linux-kernel - Re: [PATCH] drivers/ide/ide-probe.c, kernel 2.6.23.1

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Date:	Tue, 13 Nov 2007 23:03:28 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jonas Stare <jonas.stare@...plescout.se>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] drivers/ide/ide-probe.c, kernel 2.6.23.1


Hi,

On Monday 12 November 2007, Andrew Morton wrote:
> On Fri, 09 Nov 2007 11:22:41 +0100 Jonas Stare <jonas.stare@...plescout.se> wrote:
> 
> > Hi.
> > 
> > This week I ran into a strange hardware problem. During boot I got a 35 
> > second delay while waiting for IDE-disks that weren't there to report 

With what chipset and host driver does this happen?

> > that they were not in a BSY state. The problem was most likely in the 
> > hardware but this patch enables you to ignore waiting for disks by 
> > setting hdX=noprobe (and not setting the geometry by hand) as a kernel 
> > option.
> > 
> > If no noprobe-option is set the code will work (more or less) as the 
> > original but if set the code will skip the ide_wait_not_busy() for that 
> > drive. Even if there would be a drive there and it is still BSY 
> > afterwards it should not matter since it isn't probed for later.
> > 
> > There are other ways to get around the "35-seconds-of-waiting-in-vain", 
> > like actually fix the hardware, insert a second drive that works or 
> > recompile the kernel with edd-support builtin (atleast I've seen that 
> > solution on a forum) and possibly others. But this patch would allow 
> > people to get Linux to boot quickly on wonky hardware without having to 
> > recompile anything.
> 
> > (The code also honors the MAX_DRIVES variable instead of assuming that 
> > ther will be 2 drives on the bus.)
> 
> I keep on hearing about problems with boot-time IDE probing.  It's public
> enemy #1 with the embedded guys.

The problem is that we are not hearing about them.

Please forward the reports to linux-ide@...r.kernel.org.

> It does seem that operator intervention is needed in some fashion.
> 
> > I will be happy for all the comments I can get. :) But be gentle, this 
> > is my first patch...

Jonas, could you also put printk() dumping content of 'stat' in
ide-iops.c::ide_wait_not_busy() so we can verify that it is not
some problem with ide_wait_not_busy() itself.

> >    Best regards
> >    Jonas Stare
> > 
> > Signed-off-by: Jonas Stare <jonas.stare@...plescout.se>
> > --
> > diff -u linux-2.6.23.1-orig/drivers/ide/ide-probe.c 
> > linux-2.6.23.1/drivers/ide/ide-probe.c
> > --- linux-2.6.23.1-orig/drivers/ide/ide-probe.c 2007-10-12 
> > 18:43:44.000000000 +0200
> > +++ linux-2.6.23.1/drivers/ide/ide-probe.c      2007-11-09 
> > 10:43:16.000000000 +0100
> > @@ -643,6 +643,7 @@
> >   static int wait_hwif_ready(ide_hwif_t *hwif)
> >   {
> >          int rc;
> > +       int unit;
> > 
> >          printk(KERN_DEBUG "Probing IDE interface %s...\n", hwif->name);
> > 
> > @@ -659,20 +660,24 @@
> >                  return rc;
> > 

Hmm, so the first ide_wait_not_busy() (for the currently
selected device) is OK and doesn't stall?

> >          /* Now make sure both master & slave are ready */
> > -       SELECT_DRIVE(&hwif->drives[0]);
> > -       hwif->OUTB(8, hwif->io_ports[IDE_CONTROL_OFFSET]);
> > -       mdelay(2);
> > -       rc = ide_wait_not_busy(hwif, 35000);
> > -       if (rc)
> > -               return rc;
> > -       SELECT_DRIVE(&hwif->drives[1]);
> > -       hwif->OUTB(8, hwif->io_ports[IDE_CONTROL_OFFSET]);
> > -       mdelay(2);
> > -       rc = ide_wait_not_busy(hwif, 35000);
> > +       for (unit = 0; unit < MAX_DRIVES; ++unit) {
> > +               /* Ignore disks that we will not probe for later. */
> > +               if (!hwif->drives[unit].noprobe ||
> > +                   hwif->drives[unit].forced_geom) {

It is better to check for ->present
(->forced_geom implies that ->present is set).

> > +                       SELECT_DRIVE(&hwif->drives[unit]);
> > +                       hwif->OUTB(8, hwif->io_ports[IDE_CONTROL_OFFSET]);
> > +                       mdelay(2);
> > +                       rc = ide_wait_not_busy(hwif, 35000);
> > +                       /* Exit function with master selected (let's be 
> > sane) */
> > +                       SELECT_DRIVE(&hwif->drives[0]);

This changes the previous behavior adding an extra SELECT_DRIVE()
before trying the slave drive.

> > +                       if (rc)
> > +                               return rc;
> > +               } else {
> > +                       printk(KERN_DEBUG "Skip ide_wait_not_busy for 
> > %s:%d\n",
> > +                         hwif->name, unit);
> > +               }
> > +       }
> > 
> > -       /* Exit function with master reselected (let's be sane) */
> > -       SELECT_DRIVE(&hwif->drives[0]);
> > -
> >          return rc;
> >   }
> 
> Maybe that's the fix, maybe not - I'll defer to others on that (please).
> 
> Your email client is wordwrapping the text, and replaces tabs with spaces. 
> Most of them seem to do this nowadays.  For thunderbird, please see
> http://mbligh.org/linuxdocs/Email/Clients/Thunderbird
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