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SubjectRe: [RFC PATCH] AHCI: speed up resume
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On Fri, 2008-07-04 at 07:23 +0800, Rafael J. Wysocki wrote:
> On Thursday, 3 of July 2008, 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.
>
> That's a lot.
>
> How heavily has it been tested?

I only tested it on a SantaRosa laptop.

w/o the patch,
[ 469.923186] ahci_pci_device_resume
[ 469.936105] PM: Writing back config space on device 0000:00:1f.2 at
offset f (was 200, writing 20a)
[ 469.936145] PM: Writing back config space on device 0000:00:1f.2 at
offset 1 (was 2b00007, writing 2b00407)
[ 469.936220] PCI: Setting latency timer of device 0000:00:1f.2 to 64
[ 470.092053] ata4.00: ACPI cmd ef/03:0c:00:00:00:a0 filtered out
[ 470.092053] ata4.00: ACPI cmd ef/03:42:00:00:00:a0 filtered out
[ 470.107675] ata4.00: configured for UDMA/33
[ 470.942195] ahci_pci_device_resume done
w/ the patch applied, run S3 for more than ten times in a row,
[ 571.150339] ahci_pci_device_resume
[ 571.163193] ahci_pci_device_resume done
[ 578.560382] ahci_pci_device_resume
[ 578.576410] ahci_pci_device_resume done
[ 586.065037] ahci_pci_device_resume
[ 586.080806] ahci_pci_device_resume done
[ 770.231756] ahci_pci_device_resume
[ 770.244431] ahci_pci_device_resume done
[ 777.537985] ahci_pci_device_resume
[ 777.553709] ahci_pci_device_resume done
[ 784.805554] ahci_pci_device_resume
[ 784.819660] ahci_pci_device_resume done
[ 791.888451] ahci_pci_device_resume
[ 791.905222] ahci_pci_device_resume done
[ 798.943719] ahci_pci_device_resume
[ 798.959437] ahci_pci_device_resume done
[ 806.438784] ahci_pci_device_resume
[ 806.452070] ahci_pci_device_resume done
[ 813.890609] ahci_pci_device_resume
[ 813.903247] ahci_pci_device_resume done
[ 821.265956] ahci_pci_device_resume
[ 821.278714] ahci_pci_device_resume done
[ 828.609051] ahci_pci_device_resume
[ 828.621795] ahci_pci_device_resume done
[ 835.731528] ahci_pci_device_resume
[ 835.744210] ahci_pci_device_resume done

I don't know if this ssleep(1) is required for some platform specific
problems, but this patch does work well for me. :)
Hmm, we'd better get some comments from Tejun Heo first.

thanks,
rui
>
> > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> > --
> > 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();
> > + }
> >
> > - tmp = readl(mmio + HOST_CTL);
> > if (tmp & HOST_RESET) {
> > dev_printk(KERN_ERR, host->dev,
> > "controller reset failed (0x%x)\n",
> tmp);
> >
> >
> >
> >
>
>
>
> --
> "Premature optimization is the root of all evil." - Donald Knuth
>
>



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