From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [RFC PATCH] AHCI: speed up resume Date: Fri, 11 Jul 2008 09:49:45 -0400 Message-ID: <487764F9.20908@garzik.org> References: <1215074882.3214.15.camel@rzhang-dt.sh.intel.com> <486D8F88.9000904@kernel.org> <1215149537.3068.18.camel@rzhang-dt.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1215149537.3068.18.camel@rzhang-dt.sh.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Zhang Rui Cc: Tejun Heo , linux-pm , linux-kernel List-Id: linux-pm@vger.kernel.org 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 >>> -- >>> 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 > > 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 > -- > 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