From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Subject: [PATCH] Fix Promise UDMA33 IDE driver (pdc202xx_old) Date: Sun, 3 Jan 2010 22:35:42 +0000 Message-ID: <20100103223542.GA24920@flint.arm.linux.org.uk> References: <20091224181300.GA4654@flint.arm.linux.org.uk> <20091224215451.GA2476@flint.arm.linux.org.uk> <20100103002314.GA16528@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:42622 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753036Ab0ACWf5 (ORCPT ); Sun, 3 Jan 2010 17:35:57 -0500 Content-Disposition: inline In-Reply-To: <20100103002314.GA16528@flint.arm.linux.org.uk> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: "David S. Miller" Cc: linux-ide@vger.kernel.org, Sergei Shtylyov On Sun, Jan 03, 2010 at 12:23:14AM +0000, Russell King wrote: > - with IDE > - locks the interrupt line, and makes the machine extremely painful - > about an hour to get to the point of being able to unload the > pdc202xx_old module. Having manually bisected kernel versions, I've narrowed it down to some change between 2.6.30 and 2.6.31. There's not much which has changed between the two kernels, but one change stands out like a sore thumb: +static int pdc202xx_test_irq(ide_hwif_t *hwif) +{ + struct pci_dev *dev = to_pci_dev(hwif->dev); + unsigned long high_16 = pci_resource_start(dev, 4); + u8 sc1d = inb(high_16 + 0x1d); + + if (hwif->channel) { + /* + * bit 7: error, bit 6: interrupting, + * bit 5: FIFO full, bit 4: FIFO empty + */ + return ((sc1d & 0x50) == 0x40) ? 1 : 0; + } else { + /* + * bit 3: error, bit 2: interrupting, + * bit 1: FIFO full, bit 0: FIFO empty + */ + return ((sc1d & 0x05) == 0x04) ? 1 : 0; + } +} Reading the (documented as a 32-bit) system control register when the interface is idle gives: 0x01da110c So, the byte at 0x1d is 0x11, which is documented as meaning that the primary and secondary FIFOs are empty. The code above, which is trying to see whether an IRQ is pending, checks for the IRQ bit to be one, and the FIFO bit to be zero - or in English, to be non-empty. Since during a BM-DMA read, the FIFOs will naturally be drained to the PCI bus, the chance of us getting to the interface before this happens are extremely small - and if we don't, it means we decide not to service the interrupt. Hence, the screaming interrupt problem with drivers/ide. Fix this by only indicating an interrupt is ready if both the interrupt and FIFO empty bits are at '1'. This bug only affects PDC20246/PDC20247 (Promise Ultra33) based cards, and has been tested on 2.6.31 and 2.6.33-rc2. Signed-off-by: Russell King Tested-by: Russell King --- drivers/ide/pdc202xx_old.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/ide/pdc202xx_old.c b/drivers/ide/pdc202xx_old.c index cb812f3..f5c08f4 100644 --- a/drivers/ide/pdc202xx_old.c +++ b/drivers/ide/pdc202xx_old.c @@ -100,13 +100,13 @@ static int pdc202xx_test_irq(ide_hwif_t *hwif) * bit 7: error, bit 6: interrupting, * bit 5: FIFO full, bit 4: FIFO empty */ - return ((sc1d & 0x50) == 0x40) ? 1 : 0; + return ((sc1d & 0x50) == 0x50) ? 1 : 0; } else { /* * bit 3: error, bit 2: interrupting, * bit 1: FIFO full, bit 0: FIFO empty */ - return ((sc1d & 0x05) == 0x04) ? 1 : 0; + return ((sc1d & 0x05) == 0x05) ? 1 : 0; } } -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: