Re: [PATCH v3] i2c: i801: Don't clear status flags twice in interrupt mode

Jean Delvare
2021-12-09T13:10:07Z

On Sat, 04 Dec 2021 21:04:40 +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 handle polling mode by using the
> SMBus unlocking write to also clear the status flags if still set.
> To be precise: One could still argue that the status flags are
> cleared twice in interrupt mode, but it comes for free.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> v2:
> - clear status flags also in i801_wait_byte_done()
> - remove outdated comment at i801_check_post()
> v3:
> - merge unlocking SMBus and clearing status flags
> - avoid the complexity added with v2
> ---
> drivers/i2c/busses/i2c-i801.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index 930c6edbe..128a25de7 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -372,11 +372,6 @@ static int i801_check_pre(struct i801_priv *priv)
> return 0;
> }
>
> -/*
> - * Convert the status register to an error code, and clear it.
> - * Note that status only contains the bits we want to clear, not the
> - * actual register value.
> - */
> static int i801_check_post(struct i801_priv *priv, int status)
> {
> int result = 0;
> @@ -401,7 +396,6 @@ static int i801_check_post(struct i801_priv *priv, int status)
> !(status & SMBHSTSTS_FAILED))
> dev_err(&priv->pci_dev->dev,
> "Failed terminating the transaction\n");
> - outb_p(STATUS_FLAGS, SMBHSTSTS(priv));
> return -ETIMEDOUT;
> }
>
> @@ -440,9 +434,6 @@ 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;
> }
>
> @@ -939,8 +930,11 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
> }
>
> out:
> - /* Unlock the SMBus device for use by BIOS/ACPI */
> - outb_p(SMBHSTSTS_INUSE_STS, SMBHSTSTS(priv));
> + /*
> + * Unlock the SMBus device for use by BIOS/ACPI,
> + * and clear status flags if not done already.
> + */
> + outb_p(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv));
>
> pm_runtime_mark_last_busy(&priv->pci_dev->dev);
> pm_runtime_put_autosuspend(&priv->pci_dev->dev);

Looks good to me.

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jean Delvare <jdelvare@suse.de>

--
Jean Delvare
SUSE L3 Support