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SubjectRe: [PATCH v2] mmc: sdhci-cadence: tune multi-block read gap
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On 17/12/19 2:11 pm, Vladimir Kondratiev wrote:
> Additional tuning required for multi-block read command.
> Implement it accordingly to Cadence recommendation.
>
> 2 registers used: HRS37 and HRS38. To HRS37, SD interface mode programmed,
> this selects HRS38 slot - there is separate slot for every SD interface
> mode. HRS38 contains gap parameter,
> it is selected by starting with gap=0 and sending multi-block read command.
> gap incremented until multi-block read succeeds.
>
> As of now, this tuning executed for HS200 only
>
> Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@intel.com>
> ---
> drivers/mmc/host/sdhci-cadence.c | 137 ++++++++++++++++++++++++++++++-
> 1 file changed, 136 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
> index ae0ec27dd7cc..d0bed1932b6c 100644
> --- a/drivers/mmc/host/sdhci-cadence.c
> +++ b/drivers/mmc/host/sdhci-cadence.c
> @@ -34,6 +34,23 @@
> #define SDHCI_CDNS_HRS06_MODE_MMC_HS400 0x5
> #define SDHCI_CDNS_HRS06_MODE_MMC_HS400ES 0x6
>
> +/* Read block gap */
> +#define SDHCI_CDNS_HRS37 0x94 /* interface mode select */
> +#define SDHCI_CDNS_HRS37_MODE_DS 0x0
> +#define SDHCI_CDNS_HRS37_MODE_HS 0x1
> +#define SDHCI_CDNS_HRS37_MODE_UDS_SDR12 0x8
> +#define SDHCI_CDNS_HRS37_MODE_UDS_SDR25 0x9
> +#define SDHCI_CDNS_HRS37_MODE_UDS_SDR50 0xa
> +#define SDHCI_CDNS_HRS37_MODE_UDS_SDR104 0xb
> +#define SDHCI_CDNS_HRS37_MODE_UDS_DDR50 0xc
> +#define SDHCI_CDNS_HRS37_MODE_MMC_LEGACY 0x20
> +#define SDHCI_CDNS_HRS37_MODE_MMC_SDR 0x21
> +#define SDHCI_CDNS_HRS37_MODE_MMC_DDR 0x22
> +#define SDHCI_CDNS_HRS37_MODE_MMC_HS200 0x23
> +#define SDHCI_CDNS_HRS37_MODE_MMC_HS400 0x24
> +#define SDHCI_CDNS_HRS37_MODE_MMC_HS400ES 0x25
> +#define SDHCI_CDNS_HRS38 0x98 /* Read block gap coefficient */
> +#define SDHCI_CDNS_HRS38_BLKGAP_MAX 0xf
> /* SRS - Slot Register Set (SDHCI-compatible) */
> #define SDHCI_CDNS_SRS_BASE 0x200
>
> @@ -272,6 +289,118 @@ static int sdhci_cdns_set_tune_val(struct sdhci_host *host, unsigned int val)
> return 0;
> }
>
> +/**
> + * mmc_send_mb_read() - send multi-block read command
> + * @host: MMC host
> + *
> + * Sends multi-block read command, CMD23/CMD18/CMD12, ignore read data
> + *
> + * Return: error code
> + */
> +static int mmc_send_mb_read(struct mmc_host *host)
> +{
> + const int blksz = 512;
> + const int blocks = 32;
> + struct scatterlist sg;
> + struct mmc_command sbc = {
> + .opcode = MMC_SET_BLOCK_COUNT,
> + .arg = blocks,
> + .flags = MMC_RSP_R1 | MMC_CMD_AC,
> + };
> + struct mmc_command cmd = {
> + .opcode = MMC_READ_MULTIPLE_BLOCK,
> + .arg = 0,
> + .flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC,
> + };
> + struct mmc_command stop = {
> + .opcode = MMC_STOP_TRANSMISSION,
> + .arg = 0,
> + .flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC,
> + };
> + struct mmc_data data = {
> + .flags = MMC_DATA_READ,
> + .blksz = blksz,
> + .blocks = blocks,
> + .blk_addr = 0,
> + .timeout_ns = 800000000, /* 800ms */
> + .timeout_clks = 1000,
> + .sg = &sg,
> + .sg_len = 1,
> + };
> + struct mmc_request mrq = {
> + .sbc = &sbc,
> + .cmd = &cmd,
> + .data = &data,
> + .stop = &stop,
> + };
> + int size = blksz * blocks, err = 0;
> + u8 *data_buf;
> +
> + data_buf = kzalloc(size, GFP_KERNEL);
> + if (!data_buf)
> + return -ENOMEM;
> +
> + sg_init_one(&sg, data_buf, size);
> +
> + mmc_wait_for_req(host, &mrq);

This is a bit weird. Why can't a regular tuning command be used?

> +
> + if (cmd.error) {
> + err = cmd.error;
> + goto out;
> + }
> +
> + if (data.error) {
> + err = data.error;
> + goto out;
> + }
> +
> +out:
> + kfree(data_buf);
> + return err;
> +}
> +
> +/**
> + * sdhci_cdns_tune_blkgap() - tune multi-block read gap
> + * @mmc: MMC host
> + *
> + * Tune delay used in multi block read. To do so,
> + * try sending multi-block read command with incremented gap, unless
> + * it succeeds.
> + *
> + * Return: error code
> + */
> +static int sdhci_cdns_tune_blkgap(struct mmc_host *mmc)
> +{
> + struct sdhci_host *host = mmc_priv(mmc);
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct sdhci_cdns_priv *priv = sdhci_pltfm_priv(pltfm_host);
> + void __iomem *hrs37_reg = priv->hrs_addr + SDHCI_CDNS_HRS37;
> + void __iomem *hrs38_reg = priv->hrs_addr + SDHCI_CDNS_HRS38;
> + bool tuned = false;
> + u8 gap;
> + u8 hrs37_mode;
> +
> + switch (host->timing) {
> + case MMC_TIMING_MMC_HS200:
> + hrs37_mode = SDHCI_CDNS_HRS37_MODE_MMC_HS200;
> + break;
> + default:
> + return 0; /* no tuning in this mode */
> + }
> +
> + writel(hrs37_mode, hrs37_reg);
> +
> + for (gap = 0; gap <= SDHCI_CDNS_HRS38_BLKGAP_MAX; gap++) {
> + writel(gap, hrs38_reg);
> + tuned = !mmc_send_mb_read(mmc);
> + if (tuned)
> + break;
> + }
> + dev_dbg(mmc_dev(mmc), "read block gap tune %s, gap %d\n",
> + tuned ? "OK" : "failed", gap);
> + return tuned ? 0 : -EIO;
> +}
> +
> static int sdhci_cdns_execute_tuning(struct mmc_host *mmc, u32 opcode)
> {
> struct sdhci_host *host = mmc_priv(mmc);
> @@ -279,6 +408,7 @@ static int sdhci_cdns_execute_tuning(struct mmc_host *mmc, u32 opcode)
> int max_streak = 0;
> int end_of_streak = 0;
> int i;
> + int ret;
>
> /*
> * This handler only implements the eMMC tuning that is specific to
> @@ -308,7 +438,12 @@ static int sdhci_cdns_execute_tuning(struct mmc_host *mmc, u32 opcode)
> return -EIO;
> }
>
> - return sdhci_cdns_set_tune_val(host, end_of_streak - max_streak / 2);
> + ret = sdhci_cdns_set_tune_val(host, end_of_streak - max_streak / 2);
> +
> + if (!ret)
> + ret = sdhci_cdns_tune_blkgap(mmc);
> +
> + return ret;
> }
>
> static void sdhci_cdns_hs400_enhanced_strobe(struct mmc_host *mmc,
>

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