linux-kernel - Re: [PATCH] mmc: sunxi-mmc: Fix DMA descriptors allocated above 32 bits

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Message-ID: <20220425120334.62f60978@donnerap.cambridge.arm.com>
Date:   Mon, 25 Apr 2022 12:03:34 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maxime Ripard <maxime@...no.tech>,
        Yangtao Li <frank@...winnertech.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH] mmc: sunxi-mmc: Fix DMA descriptors allocated above 32
 bits

On Sun, 24 Apr 2022 18:17:50 -0500
Samuel Holland <samuel@...lland.org> wrote:

Hi Samuel,

thanks for sending this.

> Newer variants of the MMC controller support a 34-bit physical address
> space by using word addresses instead of byte addresses. However, the
> code truncates the DMA descriptor address to 32 bits before applying the
> shift. This breaks DMA for descriptors allocated above the 32-bit limit.
> 
> Fixes: 3536b82e5853 ("mmc: sunxi: add support for A100 mmc controller")
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
> 
>  drivers/mmc/host/sunxi-mmc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index c62afd212692..46f9e2923d86 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -377,8 +377,9 @@ static void sunxi_mmc_init_idma_des(struct sunxi_mmc_host *host,
>  		pdes[i].buf_addr_ptr1 =
>  			cpu_to_le32(sg_dma_address(&data->sg[i]) >>
>  				    host->cfg->idma_des_shift);
> -		pdes[i].buf_addr_ptr2 = cpu_to_le32((u32)next_desc >>
> -						    host->cfg->idma_des_shift);
> +		pdes[i].buf_addr_ptr2 =
> +			cpu_to_le32(next_desc >>
> +				    host->cfg->idma_des_shift);

I had mentioned this problem on the original patch before[1] and had
this fixed in my re-submission[2], so it looks good to me:

Reviewed-by: Andre Przywara <andre.przywara@....com>

Cheers,
Andre

[1]https://lore.kernel.org/linux-arm-kernel/65401815-cb2e-58ec-7653-f09d6a25804c@arm.com/
[2]https://lore.kernel.org/linux-arm-kernel/20210118020848.11721-3-andre.przywara@arm.com/

>  	}
>  
>  	pdes[0].config |= cpu_to_le32(SDXC_IDMAC_DES0_FD);