Re: [RFC PATCH] AHCI: speed up resume

[Jeff Garzik]

Zhang Rui wrote:
> On Fri, 2008-07-04 at 10:48 +0800, Tejun Heo wrote:
> > Hello, Zhang.
> >
> > Zhang Rui wrote:
> > > During S3 resume, AHCI driver sleeps 1 second to wait for the HBA
> > reset
> > > to finish. This is luxurious, :)
> > >
> > > According to the AHCI 1.2 spec, We should poll the HOST_CTL
> > register,
> > > and return error if the host reset is not finished within 1 second.
> > >
> > > Test results show that the HBA reset can be done quickly(in usecs).
> > > And this patch may save nearly 1 second during resume.
> > >
> > > Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
> > > --
> > >  drivers/ata/ahci.c |   17 ++++++++++++++---
> > >  1 file changed, 14 insertions(+), 3 deletions(-)
> > >
> > > Index: linux-2.6/drivers/ata/ahci.c
> > > ===================================================================
> > > --- linux-2.6.orig/drivers/ata/ahci.c 2007-05-03 11:06:33.000000000
> > +0800
> > > +++ linux-2.6/drivers/ata/ahci.c      2008-07-02 16:25:54.000000000
> > +0800
> > > @@ -1073,18 +1073,29 @@
> > >
> > >       /* global controller reset */
> > >       if (!ahci_skip_host_reset) {
> > > +             int delay = msecs_to_jiffies(1000);
> > > +             int timeout;
> > > +
> > >               tmp = readl(mmio + HOST_CTL);
> > >               if ((tmp & HOST_RESET) == 0) {
> > >                       writel(tmp | HOST_RESET, mmio + HOST_CTL);
> > >                       readl(mmio + HOST_CTL); /* flush */
> > >               }
> > >
> > > -             /* reset must complete within 1 second, or
> > > +             /*
> > > +              * to perform host reset, OS should set HOST_RESET
> > > +              * and poll until this bit is read to be "0"
> > > +              * reset must complete within 1 second, or
> > >                * the hardware should be considered fried.
> > >                */
> > > -             ssleep(1);
> > > +             timeout = jiffies + delay;
> > > +             while (jiffies < timeout) {
> > > +                     tmp = readl(mmio + HOST_CTL);
> > > +                     if (!(tmp & HOST_RESET))
> > > +                             break;
> > > +                     cpu_relax();
> > > +             }
> > Looks good in principle.  Just two things...
> >
> > 1. Please don't busy-loop.  e.g. No one would notice 10ms delay
> > between
> > polls.
> >
> > 2. Please use ata_wait_register().
> Thanks for review, refreshed patch attached. :)
>
> From: Zhang Rui <rui.zhang@xxxxxxxxx>
>
> During resume, sleep 1 second to wait for the HBA reset
> to finish is a waste of time.
>
> According to the AHCI 1.2 spec,
> We should poll the HOST_CTL register,
> and return error if the host reset is not
> finished within 1 second.
>
> Test results show that the HBA reset can be done quickly(in usecs).
> And this patch may save nearly 1 second during resume.
>
> Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
> --
>  drivers/ata/ahci.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/drivers/ata/ahci.c
> ===================================================================
> --- linux-2.6.orig/drivers/ata/ahci.c	2008-07-04 09:49:05.000000000 +0800
> +++ linux-2.6/drivers/ata/ahci.c	2008-07-04 11:31:30.000000000 +0800
> @@ -1079,12 +1079,15 @@
>  			readl(mmio + HOST_CTL); /* flush */
>  		}
>  
> -		/* reset must complete within 1 second, or
> +		/*
> + 		 * to perform host reset, OS should set HOST_RESET
> +		 * and poll until this bit is read to be "0".
> + 		 * reset must complete within 1 second, or
>  		 * the hardware should be considered fried.
>  		 */
> -		ssleep(1);
> +		tmp = ata_wait_register(mmio + HOST_CTL, HOST_RESET,
> +					HOST_RESET, 10, 1000);
>  
> -		tmp = readl(mmio + HOST_CTL);
>  		if (tmp & HOST_RESET) {
>  			dev_printk(KERN_ERR, host->dev,
>  				   "controller reset failed (0x%x)\n", tmp);

applied


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/