Re: + via-pata-controller-xfer-fixes.patch added to -mm tree

[Jeff Garzik <jeff@garzik.org>]

akpm@osdl.org wrote:
> The patch titled
> 
>      VIA PATA controller xfer fixes
> 
> has been added to the -mm tree.  Its filename is
> 
>      via-pata-controller-xfer-fixes.patch
> 
> See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
> out what to do about this
> 
> ------------------------------------------------------
> Subject: VIA PATA controller xfer fixes
> From: matthieu castet <castet.matthieu@free.fr>
> 
> 
> On via controller(vt8235) and pata via, some ATAPI devices (CDR-6S48) fail
> in the xfer mode initialisation.  This make the boot slow and the drive
> unsuable.
> 
> It seems the interrupt for xfer mode is done before the drive is ready, so
> the current libata code skip the interrupt.  But no new interrupt is done
> by the controller, so the xfer mode fails.
> 
> A quirk is to wait for 10 us (by step of 1 us) and see if the device
> becomes ready in the case of SETFEATURES_XFER feature.  The problem seems
> pata_via only, so the quirk is put in the pata_via interrupt handler as
> Tejun Heo request.
> 
> It won't affect working devices, as we don't wait if the device is already
> ready.  It will adds an extra ata_altstatus in order to avoid to duplicate
> ata_host_intr, but only in the case of SETFEATURES_XFER (with should happen
> only few times).
> 
> Sorry for the lack of changelog in my previous mail, I tought the old
> changelog + move it in pata via interrupt was enought.  And sorry again, I
> sent you a bad patch (I forgot a quitl refresh).

Data point #1:

Here I quote from drivers/ide generic code ide_config_drive_speed() in 
ide-iops.c:

    /*
     * Allow status to settle, then read it again.
     * A few rare drives vastly violate the 400ns spec here,
     * so we'll wait up to 10usec for a "good" status
     * rather than expensively fail things immediately.
     * This fix courtesy of Matthew Faupel & Niccolo Rigacci.
     */
    for (i = 0; i < 10; i++) {
            udelay(1);
            if (OK_STAT((stat = hwif->INB(IDE_STATUS_REG)),
			  DRIVE_READY, BUSY_STAT|DRQ_STAT|ERR_STAT)) {
                    error = 0;
                    break;
            }
    }

And there is similar logic in ide_wait_stat().  wait_drive_not_busy() in 
ide-taskfile.c waits for up to 1 ms.


Data point #2:

libata was originally based on the "highly correct" (or one version 
thereof) programming sequences found in Hale Landis's free ATADRVR 
(http://www.ata-atapi.com/).  Hale's ATADRVR, which was MS-DOS based and 
not threaded or asynchronous at all, did the following after every 
command execution (sent taskfile to hardware):

	if (device is ATAPI)
		sleep(150 ms)


Overall, I've no clue what to do on older PATA hardware, so my 
"insightful" suggestions are largely (a) follow drivers/ide code and/or 
(b) listen to any old fogies with deep historical knowledge.