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Subject[PATCH 1/3] pata_pdc202xx_old: fix UDMA mode for Promise UDMA33 cards
From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Subject: [PATCH] pata_pdc202xx_old: fix UDMA mode for Promise UDMA33 cards

On Monday 04 January 2010 02:30:24 pm Russell King wrote:

> Found the problem - getting rid of the read of the alt status register
> after the command has been written fixes the UDMA CRC errors on write:
>
> @@ -676,7 +676,8 @@ void ata_sff_exec_command(struct ata_port *ap, const struct
> ata_taskfile *tf)
> DPRINTK("ata%u: cmd 0x%X\n", ap->print_id, tf->command);
>
> iowrite8(tf->command, ap->ioaddr.command_addr);
> - ata_sff_pause(ap);
> + ndelay(400);
> +// ata_sff_pause(ap);
> }
> EXPORT_SYMBOL_GPL(ata_sff_exec_command);
>
>
> This rather makes sense. The PDC20247 handles the UDMA part of the
> protocol. It has no way to tell the PDC20246 to wait while it suspends
> UDMA, so that a normal register access can take place - the 246 ploughs
> on with the register access without any regard to the state of the 247.
>
> If the drive immediately starts the UDMA protocol after a write to the
> command register (as it probably will for the DMA WRITE command), then
> we'll be accessing the taskfile in the middle of the UDMA setup, which
> can't be good. It's certainly a violation of the ATA specs.

Fix it by adding custom ->sff_exec_command method for UDMA33 chipsets.

Debugged-by: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
drivers/ata/pata_pdc202xx_old.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
Index: b/drivers/ata/pata_pdc202xx_old.c
===================================================================
--- a/drivers/ata/pata_pdc202xx_old.c
+++ b/drivers/ata/pata_pdc202xx_old.c
@@ -2,7 +2,7 @@
* pata_pdc202xx_old.c - Promise PDC202xx PATA for new ATA layer
* (C) 2005 Red Hat Inc
* Alan Cox <alan@lxorguk.ukuu.org.uk>
- * (C) 2007,2009 Bartlomiej Zolnierkiewicz
+ * (C) 2007,2009,2010 Bartlomiej Zolnierkiewicz
*
* Based in part on linux/drivers/ide/pci/pdc202xx_old.c
*
@@ -26,6 +26,15 @@

#include "pata_pdc202xx_old.h"

+static void pdc20246_exec_command(struct ata_port *ap,
+ const struct ata_taskfile *tf)
+{
+ DPRINTK("ata%u: cmd 0x%X\n", ap->print_id, tf->command);
+
+ iowrite8(tf->command, ap->ioaddr.command_addr);
+ ndelay(400);
+}
+
/**
* pdc2026x_bmdma_start - DMA engine begin
* @qc: ATA command
@@ -171,6 +180,8 @@ static struct ata_port_operations pdc202
.cable_detect = ata_cable_40wire,
.set_piomode = pdc202xx_set_piomode,
.set_dmamode = pdc202xx_set_dmamode,
+
+ .sff_exec_command = pdc20246_exec_command,
};

static struct ata_port_operations pdc2026x_port_ops = {

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