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Date: Fri, 14 Oct 2016 09:34:03 -0400 (EDT)
Message-Id: <20161014.093403.1591217631213879011.davem@davemloft.net>
To: ard.biesheuvel@linaro.org
Cc: romieu@fr.zoreil.com, nic_swsd@realtek.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] r8169: set coherent DMA mask as well as streaming DMA
 mask
From: David Miller <davem@davemloft.net>
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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Fri, 14 Oct 2016 14:32:24 +0100

> On 14 October 2016 at 14:31, David Miller <davem@davemloft.net> wrote:
>> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Date: Fri, 14 Oct 2016 12:39:30 +0100
>>
>>> PCI devices that are 64-bit DMA capable should set the coherent
>>> DMA mask as well as the streaming DMA mask. On some architectures,
>>> these are managed separately, and so the coherent DMA mask will be
>>> left at its default value of 32 if it is not set explicitly. This
>>> results in errors such as
>>>
>>>      r8169 Gigabit Ethernet driver 2.3LK-NAPI loaded
>>>      hwdev DMA mask = 0x00000000ffffffff, dev_addr = 0x00000080fbfff000
>>>      swiotlb: coherent allocation failed for device 0000:02:00.0 size=4096
>>>      CPU: 0 PID: 1062 Comm: systemd-udevd Not tainted 4.8.0+ #35
>>>      Hardware name: AMD Seattle/Seattle, BIOS 10:53:24 Oct 13 2016
>>>
>>> on systems without memory that is 32-bit addressable by PCI devices.
>>>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>  ...
>>> @@ -8281,6 +8282,8 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>>>               dev->features |= NETIF_F_HIGHDMA;
>>>       } else {
>>>               rc = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
>>> +             if (!rc)
>>> +                     rc = pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32));
>>
>> As you state 32-bit is the default, therefore this part of your patch is unnecessary.
> 
> Perhaps, but the original code did not assume that either. Should I
> remove the other call in a subsequent patch as well?

I simply want you to respin this with the above hunk removed.

Your code changes and your commit message must be consistent.