Re: [PATCH v4 2/3] mmc: sdhci: add quirks for be to le byte swapping

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

On 13/05/20 11:41 pm, Angelo Dureghello wrote:
> Some controller as the ColdFire eshdc may require an endianness
> byte swap, becouse DMA read endianness is not configurable.
> 
> Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
> ---
> Changes for v3:
> - add post request callback
> Changes for v4:
> none
> ---
>  drivers/mmc/host/sdhci.c | 7 +++++++
>  drivers/mmc/host/sdhci.h | 2 ++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 3f716466fcfd..d3bfbb6e11d5 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -637,6 +637,13 @@ static int sdhci_pre_dma_transfer(struct sdhci_host *host,
>  			sg_copy_to_buffer(data->sg, data->sg_len,
>  					  host->bounce_buffer,
>  					  length);
> +
> +			/*
> +			 * Endianness can't be swapped in the sg list,
> +			 * since the sg list is processed again later on.
> +			 */

The data in the sg list must not be changed because we don't know how
else it might be being used.  Maybe leave out the comment.

> +			if (host->ops->pre_dma_transfer)
> +				host->ops->pre_dma_transfer(host, data);

Let's make this slightly more generic i.e.

			if (host->ops->copy_to_bounce_buffer) {
				host->ops->copy_to_bounce_buffer(host, data);
			} else {
				sg_copy_to_buffer(data->sg, data->sg_len,
						  host->bounce_buffer,
						  length);
			}


>  		}
>  		/* Switch ownership to the DMA */
>  		dma_sync_single_for_device(host->mmc->parent,
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 79dffbb731d3..076054308423 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -653,6 +653,8 @@ struct sdhci_ops {
>  	void	(*voltage_switch)(struct sdhci_host *host);
>  	void	(*adma_write_desc)(struct sdhci_host *host, void **desc,
>  				   dma_addr_t addr, int len, unsigned int cmd);
> +	void	(*pre_dma_transfer)(struct sdhci_host *host,
> +				    struct mmc_data *data);
>  	void	(*request_done)(struct sdhci_host *host,
>  				struct mmc_request *mrq);
>  };
>