linux-kernel - Re: [PATCH v4] fpga manager: Add Altera CvP driver

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Message-ID: <20170514103819.3035ef0e@crub>
Date:   Sun, 14 May 2017 10:38:19 +0200
From:   Anatolij Gustschin <agust@...x.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-fpga@...r.kernel.org,
        Alan Tull <atull@...nsource.altera.com>,
        Moritz Fischer <moritz.fischer@...us.com>,
        matthew.gerlach@...ux.intel.com, yi1.li@...ux.intel.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] fpga manager: Add Altera CvP driver

On Wed, 3 May 2017 18:01:19 +0300
Andy Shevchenko andy.shevchenko@...il.com wrote:
...
>> when 12 LSBs are zero, the bytes value has been decremented by
>> 4k, meaning that a new 4k data block has been written. Only
>> then the error checking is performed.  
>
>If the size is less than 4k...?

then the final check below will catch it. And I doubt that config
images can be so small. The lowest size I've ever seen is more
than 1MiB.

...
>>>> pci config space access works without enabling the pci device,
>>>> writing commands to config space enables the device first. It is done
>>>> some lines below which you deleted when commenting (please see original
>>>> patch).  
>>>
>>>Your comment didn't clarify what's going on along these lines.
>>>
>>>I checked original patch, I didn't find any type of
>>>pci_enable_device() call.  
>>  
>
>> I mean this part (instead of pci_enable_device()):  
>
>> +       /* Enable memory BAR access */
>> +       pci_read_config_word(pdev, PCI_COMMAND, &cmd);
>> +       if (!(cmd & PCI_COMMAND_MEMORY)) {
>> +               cmd |= PCI_COMMAND_MEMORY;
>> +               pci_write_config_word(pdev, PCI_COMMAND, cmd);
>> +       }  
>
>I see this code is used somewhere else (several places I suppose,
>drivers/video/fbdev/aty/atyfb_base.c is one of them).

other places set or clean additional pci command flags, use
different pci config accessors or contain debug code. And I reuse
pre-initialized cmd in the error path, so the usage pattern here
is not the same as in the atyfb_base driver.

--
Anatolij