIO is returned, sleeping ~1 ms via fsleep() between attempts. > This allows recovery from transient I2C failures without affecting > other error paths. > > The sleep is safe because ccg_read() is called both from process > context and from ccg_irq_handler(), which runs in threaded IRQ > context (registered via request_threaded_irq() with a NULL hard-IRQ > handler), so sleeping is allowed in both cases. > > Fixes: 247c554a14aa ("usb: typec: ucsi: add support for Cypress CCGx") > Cc: stable@vger.kernel.org > Signed-off-by: Wayne Chang > --- > v1 -> v2: Per Heikki's review: > - Fix off-by-one: CCG_READ_MAX_RETRIES was 3 but the loop ran 4 times > (retry_count <= CCG_READ_MAX_RETRIES). Changed the macro to 4 (the > actual total attempt count) and the loop condition to > retry_count < CCG_READ_MAX_RETRIES, so the name and the loop bound > now agree. Adjusted the "skip the sleep on the last attempt" check > to retry_count == CCG_READ_MAX_RETRIES - 1 to match. > - Use fsleep(1000) instead of usleep_range(1000, 2000). > - Reworded the commit message to say "up to CCG_READ_MAX_RETRIES (4) > times in total" instead of the ambiguous "up to three times (four > attempts total)" that prompted the off-by-one question. > > drivers/usb/typec/ucsi/ucsi_ccg.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/typec/ucsi/ucsi_ccg.c b/drivers/usb/typec/ucsi/ucsi_ccg.c > index 91c2958a708c..4b6c53d2a998 100644 > --- a/drivers/usb/typec/ucsi/ucsi_ccg.c > +++ b/drivers/usb/typec/ucsi/ucsi_ccg.c > @@ -135,6 +135,8 @@ struct version_format { > #define NVIDIA_FTB_DP_OFFSET (2) > #define NVIDIA_FTB_DBG_OFFSET (3) > > +#define CCG_READ_MAX_RETRIES 4 > + > struct version_info { > struct version_format base; > struct version_format app; > @@ -255,6 +257,7 @@ static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len) > }; > u32 rlen, rem_len = len, max_read_len = len; > int status; > + int retry_count; > > /* check any max_read_len limitation on i2c adapter */ > if (quirks && quirks->max_read_len) > @@ -266,7 +269,17 @@ static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len) > rlen = min_t(u16, rem_len, max_read_len); > msgs[1].len = rlen; > put_unaligned_le16(rab, buf); > - status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); > + > + for (retry_count = 0; retry_count < CCG_READ_MAX_RETRIES; retry_count++) { > + status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); > + > + /* Only retry on -EREMOTEIO, and not after the last attempt */ > + if (status != -EREMOTEIO || retry_count == CCG_READ_MAX_RETRIES - 1) > + break; > + > + fsleep(1000); > + } > + > if (status < 0) { > dev_err(uc->dev, "i2c_transfer failed %d\n", status); > pm_runtime_put_sync(uc->dev); I was wondering if we could avoid the extra check inside the loop for 'CCG_READ_MAX_RETRIES - 1' but this does avoid an addition sleep. So ... Reviewed-by: Jon Hunter Tested-by: Jon Hunter Thanks! Jon -- nvpublic