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

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Hi, thanks for the reply. :)

Bartlomiej Zolnierkiewicz wrote:
Hi,

On Monday 12 November 2007, Andrew Morton wrote:
On Fri, 09 Nov 2007 11:22:41 +0100 Jonas Stare <jonas.stare@xxxxxxxxxxxxxx> 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?

I am not sure about the chip-set but I think it was vt82c686b. It used the via82cxxx-driver, but only _after_ using the generic ide-code to probe/wait (a long time) for the disks. (This was in Suse 10.1 SP 1.)

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@xxxxxxxxxxxxxxxx

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.


Sorry. :( I don't have access to the hardware anymore (which is a "home-made" embedded machine). But from what I could get from poking around was that the BSY-bit on the slave (that never has or ever will exists) was set, probably because those who built the thing wanted to save money and/or space on that "billionth of a cent"-resistor that Alan Cox talked about.

   Best regards
   Jonas Stare

Signed-off-by: Jonas Stare <jonas.stare@xxxxxxxxxxxxxx>
--
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?


It didn't stall for me... But even if it had, probe_hwif() will ignore the entire controller if you set "idex=noprobe".

(From drivers/ide/ide-probe.c)

static void probe_hwif(ide_hwif_t *hwif, void (*fixup)(ide_hwif_t *hwif))
{
        unsigned int unit;
        unsigned long flags;
        unsigned int irqd;

        if (hwif->noprobe)
                return;


         /* 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).


Great comment. :) I'll change that right away...

+                       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.


Mmmm, yes, I know. But I couldn't come up with a clean and nice way to be sure that the first drive is selected. Maybe I could move it inside the if-statement below?

+                       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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