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

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Date:	Mon, 12 Nov 2007 13:24:48 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jonas Stare <jonas.stare@...plescout.se>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] drivers/ide/ide-probe.c, kernel 2.6.23.1

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 
> 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.

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...
> 
>    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;
> 
>          /* 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) {
> +                       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]);
> +                       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).

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