Commit fa070ee6 authored Oct 14, 2013 by Lukasz Dorau Committed by Tejun Heo Oct 15, 2013

libahci: fix turning on LEDs in ahci_start_port()



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.

tj: updated comment

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent f13e2201

drivers/ata/libahci.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -778,8 +778,16 @@ static void ahci_start_port(struct ata_port *ap)
		rc = ap->ops->transmit_led_message(ap,
		emp->led_state,
		4);
		/*
		* If busy, give a breather but do not
		* release EH ownership by using msleep()
		* instead of ata_msleep(). EM Transmit
		* bit is busy for the whole host and
		* releasing ownership will cause other
		* ports to fail the same way.
		*/
		if (rc == -EBUSY)
		ata_msleep(ap, 1);
		msleep(1);
		else
		break;
		}

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