Messages in this thread | | | Date | Fri, 04 Jul 2008 11:48:40 +0900 | From | Tejun Heo <> | Subject | Re: [RFC PATCH] AHCI: speed up resume |
| |
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@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(); > + }
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.
-- tejun
| |