netdev - RE: [PATCH v2] r8169: set coherent DMA mask as well as streaming DMA mask

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Date:   Fri, 14 Oct 2016 13:42:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Ard Biesheuvel' <ard.biesheuvel@...aro.org>,
        "romieu@...zoreil.com" <romieu@...zoreil.com>,
        "nic_swsd@...ltek.com" <nic_swsd@...ltek.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH v2] r8169: set coherent DMA mask as well as streaming
 DMA mask

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 ?

	David