linux-kernel - Re: [PATCH v2] r8169: set coherent DMA mask as well as streaming DMA mask

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Message-Id: <20161015.173108.998320512006202215.davem@davemloft.net>
Date:   Sat, 15 Oct 2016 17:31:08 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     ard.biesheuvel@...aro.org
Cc:     David.Laight@...LAB.COM, romieu@...zoreil.com,
        nic_swsd@...ltek.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] r8169: set coherent DMA mask as well as streaming
 DMA mask

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Date: Fri, 14 Oct 2016 14:48:51 +0100

> 
>> On 14 Oct 2016, at 14:42, David Laight <David.Laight@...LAB.COM> wrote:
>> 
>> From: Of Ard Biesheuvel
>>> Sent: 14 October 2016 14:41
>>> 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@...aro.org>
>>> ---
>>> v2: dropped the hunk that sets the coherent DMA mask to DMA_BIT_MASK(32),
>>>    which is unnecessary given that it is the default
>>> 
>>> drivers/net/ethernet/realtek/r8169.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
>>> index e55638c7505a..bf000d819a21 100644
>>> --- a/drivers/net/ethernet/realtek/r8169.c
>>> +++ b/drivers/net/ethernet/realtek/r8169.c
>>> @@ -8273,7 +8273,8 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>>>    if ((sizeof(dma_addr_t) > 4) &&
>>>        (use_dac == 1 || (use_dac == -1 && pci_is_pcie(pdev) &&
>>>                  tp->mac_version >= RTL_GIGA_MAC_VER_18)) &&
>>> -        !pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) {
>>> +        !pci_set_dma_mask(pdev, DMA_BIT_MASK(64)) &&
>>> +        !pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64))) {
>> 
>> Isn't there a dma_set_mask_and_coherent() function ?
>> 
> 
> Not of the pci_xxx variety afaik

You can often use the "dev_*" variants intechangably with the pci_*()
ones.

In fact you'll find that for several architectures pci_*() is
implemented via calls to dev_*().