On Tue, Jan 30, 2007 at 03:37:36PM -0800, Gary Hade wrote:
> On Tue, Jan 30, 2007 at 04:32:34PM +0900, Tejun Heo wrote:
> > Hello, Gary.
> >
> > Gary Hade wrote:
> > >>> If they verify your fix (ie,
> > >>> GoVault sometimes take more than 150ms to transmit the first D2H Reg FIs
> > >>> after SRST), I'll push similar patch upstream.
> > >> Thanks. If you think that changes to increase the delays are
> > >> the way to go (at least until we can find a better solution)
> > >> I can provide patches.
> > >
> > > Tejun,
> > > I haven't heard anything from you on this so I'm including a delay
> > > increase patch against 2.6.20-rc6 for the 'ata-piix' case below.
> > > I hope that you, Jeff, and others find this acceptable.
> >
> > Sorry about being unresponsive. The thing is that the change adds
> > unnecessary 2 secs of delay to a lot of other normal device-not-present
> > cases, so I was hesitant to ack the patch. I'll give it more thoughts
> > (and respond timely this time :-)
>
> Thanks! My followup was untimely so we're even. :-)
>
> Some of my random thoughts:
> There does appear to be this invalid assumption that 0xFF status
> always implies device-not-present. The status register access
> restrictions in ATA/ATAPI-7 V1 5.14.2 include the statement "The
> contents of this register, except for BSY, shall be ignored when
> BSY is set to one." which the code does not honor. There is apparently
> past experience that 0xFF status implies device-not-present for some
> controllers (the odd clowns :) but I have no idea how common these are.
> We obviously can't get rid of the check but since we cannot clear
> the read-only status register and there appears to be no specification
> dictated upper limit on how long it should take for a software reset to
> complete it just seems like we need to wait long enough to support the
> slowest known device which may be the GoVault.
>
> >
> > > With respect to the 'ahci' case w/2.6.20-rc6 the GoVault device is
> > > useable following boot although the below messages are being logged
> > > during initialization. Please let me know if you have any thoughts
> > > on this.
> > > scsi1 : ahci
> > > ata2: softreset failed (port busy but CLO unavailable)
> > > ata2: softreset failed, retrying in 5 secs
> > > ata2: port is slow to respond, please be patient (Status 0x80)
> > > ata2: port failed to respond (30 secs, Status 0x80)
> > > ata2: COMRESET failed (device not ready)
> > > ata2: hardreset failed, retrying in 5 secs
> > > ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
> > > ata2.00: ATAPI, max UDMA/66
> > > ata2.00: configured for UDMA/66
> >
> > The above should have been fixed in 2.6.20-rc6. Please test it. It was
> > caused by the ahci driver incorrectly clearing ahci CAP register and
> > fixed recently.
>
> I'm clearly seeing this with 2.6.20-rc6 but unlike the ata-piix
> issue it does not appear to be dependent on the port to which the
> device is attached. I've been playing around with this today and
> found that it could be solved by inserting a delay between the
> ahci_stop_engine() call and BSY/DRQ check.
>
> This change:
> --- linux-2.6.20-rc6/drivers/ata/ahci.c.orig 2007-01-30 11:01:20.000000000 -0800
> +++ linux-2.6.20-rc6/drivers/ata/ahci.c 2007-01-30 12:59:38.000000000 -0800
> @@ -804,6 +804,19 @@ static int ahci_softreset(struct ata_por
> goto fail_restart;
> }
>
> + {
> + int delay;
> + u8 stat;
> + for (delay = 0; delay < 2000; delay+=100) {
> + if (!(ahci_check_status(ap) & (ATA_BUSY | ATA_DRQ)))
> + break;
> + msleep(100);
> + stat = ahci_check_status(ap);
> + ata_port_printk(ap, KERN_INFO, "delay=%d BSY=%d DRQ=%d\n",
> + delay, (stat & ATA_BUSY)?1:0, (stat & ATA_DRQ)?1:0);
> + }
> + }
> +
> /* check BUSY/DRQ, perform Command List Override if necessary */
> if (ahci_check_status(ap) & (ATA_BUSY | ATA_DRQ)) {
> rc = ahci_clo(ap);
>
> Yielded this output both with and without the RDC inserted:
> scsi1 : ahci
> ata2: delay=0 BSY=1 DRQ=0
> ata2: delay=100 BSY=1 DRQ=0
> ata2: delay=200 BSY=1 DRQ=0
> ata2: delay=300 BSY=1 DRQ=0
> ata2: delay=400 BSY=1 DRQ=0
> ata2: delay=500 BSY=1 DRQ=0
> ata2: delay=600 BSY=1 DRQ=0
> ata2: delay=700 BSY=1 DRQ=0
> ata2: delay=800 BSY=1 DRQ=0
> ata2: delay=900 BSY=1 DRQ=0
> ata2: delay=1000 BSY=1 DRQ=0
> ata2: delay=1100 BSY=1 DRQ=0
> ata2: delay=1200 BSY=0 DRQ=0
> ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
> ata2.00: ATAPI, max UDMA/66
> ata2.00: configured for UDMA/66
>
> So it appears that we may also have a similar device slowness issue
> with this driver.
Tejun,
I instrumented the code and found that for the SATA hard drive BSY was set
just before the call to ahci_init_port() from ahci_port_start() and clear
after the return from ahci_init_port(). For the GoVault BSY was still set
after the return from ahci_init_port() and remained set for almost 2 seconds.
The below patch which gives BSY some extra time to clear repairs the problem.
Unlike the extra delay for ata-piix needed by GoVault I believe this delay
will only be seen for attached devices that need it. Please let me know
what you think.
Thanks.
Gary
--
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503 IBM T/L: 775-4503
garyhade@xxxxxxxxxx
http://www.ibm.com/linux/ltc
We encountered a problem where the BSY status bit is still
set on entry to the 'ahci' error handler during initialization
of the Quantum GoVault when attached to an ICH6R/ICH6RW controller.
This caused a software reset failure due to failed BSY/DRQ check
forcing a hard reset with the following messages logged.
ata1: softreset failed (port busy but CLO unavailable)
ata1: softreset failed, retrying in 5 secs
ata1: port is slow to respond, please be patient (Status 0x80)
ata1: port failed to respond (30 secs, Status 0x80)
ata1: COMRESET failed (device not ready)
ata1: hardreset failed, retrying in 5 secs
It was taking almost 2 seconds for BSY to clear following the
return from ahci_init_port() in ahci_port_start() so this patch
gives BSY up to 3 seconds extra time to clear eliminating the
problem.
Signed-off-by: Gary Hade <garyhade@xxxxxxxxxx>
--- linux-2.6.20-rc7/drivers/ata/ahci.c.orig 2007-02-16 10:11:21.000000000 -0800
+++ linux-2.6.20-rc7/drivers/ata/ahci.c 2007-02-16 13:23:04.000000000 -0800
@@ -1423,6 +1423,8 @@ static int ahci_port_start(struct ata_po
void *mem;
dma_addr_t mem_dma;
int rc;
+ u8 status;
+ unsigned long timeout;
pp = kmalloc(sizeof(*pp), GFP_KERNEL);
if (!pp)
@@ -1477,6 +1479,17 @@ static int ahci_port_start(struct ata_po
/* initialize port */
ahci_init_port(port_mmio, hpriv->cap, pp->cmd_slot_dma, pp->rx_fis_dma);
+ status = ahci_check_status(ap);
+
+ /* for some devices we need to delay to allow BSY to clear */
+ if (status & ATA_BUSY) {
+ timeout = jiffies + 3*HZ;
+ while ((status & ATA_BUSY) && time_before(jiffies, timeout)) {
+ msleep(50);
+ status = ahci_check_status(ap);
+ }
+ }
+
return 0;
}
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