linux-kernel - Re: [PATCH v2] OHCI: add a quirk for ULi M5237 blocking on reset

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Message-ID: <5498FF69.2080000@kb.kras.ru>
Date:	Tue, 23 Dec 2014 12:36:41 +0700
From:	Arseny Solokha <asolokha@...kras.ru>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] OHCI: add a quirk for ULi M5237 blocking on reset

> On Sat, 6 Dec 2014, Arseny Solokha wrote:
> 
>> From: Arseny Solokha <asolokha@...kras.ru>
>>
>> Commit 8dccddbc2368 ("OHCI: final fix for NVIDIA problems (I hope)")
>> introduced into 3.1.9 broke boot on e.g. Freescale P2020DS development
>> board. The code path that was previously specific to NVIDIA controllers
>> had then become taken for all chips.
>>
>> However, the M5237 installed on the board wedges solid when accessing
>> its base+OHCI_FMINTERVAL register, making it impossible to boot any
>> kernel newer than 3.1.8 on this particular and apparently other similar
>> machines.
>>
>> Don't readl() and writel() base+OHCI_FMINTERVAL on PCI ID 10b9:5237.
>>
>> The patch is suitable for the -next tree as well as all maintained
>> kernels up to 3.2 inclusive.
>>
>> Signed-off-by: Arseny Solokha <asolokha@...kras.ru>
>> ---
>> Changes in v2:
>> - review comments applied
> 
> Much better this time.
> 
> Acked-by: Alan Stern <stern@...land.harvard.edu>

Meanwhile, I discovered a similar thread where the issue was previously
discussed, and have tried to implement a workaround suggested in [1]. No luck so
far: even if the code manages to check a value returned by
readl(base + OHCI_FMINTERVAL), it then still hangs during device unregistering.

Of course, unregistering a device instead of just not accessing OHCI_FMINTERVAL
like in my or Nikita's patch is also possible but it requires hardcoding all
flawed device IDs instead of figuring out misbehaving devices at boot time.


[1] https://lkml.org/lkml/2014/5/29/828

Arsény
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