linux-kernel - Re: [PATCH] usb: pci-quirks: do not access OHCI

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Date:	Wed, 28 May 2014 11:12:27 +0400
From:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Mathias Nyman <mathias.nyman@...el.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, lugovskoy@....rtsoft.ru
Subject: Re: [PATCH] usb: pci-quirks: do not access OHCI_FMINTERVAL register
 on ULI hw

28.05.2014 03:27, Greg Kroah-Hartman пишет:
> On Tue, May 27, 2014 at 08:56:42AM +0400, Nikita Yushchenko wrote:
>> This access causes hang on Freescale P2020DS board (that has OHCI
>> provided by ULI 1533 chip).
>>
>> Since preserving OHCI_FMINTERVAL was originally done only for NVIDIA
>> hardware and only later (in c6187597) was turned unconditional, and
>> c6187597 commit message again mentions only NVIDIA, I think it should be
>> safe to disable preserving OHCI_FMINTERVAL if device vendor is ULI.
> 
> Have you tested this?

With this applied, board boots ok.
With this not applied, board hangs on boot.

As for OHCI functionality - this was tested by other people here, but with
older kernel. Will retest myself with 3.15-rc as soon as get physical access
to board.

>> -	u32 fminterval;
>> +	u32 uninitialized_var(fminterval);
> 
> Why is this change needed?  Sounds like a compiler bug to me :)

  CC      drivers/usb/host/pci-quirks.o
In file included from include/linux/io.h:22:0,
                 from include/linux/pci.h:31,
                 from drivers/usb/host/pci-quirks.c:14:
drivers/usb/host/pci-quirks.c: In function 'quirk_usb_early_handoff':
/home/cge7/nikita/kernel-u/arch/powerpc/include/asm/io.h:180:1: warning: 'fminterval' may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/usb/host/pci-quirks.c:574:6: note: 'fminterval' was declared here

gcc version 4.7.0 (MontaVista Linux G++ 4.7-140519214821)


Nikita
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