On 03.12.2021 11:41, Jean Delvare wrote: > Hi Heiner, > > On Thu, 02 Dec 2021 10:57:43 +0100, Heiner Kallweit wrote: >> In interrupt mode we clear the status flags twice, in the interrupt >> handler and in i801_check_post(). Remove clearing the status flags >> from i801_check_post() and let i801_wait_intr() clear them in >> polling mode. Another benefit is that now only checks for error >> conditions are left in i801_check_post(), thus better matching the >> function name. >> >> Note: There's a comment in i801_check_post() that i801_wait_intr() >> clears the error status bits. Actually this hasn't been true until >> this change. > > While reviewing this, I have noticed other comments which seem outdated: > > * In i801_isr(), "->status must be cleared before the next transaction > is started." We no longer do this since > 1de93d5d521717cbb77cc9796a4df141d800d608, and things are working > well, so clearly this is no longer necessary and the comment could be > removed. > * The comment before i801_check_post() is obsoleted by your > proposed change. > >> >> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx> >> --- >> drivers/i2c/busses/i2c-i801.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c >> index 7446bed78..82553e0cb 100644 >> --- a/drivers/i2c/busses/i2c-i801.c >> +++ b/drivers/i2c/busses/i2c-i801.c >> @@ -438,9 +438,6 @@ static int i801_check_post(struct i801_priv *priv, int status) >> dev_dbg(&priv->pci_dev->dev, "Lost arbitration\n"); >> } >> >> - /* Clear status flags except BYTE_DONE, to be cleared by caller */ >> - outb_p(status, SMBHSTSTS(priv)); >> - >> return result; >> } >> >> @@ -455,8 +452,10 @@ static int i801_wait_intr(struct i801_priv *priv) >> status = inb_p(SMBHSTSTS(priv)); >> busy = status & SMBHSTSTS_HOST_BUSY; >> status &= STATUS_ERROR_FLAGS | SMBHSTSTS_INTR; >> - if (!busy && status) >> + if (!busy && status) { >> + outb_p(status, SMBHSTSTS(priv)); >> return status; >> + } >> } while (time_is_after_eq_jiffies(timeout)); >> >> return -ETIMEDOUT; > > I like the idea to make things consistent between the interrupt and > poll modes, however I'm afraid there's one code path not covered by > your patch. If i801_wait_byte_done() returns an error flag in > i801_block_transaction_byte_by_byte(), we jump directly to > i801_check_post() without calling i801_wait_intr(). In that case, the > error flags are not cleared, right? Doesn't look good. > Indeed, good point. I have an idea, I'll propose a patch that we can use as discussion basis. > Makes me wonder if we shouldn't actually let i801_check_post() clear > the flags and remove that piece of code everywhere else? Or is there a > reason why it has to be done earlier in i801_isr(), that I do not > remember? > I'd like to achieve that check_pre/post() only check and handle error conditions. Both functions shouldn't be involved in the normal flow. > I'm also wondering if there's actually any reason to clear the flags at > all at the end of the transaction, considering that we'll be doing it > again at the beginning of the next transaction anyway to be on the safe > side. > Clearing flags in check_pre() should just be a last resort (IMO). The regular flow should leave the flags in a clean state.