Re: [PATCH v2 8/9] mmc: sdhci-esdhc-mcf: Use sg_miter for swapping

[Adrian Hunter <adrian.hunter@intel.com>]

On 27/01/24 02:19, Linus Walleij wrote:
> Use sg_miter iterator instead of sg_virt() and custom code
> to loop over the scatterlist. The memory iterator will do
> bounce buffering if the page happens to be located in high memory,
> which the driver may or may not be using.
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Link: https://lore.kernel.org/linux-mmc/20240122073423.GA25859@lst.de/
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/mmc/host/sdhci-esdhc-mcf.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-mcf.c b/drivers/mmc/host/sdhci-esdhc-mcf.c
> index a07f8333cd6b..1909a11fd065 100644
> --- a/drivers/mmc/host/sdhci-esdhc-mcf.c
> +++ b/drivers/mmc/host/sdhci-esdhc-mcf.c
> @@ -299,9 +299,8 @@ static void esdhc_mcf_pltfm_set_bus_width(struct sdhci_host *host, int width)
>  static void esdhc_mcf_request_done(struct sdhci_host *host,
>  				   struct mmc_request *mrq)
>  {
> -	struct scatterlist *sg;
> +	struct sg_mapping_iter sgm;
>  	u32 *buffer;
> -	int i;
>  
>  	if (!mrq->data || !mrq->data->bytes_xfered)
>  		goto exit_done;
> @@ -313,10 +312,13 @@ static void esdhc_mcf_request_done(struct sdhci_host *host,
>  	 * On mcf5441x there is no hw sdma option/flag to select the dma
>  	 * transfer endiannes. A swap after the transfer is needed.
>  	 */
> -	for_each_sg(mrq->data->sg, sg, mrq->data->sg_len, i) {
> -		buffer = (u32 *)sg_virt(sg);
> -		esdhc_mcf_buffer_swap32(buffer, sg->length);
> +	sg_miter_start(&sgm, mrq->data->sg, mrq->data->sg_len,
> +		       SG_MITER_TO_SG | SG_MITER_FROM_SG);

Could be called from atomic context, so probably needs
SG_MITER_ATOMIC

> +	while (sg_miter_next(&sgm)) {
> +		buffer = sgm.addr;
> +		esdhc_mcf_buffer_swap32(buffer, sgm.length);
>  	}
> +	sg_miter_stop(&sgm);
>  
>  exit_done:
>  	mmc_request_done(host->mmc, mrq);
>