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From: khalasa@piap.pl (Krzysztof =?utf-8?Q?Ha=C5=82asa?=)
To: Andrey Utkin <andrey_utkin@fastmail.com>
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Subject: Re: solo6010 modprobe lockup since e1ceb25a (v4.3 regression)
References: <20160915130441.ji3f3jiiebsnsbct@acer>
        <9cbb2079-f705-5312-d295-34bc3c8dadb9@xs4all.nl>
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        <m3ponri5ky.fsf@t19.piap.pl> <20160926091831.cp6qkv77oo5tinn5@zver>
Date: Tue, 27 Sep 2016 07:27:53 +0200
In-Reply-To: <20160926091831.cp6qkv77oo5tinn5@zver> (Andrey Utkin's message of
        "Mon, 26 Sep 2016 12:18:31 +0300")
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Andrey Utkin <andrey_utkin@fastmail.com> writes:

>> Does (only) adding the
>> 
>> 	pci_read_config_word(solo_dev->pdev, PCI_STATUS, &val);
>> 
>> in solo_reg_write() help?
>
> Yes.
> I have posted a patch with this change few days ago, I thought you have
> noticed it.

Well, I think you haven't sent me a copy. Anyway, it would be great to
determine where exactly writes need a flush. Adding it everywhere is a
bit suboptimal, one would think.

Can you share some details about the machine you are experiencing the
problems on? CPU, chipset? I'd try to see if I can recreate the problem.

Alternatively, you could investigate yourself - at first you could put
pci_read_config_word() at the end of subroutines (including return
statements) using solo_reg_write(). And in that solo_p2m_dma_desc(),
before wait_for_completion_timeout(). Then eliminate them using some
sort of binary search to see which ones are required.
-- 
Krzysztof Halasa

Industrial Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland