[U-Boot] [PATCH] i.MX28: Allow coexistence of PIO and DMA mode for SD/MMC

[Stefano Babic <sbabic@denx.de>]

On 05/04/2012 12:24, Marek Vasut wrote:
> This SD DMA function of i.MX28 is still apparently too experimental to be
> enabled by default in 2012.04 release. Enable this feature only if the user
> plans to tinker with DCache or explicitly enables it.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Stefano Babic <sbabic@denx.de>
> Cc: Wolfgang Denk <wd@denx.de>
> Cc: Detlev Zundel <dzu@denx.de>
> Cc: Fabio Estevam <fabio.estevam@freescale.com>
> ---

Hi Marek,

>  drivers/mmc/mxsmmc.c |   41 ++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 40 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/mmc/mxsmmc.c b/drivers/mmc/mxsmmc.c
> index e8bad9d..7187796 100644
> --- a/drivers/mmc/mxsmmc.c
> +++ b/drivers/mmc/mxsmmc.c
> @@ -66,8 +66,13 @@ mxsmmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
>  	struct mx28_ssp_regs *ssp_regs = priv->regs;
>  	uint32_t reg;
>  	int timeout;
> -	uint32_t data_count, cache_data_count;
> +	uint32_t data_count;
>  	uint32_t ctrl0;
> +#ifndef CONFIG_MXS_MMC_DMA
> +	uint32_t *data_ptr;
> +#else
> +	uint32_t cache_data_count;
> +#endif
>  
>  	debug("MMC%d: CMD%d\n", mmc->block_dev.dev, cmd->cmdidx);
>  
> @@ -185,7 +190,9 @@ mxsmmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
>  		return 0;
>  
>  	data_count = data->blocksize * data->blocks;
> +	timeout = MXSMMC_MAX_TIMEOUT;
>  
> +#ifdef CONFIG_MXS_MMC_DMA
>  	if (data_count % ARCH_DMA_MINALIGN)
>  		cache_data_count = roundup(data_count, ARCH_DMA_MINALIGN);
>  	else
> @@ -218,6 +225,38 @@ mxsmmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
>  		invalidate_dcache_range((uint32_t)priv->desc->cmd.address,
>  			(uint32_t)(priv->desc->cmd.address + cache_data_count));
>  	}
> +#else
> +	if (data->flags & MMC_DATA_READ) {
> +		data_ptr = (uint32_t *)data->dest;
> +		while (data_count && --timeout) {
> +			reg = readl(&ssp_regs->hw_ssp_status);
> +			if (!(reg & SSP_STATUS_FIFO_EMPTY)) {
> +				*data_ptr++ = readl(&ssp_regs->hw_ssp_data);
> +				data_count -= 4;
> +				timeout = MXSMMC_MAX_TIMEOUT;
> +			} else
> +				udelay(1000);
> +		}
> +	} else {
> +		data_ptr = (uint32_t *)data->src;
> +		timeout *= 100;
> +		while (data_count && --timeout) {
> +			reg = readl(&ssp_regs->hw_ssp_status);
> +			if (!(reg & SSP_STATUS_FIFO_FULL)) {
> +				writel(*data_ptr++, &ssp_regs->hw_ssp_data);
> +				data_count -= 4;
> +				timeout = MXSMMC_MAX_TIMEOUT;
> +			} else
> +				udelay(1000);
> +		}
> +	}

Ok, I see. This patch reverts to the status before applying the DMA's patch.
I would only ask if it makes sense to leave DMA support on MMC when we
know that is buggy. Is it DMA support working for NAND ? If yes, it is
not possible to enable DMA for NAND and disable it for MMC, as both
driver use the same CONFIG_MXS_MMC_DMA.

Anyway, I am not saying we should introduce a new switch, but maybe we
should drop DMA support in msx_mmc for this release avoiding confusion.
The current status with DMA support can be re-enabled on a -next branch.

Any thoughts ?

Best regards,
Stefano Babic

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