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SubjectRe: [PATCH] libahci: fix turning on LEDs in ahci_start_port()
On Mon, Oct 14, 2013 at 02:58:19PM +0200, Lukasz Dorau wrote:
> If EM Transmit bit is busy during init ata_msleep() is called.
> It is wrong - msleep() should be used instead of ata_msleep(),
> because if EM Transmit bit is busy for one port, it will be busy
> for all other ports too, so using ata_msleep() causes wasting
> tries for another ports.
>
> The most common scenario looks like that now
> (six ports try to transmit a LED meaasege):
> - port #0 tries for the 1st time and succeeds
> - ports #1-5 try for the 1st time and sleeps
> - port #1 tries for the 2nd time and succeeds
> - ports #2-5 try for the 2nd time and sleeps
> - port #2 tries for the 3rd time and succeeds
> - ports #3-5 try for the 3rd time and sleeps
> - port #3 tries for the 4th time and succeeds
> - ports #4-5 try for the 4th time and sleeps
> - port #4 tries for the 5th time and succeeds
> - port #5 tries for the 5th time and sleeps
> At this moment port #5 wasted all its five tries and failed to initialize.
> Because there are only 5 (EM_MAX_RETRY) tries available usually only five ports
> succeed to initialize. The sixth port and next ones usually will fail.
>
> If msleep() is used instead of ata_msleep() the first port succeeds to initialize
> in the first try and next ones usually succeed to initialize in the second try.

Ah, interesting.

> Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>
> ---
> drivers/ata/libahci.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index acfd0f7..cf38692 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -779,7 +779,7 @@ static void ahci_start_port(struct ata_port *ap)
> emp->led_state,
> 4);
> if (rc == -EBUSY)
> - ata_msleep(ap, 1);
> + msleep(1);

This is so unobvious. Can you please add a comment explaining what's
going on?

Thanks.

--
tejun


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