From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 1/3] pata_pdc202xx_old: fix UDMA mode for Promise UDMA33 cards Date: Sat, 13 Feb 2010 17:39:40 -0500 Message-ID: <4B772A2C.4050009@garzik.org> References: <20100213133538.11564.94218.sendpatchset@localhost> <20100213133553.11564.95723.sendpatchset@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-yw0-f179.google.com ([209.85.211.179]:46321 "EHLO mail-yw0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751543Ab0BMWjn (ORCPT ); Sat, 13 Feb 2010 17:39:43 -0500 In-Reply-To: <20100213133553.11564.95723.sendpatchset@localhost> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Bartlomiej Zolnierkiewicz Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Russell King On 02/13/2010 08:35 AM, Bartlomiej Zolnierkiewicz wrote: > From: Bartlomiej Zolnierkiewicz > 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 > Signed-off-by: Bartlomiej Zolnierkiewicz > --- > drivers/ata/pata_pdc202xx_old.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) applied