linux-kernel - Re: [PATCH V1 1/1] mmc: sdhci: fix DMA configure compatibility issue when 64bit DMA mode is used.

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Date:   Mon, 29 May 2023 18:00:18 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Chevron Li <chevron_li@....com>, ulf.hansson@...aro.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     shirley.her@...hubtech.com, xiaoguang.yu@...hubtech.com,
        shaper.liu@...hubtech.com, justin.wang@...hubtech.com,
        Chevron Li <chevron.li@...hubtech.com>
Subject: Re: [PATCH V1 1/1] mmc: sdhci: fix DMA configure compatibility issue
 when 64bit DMA mode is used.

On 23/05/23 14:11, Chevron Li wrote:
> From: Chevron Li <chevron.li@...hubtech.com>
> 
> Bayhub SD host has hardware limitation:
> 1.The upper 32bit address is inhibited to be written at SD Host Register
>   [03E][13]=0 (32bits addressing) mode, is admitted to be written only at
>   SD Host Register [03E][13]=1 (64bits addressing) mode.
> 2.Because of above item#1, need to configure SD Host Register [03E][13] to
>   1(64bits addressing mode) before set 64bit ADMA system address's higher
>   32bits SD Host Register [05F~05C] if 64 bits addressing mode is used.
> 
> The hardware limitation is reasonable for below reasons:
> 1.Normal flow should set DMA working mode first, then do
>   DMA-transfer-related configuration, such as system address.
> 2.The hardware limitation may avoid the software to configure wrong higher
>   32bit address at 32bits addressing mode although it is redundant.
> 
> The change that set 32bits/64bits addressing mode before set ADMA address,
>   has no side-effect to other host IPs for below reason:
> The setting order is reasonable and standard: DMA Mode setting first and
>   then DMA address setting. It meets all DMA setting sequence.
> 
> Signed-off-by: Chevron Li <chevron.li@...hubtech.com>

It should be OK.

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
> Change in V1:
> Set dma mode configure before set dma address
> ---
>  drivers/mmc/host/sdhci.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 3241916141d7..ff41aa56564e 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1167,6 +1167,8 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
>  		}
>  	}
>  
> +	sdhci_config_dma(host);
> +
>  	if (host->flags & SDHCI_REQ_USE_DMA) {
>  		int sg_cnt = sdhci_pre_dma_transfer(host, data, COOKIE_MAPPED);
>  
> @@ -1186,8 +1188,6 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
>  		}
>  	}
>  
> -	sdhci_config_dma(host);
> -
>  	if (!(host->flags & SDHCI_REQ_USE_DMA)) {
>  		int flags;
>  
> 
> base-commit: cc3c44c9fda264c6d401be04e95449a57c1231c6