linux-kernel - [PATCH] USB: isp1760: Soften DW3 X/transaction error bit handling

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Date:	Thu, 6 May 2010 23:15:32 +0400
From:	Anton Vorontsov <avorontsov@...sta.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	Sebastian Siewior <bigeasy@...utronix.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Bryan Wu <cooloney@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] USB: isp1760: Soften DW3 X/transaction error bit handling

There were some reports[1] of isp1760 USB driver malfunctioning
with high speed devices, noticed on Blackfin and PowerPC targets.
These reports indicated that the original Philips 'pehcd'[2]
driver worked fine.

We've noticed the same issue with an ARM RealView platform. This
happens under load (with only some mass storage devices, not all,
just as in another report[3]):

  error bit is set in DW3
  error bit is set in DW3
  error bit is set in DW3
  usb 1-1.2: device descriptor read/64, error -32

It appears that the 'pehcd' driver checks the X bit only if the
transaction is halted, otherwise the error is so far
insignificant.

I didn't find where exactly ISP1760 spec mandates 'H && X'
handling (maybe it's in the EHCI spec?), but the approach that
is used in the original driver (and in the EHCI driver, FWIW)
fixes the issue.

[1] http://markmail.org/message/lx4qrlbrs2uhcnly
[2] svn co svn://sources.blackfin.uclinux.org/linux-kernel/trunk/drivers/usb/host -r 5494
    See pehci.c:pehci_hcd_update_error_status().
[3] http://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?action=TrackerItemEdit&tracker_item_id=5148

Signed-off-by: Anton Vorontsov <avorontsov@...sta.com>
---

Note that this isn't related to the recent cache issues on ARM
platforms, as the kernel I'm running has commit 3f54ccf38eb51
'isp1760: Flush the D-cache for the pipe-in transfer buffers'.

 drivers/usb/host/isp1760-hcd.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c
index 9f01293..9989c0b 100644
--- a/drivers/usb/host/isp1760-hcd.c
+++ b/drivers/usb/host/isp1760-hcd.c
@@ -713,12 +713,11 @@ static int check_error(struct ptd *ptd)
 	u32 dw3;

 	dw3 = le32_to_cpu(ptd->dw3);
-	if (dw3 & DW3_HALT_BIT)
+	if (dw3 & DW3_HALT_BIT) {
 		error = -EPIPE;

-	if (dw3 & DW3_ERROR_BIT) {
-		printk(KERN_ERR "error bit is set in DW3\n");
-		error = -EPIPE;
+		if (dw3 & DW3_ERROR_BIT)
+			pr_err("error bit is set in DW3\n");
 	}

 	if (dw3 & DW3_QTD_ACTIVE) {
-- 
1.7.0.5
--
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