RE: [PATCH 1/3] mmc: omap_hsmmc: use packet sync'd DMA

["Madhusudhan" <madhu.cr@ti.com>]

> -----Original Message-----
> From: David Vrabel [mailto:david.vrabel@csr.com]
> Sent: Wednesday, February 10, 2010 5:52 AM
> To: linux-mmc@vger.kernel.org
> Cc: David Vrabel; linux-omap@vger.kernel.org; madhu.cr@ti.com
> Subject: [PATCH 1/3] mmc: omap_hsmmc: use packet sync'd DMA
> 
> Use packet sync'd DMA in the omap_hsmmc driver to avoid the
> restriction that transfers must be a multiple of the block size.  This
> is required for byte-mode transfers to SDIO cards.
> 
What is the typical scenario here? Is it IO_RW_EXTENDED with block_mode
turned off? 

> Signed-off-by: David Vrabel <david.vrabel@csr.com>
> ---
>  drivers/mmc/host/omap_hsmmc.c |   17 +++++------------
>  1 files changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index 4b23225..e7142a2 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -114,6 +114,7 @@
> 
>  #define MMC_TIMEOUT_MS		20
>  #define OMAP_MMC_MASTER_CLOCK	96000000
> +#define OMAP_HSMMC_FIFO_WORDS	(512/4)
>  #define DRIVER_NAME		"mmci-omap-hs"
> 
>  /* Timeouts for entering power saving states on inactivity, msec */
> @@ -887,12 +888,12 @@ static void omap_hsmmc_config_dma_params(struct
> omap_hsmmc_host *host,
>  	dma_ch = host->dma_ch;
>  	if (data->flags & MMC_DATA_WRITE) {
>  		omap_set_dma_dest_params(dma_ch, 0, OMAP_DMA_AMODE_CONSTANT,
> -			(host->mapbase + OMAP_HSMMC_DATA), 0, 0);
> +			(host->mapbase + OMAP_HSMMC_DATA), 0,
> OMAP_HSMMC_FIFO_WORDS);
>  		omap_set_dma_src_params(dma_ch, 0, OMAP_DMA_AMODE_POST_INC,
>  			sg_dma_address(sgl), 0, 0);
>  	} else {
>  		omap_set_dma_src_params(dma_ch, 0, OMAP_DMA_AMODE_CONSTANT,
> -			(host->mapbase + OMAP_HSMMC_DATA), 0, 0);
> +			(host->mapbase + OMAP_HSMMC_DATA), 0,
> OMAP_HSMMC_FIFO_WORDS);
>  		omap_set_dma_dest_params(dma_ch, 0, OMAP_DMA_AMODE_POST_INC,
>  			sg_dma_address(sgl), 0, 0);
>  	}
> @@ -901,7 +902,7 @@ static void omap_hsmmc_config_dma_params(struct
> omap_hsmmc_host *host,
>  	nblk = sg_dma_len(sgl) / blksz;
> 
>  	omap_set_dma_transfer_params(dma_ch, OMAP_DMA_DATA_TYPE_S32,
> -			blksz / 4, nblk, OMAP_DMA_SYNC_FRAME,
> +			blksz / 4, nblk, OMAP_DMA_SYNC_PACKET,
>  			omap_hsmmc_get_dma_sync_dev(host, data),
>  			!(data->flags & MMC_DATA_WRITE));
> 

How does this configuration help? Isn't the PACKET again a multiple of
blksz?
 
> @@ -944,17 +945,9 @@ static void omap_hsmmc_dma_cb(int lch, u16 ch_status,
> void *data)
>  static int omap_hsmmc_start_dma_transfer(struct omap_hsmmc_host *host,
>  					struct mmc_request *req)
>  {
> -	int dma_ch = 0, ret = 0, err = 1, i;
> +	int dma_ch = 0, ret = 0, err = 1;
>  	struct mmc_data *data = req->data;
> 
> -	/* Sanity check: all the SG entries must be aligned by block size.
> */
> -	for (i = 0; i < data->sg_len; i++) {
> -		struct scatterlist *sgl;
> -
> -		sgl = data->sg + i;
> -		if (sgl->length % data->blksz)
> -			return -EINVAL;
> -	}
>  	if ((data->blksz % 4) != 0)
>  		/* REVISIT: The MMC buffer increments only when MSB is
> written.
>  		 * Return error for blksz which is non multiple of four.
> --
> 1.6.3.3