Re: [PATCH] Fix pio/mwdma programming on ata_piix.c

["Art Haas" <ahaas@airmail.net>]

On Tue, May 01, 2007 at 05:02:22AM +0200, Tejun Heo wrote:
> Hello, Art Haas.
> 
> Art Haas wrote:
> > Hi.
> > 
> > Back in the beginning of February I was sent a patch to test during the
> > time the CD-ROM identification bug was affecting my computer. The
> > first posting of the patch appeared on Feb. 3 with Tejun Heo writing:
> 
> Ah.. I completely forgot about this one.  This wasn't directly related
> to the detection bug, so I got oblivious as usual.  :-)
> 
> I think Alan has reviewed it back then.  If there's no objection, I'll
> reformat the patch and submit it properly.  Quoting whole message for Jeff.
> 
> >> Hello, Art Haas, Alan.
> >>
> >> Okay, here's another try at fixing the detection bug.  I went through
> >> intel ich docs and compared with the ide piix driver.  This patch
> >> fixes the following problems.
> >>
> >> * Control bits in the timing register wasn't cleared properly while
> >>   programming PIO mode.
> >>
> >> * MWDMA mode programming cleared the wrong part of control bits.  I
> >>   think this can fix your problem.
> >>
> >> * MWDMA mode programming cleared udma_mask even when the controller
> >>   doesn't support UDMA.  This doesn't matter for your case.
> >>
> >> Please test and report the result.  Thanks.
> > 
> > The patch and complete thread can be reviewed here:
> > 
> > http://marc.info/?l=linux-ide&m=117042956705812&w=2
> > 
> > Now that 2.6.22 is open for big modifications, and the queued libata
> > changes have been pulled by Linus, I'm wondering if the ata_piix.c patch
> > posted above should be sent. I've built all my kernels since the posting
> > with the patch and had no problems. As you write above, the patch does
> > fix some bugs, and as the thread progressed a cleanup or two in the code
> > was explained as a bug fix - the setting of the 'slave_data' variable
> > between lines 826 and 834 in particular.
> > 
> > Here's the patch against today's Linus tree if you feel it should make
> > it into 2.6.22.
> > [ ... snip ... ]

Ping?

Here's the patch diffed to this afternoon's tree.

Art Haas

diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index 0458811..51de738 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -684,8 +684,14 @@ static void piix_set_piomode (struct ata_port *ap, struct ata_device *adev)
 	if (adev->class == ATA_DEV_ATA)
 		control |= 4;	/* PPE enable */
 
+	/* PIO configuration clears DTE unconditionally.  It will be
+	 * programmed in set_dmamode which is guaranteed to be called
+	 * after set_piomode if any DMA mode is available.
+	 */
 	pci_read_config_word(dev, master_port, &master_data);
 	if (is_slave) {
+		/* clear TIME1|IE1|PPE1|DTE1 */
+		master_data &= 0xff0f;
 		/* Enable SITRE (seperate slave timing register) */
 		master_data |= 0x4000;
 		/* enable PPE1, IE1 and TIME1 as needed */
@@ -693,12 +699,14 @@ static void piix_set_piomode (struct ata_port *ap, struct ata_device *adev)
 		pci_read_config_byte(dev, slave_port, &slave_data);
 		slave_data &= (ap->port_no ? 0x0f : 0xf0);
 		/* Load the timing nibble for this slave */
-		slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << (ap->port_no ? 4 : 0);
+		slave_data |= ((timings[pio][0] << 2) | timings[pio][1])
+						<< (ap->port_no ? 4 : 0);
 	} else {
-		/* Master keeps the bits in a different format */
-		master_data &= 0xccf8;
+		/* clear ISP|RCT|TIME0|IE0|PPE0|DTE0 */
+		master_data &= 0xccf0;
 		/* Enable PPE, IE and TIME as appropriate */
 		master_data |= control;
+		/* load ISP and RCT */
 		master_data |=
 			(timings[pio][0] << 12) |
 			(timings[pio][1] << 8);
@@ -815,7 +823,7 @@ static void do_pata_set_dmamode (struct ata_port *ap, struct ata_device *adev, i
 			master_data &= 0xFF4F;  /* Mask out IORDY|TIME1|DMAONLY */
 			master_data |= control << 4;
 			pci_read_config_byte(dev, 0x44, &slave_data);
-			slave_data &= (0x0F + 0xE1 * ap->port_no);
+			slave_data &= (ap->port_no ? 0x0f : 0xf0);
 			/* Load the matching timing */
 			slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << (ap->port_no ? 4 : 0);
 			pci_write_config_byte(dev, 0x44, slave_data);
@@ -827,8 +835,11 @@ static void do_pata_set_dmamode (struct ata_port *ap, struct ata_device *adev, i
 				(timings[pio][0] << 12) |
 				(timings[pio][1] << 8);
 		}
-		udma_enable &= ~(1 << devid);
-		pci_write_config_word(dev, master_port, master_data);
+
+		if (ap->udma_mask) {
+			udma_enable &= ~(1 << devid);
+			pci_write_config_word(dev, master_port, master_data);
+		}
 	}
 	/* Don't scribble on 0x48 if the controller does not support UDMA */
 	if (ap->udma_mask)

-- 
Man once surrendering his reason, has no remaining guard against absurdities
the most monstrous, and like a ship without rudder, is the sport of every wind.

-Thomas Jefferson to James Smith, 1822