linux-kernel - Re: [PATCH] net: macb: Align the dma and coherent dma masks

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Date:   Wed, 9 Feb 2022 11:24:43 +0100
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     Harini Katakam <harini.katakam@...inx.com>, <davem@...emloft.net>,
        <claudiu.beznea@...rochip.com>, <kuba@...nel.org>,
        <Conor.Dooley@...rochip.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <michal.simek@...inx.com>, <harinikatakamlinux@...il.com>,
        <mstamand@...na.com>
Subject: Re: [PATCH] net: macb: Align the dma and coherent dma masks

On 09/02/2022 at 10:43, Harini Katakam wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> From: Marc St-Amand <mstamand@...na.com>
> 
> Single page and coherent memory blocks can use different DMA masks
> when the macb accesses physical memory directly. The kernel is clever
> enough to allocate pages that fit into the requested address width.
> 
> When using the ARM SMMU, the DMA mask must be the same for single
> pages and big coherent memory blocks. Otherwise the translation
> tables turn into one big mess.
> 
>    [   74.959909] macb ff0e0000.ethernet eth0: DMA bus error: HRESP not OK
>    [   74.959989] arm-smmu fd800000.smmu: Unhandled context fault: fsr=0x402, iova=0x3165687460, fsynr=0x20001, cbfrsynra=0x877, cb=1
>    [   75.173939] macb ff0e0000.ethernet eth0: DMA bus error: HRESP not OK
>    [   75.173955] arm-smmu fd800000.smmu: Unhandled context fault: fsr=0x402, iova=0x3165687460, fsynr=0x20001, cbfrsynra=0x877, cb=1
> 
> Since using the same DMA mask does not hurt direct 1:1 physical
> memory mappings, this commit always aligns DMA and coherent masks.
> 
> Signed-off-by: Marc St-Amand <mstamand@...na.com>
> Signed-off-by: Harini Katakam <harini.katakam@...inx.com>

Ok:
Acked-by: Nicolas Ferre <nicolas.ferre@...rochip.com>

Best regards,
   Nicolas

> ---
>   drivers/net/ethernet/cadence/macb_main.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 1ce20bf52f72..4c231159b562 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -4765,7 +4765,7 @@ static int macb_probe(struct platform_device *pdev)
> 
>   #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
>          if (GEM_BFEXT(DAW64, gem_readl(bp, DCFG6))) {
> -               dma_set_mask(&pdev->dev, DMA_BIT_MASK(44));
> +               dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(44));
>                  bp->hw_dma_cap |= HW_DMA_CAP_64B;
>          }
>   #endif
> --
> 2.17.1
> 


-- 
Nicolas Ferre