Currently interrupt storm will occur from i2c-i801 after first transaction if SMB_ALERT signal is enabled and ever asserted. It is enough if the signal is asserted once even before the driver is loaded and does not recover because that interrupt is not acknowledged. This fix aims to fix it by two ways: - Add acknowledging for the SMB_ALERT interrupt status - Disable the SMB_ALERT interrupt on platforms where possible since the driver currently does not make use for it Acknowledging resets the SMB_ALERT interrupt status on all platforms and also should help to avoid interrupt storm on older platforms where the SMB_ALERT interrupt disabling is not available. For simplicity this fix reuses the host notify feature for disabling and restoring original register value. Link: https://bugzilla.kernel.org/show_bug.cgi?id=177311 Reported-by: ck+kernelbugzilla@xxxxxxxxxxx Reported-by: stephane.poignant@xxxxxxxxxxxxxx Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx> --- v2: More verbose commenting around interrupt acknowledging, reporting and SMB_ALERT disabling. Fix typo in commit log and split the first sentence. v1: Hi Conrad and Stephane. This patch is otherwise the same than the one I had in bugzilla but this adds also acknowledging for the SMB_ALERT interrupt. There is short time window during driver load and unload where interrupt storm will still occur if signal was asserted. Also interrupt disabling is possible only on ICH3 and later so interrupt acknowledging should also help those old platforms. --- drivers/i2c/busses/i2c-i801.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c index 115660dce722..cf6cf419c760 100644 --- a/drivers/i2c/busses/i2c-i801.c +++ b/drivers/i2c/busses/i2c-i801.c @@ -190,6 +190,7 @@ #define SMBSLVSTS_HST_NTFY_STS BIT(0) /* Host Notify Command register bits */ +#define SMBSLVCMD_SMBALERT_DISABLE BIT(2) #define SMBSLVCMD_HST_NTFY_INTREN BIT(0) #define STATUS_ERROR_FLAGS (SMBHSTSTS_FAILED | SMBHSTSTS_BUS_ERR | \ @@ -639,12 +640,20 @@ static irqreturn_t i801_isr(int irq, void *dev_id) i801_isr_byte_done(priv); /* - * Clear irq sources and report transaction result. + * Clear remaining irq sources: Completion of last command, errors + * and the SMB_ALERT signal. SMB_ALERT status is set after signal + * assertion also when the interrupt from it is blocked on platforms + * where disabling is possible so clear it always when status is set. + */ + status &= SMBHSTSTS_INTR | STATUS_ERROR_FLAGS | SMBHSTSTS_SMBALERT_STS; + if (status) + outb_p(status, SMBHSTSTS(priv)); + status &= ~SMBHSTSTS_SMBALERT_STS; /* SMB_ALERT not reported */ + /* + * Report transaction result. * ->status must be cleared before the next transaction is started. */ - status &= SMBHSTSTS_INTR | STATUS_ERROR_FLAGS; if (status) { - outb_p(status, SMBHSTSTS(priv)); priv->status = status; complete(&priv->done); } @@ -972,9 +981,12 @@ static void i801_enable_host_notify(struct i2c_adapter *adapter) if (!(priv->features & FEATURE_HOST_NOTIFY)) return; - if (!(SMBSLVCMD_HST_NTFY_INTREN & priv->original_slvcmd)) - outb_p(SMBSLVCMD_HST_NTFY_INTREN | priv->original_slvcmd, - SMBSLVCMD(priv)); + /* + * Enable host notify interrupt and block the generation of interrupt + * from the SMB_ALERT signal. + */ + outb_p(SMBSLVCMD_HST_NTFY_INTREN | SMBSLVCMD_SMBALERT_DISABLE | + priv->original_slvcmd, SMBSLVCMD(priv)); /* clear Host Notify bit to allow a new notification */ outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv)); -- 2.33.0
