[U-Boot] [RFC] mmc: add setdsr support

[Pantelis Antoniou]

Hi Markus,

On Dec 16, 2013, at 1:57 PM, Markus Niebel wrote:

> From: Markus Niebel <Markus.Niebel at tqs.de>
> 
> The eMMC and the SD-Card specifications describe the optional SET_DSR command.
> During measurements at our lab we found that some cards implementing this feature
> having really strong driver strengts per default. This can lead to voltage peaks
> above the specification of the host on signal edges for data sent from a card to 
> the host.
> 
> Since availability of a given card type may be shorter than the time a certain
> hardware will be produced it is useful to have support for this command (Alternative
> would be changing termination resistors and adapting the driver strength of the 
> host to the used card.)
> 
> Following proposal for an implementation:
> 
> - new field that reflects CSD field DSR_IMP in struct mmc
> - new field for design specific DSR value in struct mmc
> - board code can set DSR value in mmc struct just after registering an controller
> - mmc_startup sends the the stored DSR value before selecting a card, if DSR_IMP is set
> 
> Additionally the mmc command is extended to make is possible to play around with different DSR values.
> 
> Signed-off-by: Markus Niebel <Markus.Niebel at tqs.de>
> 

In general looks good. Please add a line describing which platform/board this pertains to, and
example setting the signal strength.

> 
> ---
> common/cmd_mmc.c  |   23 +++++++++++++++++++++++
> drivers/mmc/mmc.c |   18 ++++++++++++++++++
> include/mmc.h     |    3 +++
> 3 files changed, 44 insertions(+)
> 
> diff --git a/common/cmd_mmc.c b/common/cmd_mmc.c
> index 67a94a7..da5fef9 100644
> --- a/common/cmd_mmc.c
> +++ b/common/cmd_mmc.c
> @@ -340,6 +340,28 @@ static int do_mmcops(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
> 		}
> #endif /* CONFIG_SUPPORT_EMMC_BOOT */
> 	}
> +
> +	else if (argc == 3 && strcmp(argv[1], "setdsr") == 0) {
> +		struct mmc *mmc = find_mmc_device(curr_device);
> +		u32 val = simple_strtoul(argv[2], NULL, 16);
> +		int ret;
> +
> +		if (!mmc) {
> +			printf("no mmc device at slot %x\n", curr_device);
> +			return 1;
> +		}
> +		ret = mmc_set_dsr(mmc, val);
> +		printf("set dsr %s\n", (!ret) ? "OK, force rescan" : "ERROR");
> +		if (!ret) {
> +			mmc->has_init = 0;
> +			if (mmc_init(mmc))
> +				return 1;
> +			else
> +				return 0;
> +		}
> +		return ret;
> +	}
> +
> 	state = MMC_INVALID;
> 	if (argc == 5 && strcmp(argv[1], "read") == 0)
> 		state = MMC_READ;
> @@ -423,5 +445,6 @@ U_BOOT_CMD(
> 	"mmc bootpart <device num> <boot part size MB> <RPMB part size MB>\n"
> 	" - change sizes of boot and RPMB partitions of specified device\n"
> #endif
> +	"mmc setdsr - set DSR register value\n"
> 	);
> #endif /* !CONFIG_GENERIC_MMC */
> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
> index e1461a9..c6a1c23 100644
> --- a/drivers/mmc/mmc.c
> +++ b/drivers/mmc/mmc.c
> @@ -877,6 +877,7 @@ static int mmc_startup(struct mmc *mmc)
> 
> 	mmc->tran_speed = freq * mult;
> 
> +	mmc->dsr_imp = ((cmd.response[1] >> 12) & 0x1);
> 	mmc->read_bl_len = 1 << ((cmd.response[1] >> 16) & 0xf);
> 

^ stray new line

> 	if (IS_SD(mmc))
> @@ -907,6 +908,14 @@ static int mmc_startup(struct mmc *mmc)
> 	if (mmc->write_bl_len > MMC_MAX_BLOCK_LEN)
> 		mmc->write_bl_len = MMC_MAX_BLOCK_LEN;
> 
> +	if ((mmc->dsr_imp) && (0xffffffff != mmc->dsr)) {

^ weird formatting for the if, change to:

	  if (mmc->dsr_imp && mmc->dsr != 0xffffffff) {

> +		cmd.cmdidx = MMC_CMD_SET_DSR;
> +		cmd.cmdarg = (mmc->dsr & 0xffff) << 16;
> +		cmd.resp_type = MMC_RSP_NONE;
> +		if (mmc_send_cmd(mmc, &cmd, NULL))
> +			printf("MMC: SET_DSR failed\n");
> +	}
> +
> 	/* Select the card, and put it into Transfer Mode */
> 	if (!mmc_host_is_spi(mmc)) { /* cmd not supported in spi */
> 		cmd.cmdidx = MMC_CMD_SELECT_CARD;
> @@ -1163,6 +1172,9 @@ static int mmc_send_if_cond(struct mmc *mmc)
> 
> int mmc_register(struct mmc *mmc)
> {
> +	/* Setup dsr related values */
> +	mmc->dsr_imp = 0;
> +	mmc->dsr = 0xffffffff;
> 	/* Setup the universal parts of the block interface just once */
> 	mmc->block_dev.if_type = IF_TYPE_MMC;
> 	mmc->block_dev.dev = cur_dev_num++;
> @@ -1280,6 +1292,12 @@ int mmc_init(struct mmc *mmc)
> 	return err;
> }
> 
> +int mmc_set_dsr(struct mmc *mmc, u16 val)
> +{
> +	mmc->dsr = val;
> +	return 0;
> +}
> +
> /*
>  * CPU and board-specific MMC initializations.  Aliased function
>  * signals caller to move on
> diff --git a/include/mmc.h b/include/mmc.h
> index cb558da..facb819 100644
> --- a/include/mmc.h
> +++ b/include/mmc.h
> @@ -262,6 +262,8 @@ struct mmc {
> 	uint card_caps;
> 	uint host_caps;
> 	uint ocr;
> +	uint dsr;
> +	uint dsr_imp;
> 	uint scr[2];
> 	uint csd[4];
> 	uint cid[4];
> @@ -304,6 +306,7 @@ int board_mmc_getcd(struct mmc *mmc);
> int mmc_switch_part(int dev_num, unsigned int part_num);
> int mmc_getcd(struct mmc *mmc);
> int mmc_getwp(struct mmc *mmc);
> +int mmc_set_dsr(struct mmc *mmc, u16 val);
> void spl_mmc_load(void) __noreturn;
> /* Function to change the size of boot partition and rpmb partitions */
> int mmc_boot_partition_size_change(struct mmc *mmc, unsigned long bootsize,
> -- 
> 1.7.9.5
> 

Regards

-- Pantelis