[PATCH] ACPI / EC: Restart transaction even when the IBF flag set

[Luis Henriques]

Alex Hung <alex.hung at canonical.com> writes:

> From: Lan Tianyu <tianyu.lan at intel.com>
>
> The EC driver works abnormally with IBF flag always set.
> IBF means "The host has written a byte of data to the command
> or data port, but the embedded controller has not yet read it".
> If IBF is set in the EC status and not cleared, this will cause
> all subsequent EC requests to fail with a timeout error.
>
> Change the EC driver so that it doesn't refuse to restart a
> transaction if IBF is set in the status.  Also increase the
> number of transaction restarts to 5, as it turns out that 2
> is not sufficient in some cases.
>
> This bug happens on several different machines (Asus V1S,
> Dell Latitude E6530, Samsung R719, Acer Aspire 5930G,
> Sony Vaio SR19VN and others).
>
> [rjw: Changelog]
> References: https://bugzilla.kernel.org/show_bug.cgi?id=14733
> References: https://bugzilla.kernel.org/show_bug.cgi?id=15560
> References: https://bugzilla.kernel.org/show_bug.cgi?id=15946
> References: https://bugzilla.kernel.org/show_bug.cgi?id=42945
> References: https://bugzilla.kernel.org/show_bug.cgi?id=48221
> Signed-off-by: Lan Tianyu <tianyu.lan at intel.com>
> Cc: All <stable at vger.kernel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> (cherry picked from commit 28fe5c825f8e15744d04c7c1b8df197950923ecd)

Besides the fact that this commit doesn't contain the buglink (its
only in the cover email), it is already present in both Q and R
kernels.

Cheers,
-- 
Luis

>
> Signed-off-by: Alex Hung <alex.hung at canonical.com>
> ---
>  drivers/acpi/ec.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 354007d..a563e11 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -223,7 +223,7 @@ static int ec_check_sci_sync(struct acpi_ec *ec, u8 state)
>  static int ec_poll(struct acpi_ec *ec)
>  {
>  	unsigned long flags;
> -	int repeat = 2; /* number of command restarts */
> +	int repeat = 5; /* number of command restarts */
>  	while (repeat--) {
>  		unsigned long delay = jiffies +
>  			msecs_to_jiffies(ec_delay);
> @@ -241,8 +241,6 @@ static int ec_poll(struct acpi_ec *ec)
>  			}
>  			advance_transaction(ec, acpi_ec_read_status(ec));
>  		} while (time_before(jiffies, delay));
> -		if (acpi_ec_read_status(ec) & ACPI_EC_FLAG_IBF)
> -			break;
>  		pr_debug(PREFIX "controller reset, restart transaction\n");
>  		spin_lock_irqsave(&ec->lock, flags);
>  		start_transaction(ec);
> -- 
> 1.7.9.5