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

Heiner Kallweit
2021-12-04T20:04:52Z

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- remove outdated comment at i801_check_post()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);
--
2.34.1