Hi,
On 5/11/26 2:08 PM, Sascha Hauer wrote:
> HS400ES bypasses HS200 tuning entirely: the eMMC drives a data strobe
> line which the controller samples on, so the read path doesn't need
> software-tuned phase. It still ends up in MMC_TIMING_MMC_HS400.
>
> Detection: a card advertises HS400ES via EXT_CSD_STROBE_SUPPORT[184],
> which sits outside DEVICE_TYPE; record it as a synthetic
> EXT_CSD_CARD_TYPE_HS400ES bit in mmc_avail_type when the host
> declares MMC_CAP2_HS400_ES (mmc-hs400-enhanced-strobe in DT) and the
> card has both STROBE_SUPPORT set and one of the HS400 voltage variants.
>
> Transition (mmc_select_hs400es):
> 1. Negotiate 8-bit bus in HS mode (HS400 needs 8-bit).
> 2. CMD6 EXT_CSD_HS_TIMING = HS, host to HS rate.
> 3. CMD6 EXT_CSD_BUS_WIDTH = 8-bit DDR | STROBE bit, so the card
> starts driving the strobe line.
> 4. CMD6 EXT_CSD_HS_TIMING = HS400, host to HS400 timing at
> hs200_max_dtr (200 MHz, DDR-sampled => 400 MT/s).
> 5. Call host->ops.hs400_enhanced_strobe so the controller enables
> enhanced strobe sampling.
>
> mmc_select_timing prefers HS400ES over HS200 + HS400; on any failure
> it clears the flag and falls back to HS200. mci_startup_mmc returns
> early when mmc_select_timing already landed us in HS400 (HS400ES has
> no follow-up tuning step).
>
> mci_ops gains an optional hs400_enhanced_strobe hook for the
> controller's enhanced-strobe enable.
>
> Assisted-by: Claude Opus 4.7 <[email protected]>
> Signed-off-by: Sascha Hauer <[email protected]>
> ---
> drivers/mci/mci-core.c | 108
> ++++++++++++++++++++++++++++++++++++++++++++++++-
> include/mci.h | 4 ++
> 2 files changed, 111 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
> index 58b28ec653..0cfddb8d43 100644
> --- a/drivers/mci/mci-core.c
> +++ b/drivers/mci/mci-core.c
> @@ -1798,6 +1798,16 @@ static void mmc_select_max_dtr(struct mci *mci)
> avail_type |= EXT_CSD_CARD_TYPE_HS400_1_2V;
> }
>
> + /*
> + * HS400ES capability is reported in EXT_CSD_STROBE_SUPPORT (byte 184),
> + * not in DEVICE_TYPE. Combine with one of the HS400 voltage variants;
> + * which voltage is used follows the same negotiation as HS400.
> + */
> + if ((caps2 & MMC_CAP2_HS400_ES) &&
> + mci->ext_csd[EXT_CSD_STROBE_SUPPORT] &&
Please add to mci_print_caps()
Also, please extend mci_timing_tostr() to return "HS400ES" for enhanced
strobe.
> + (avail_type & EXT_CSD_CARD_TYPE_HS400))
> + avail_type |= EXT_CSD_CARD_TYPE_HS400ES;
> +
> mci->host->hs200_max_dtr = hs200_max_dtr;
> mci->host->hs_max_dtr = hs_max_dtr;
> mci->host->mmc_avail_type = avail_type;
> @@ -1901,6 +1911,83 @@ static void mmc_set_bus_speed(struct mci *mci)
> mci_set_clock(mci, max_dtr);
> }
>
> +/*
> + * Switch directly to HS400 with Enhanced Strobe per JEDEC. Unlike plain
> + * HS400 this does not require HS200 tuning first - the controller samples
> + * data using the eMMC-driven strobe line. The transition is:
> + *
> + * 1. Negotiate 8-bit bus width in HS mode.
> + * 2. Switch the card to HS timing.
> + * 3. Set host to MMC_TIMING_MMC_HS at hs_max_dtr.
> + * 4. Switch card BUS_WIDTH to 8-bit DDR with the STROBE bit set, so
> + * the card drives the strobe line.
> + * 5. Switch the card to HS400 timing.
> + * 6. Switch the host to MMC_TIMING_MMC_HS400 and ramp the clock to
> + * hs200_max_dtr (200 MHz, DDR-sampled => 400 MT/s).
> + * 7. Tell the controller to enable enhanced strobe sampling.
> + */
> +static int mmc_select_hs400es(struct mci *mci)
> +{
> + struct mci_host *host = mci->host;
> + int err;
> + u8 val;
> +
> + /* Step 1: 8-bit bus is mandatory for HS400ES */
> + err = mci_mmc_try_bus_width(mci, MMC_BUS_WIDTH_8, MMC_TIMING_MMC_HS);
> + if (err < 0) {
> + dev_err(&mci->dev, "HS400ES requires 8-bit bus width\n");
> + return err;
> + }
> +
> + /* Step 2: switch card to HS timing */
> + err = mci_switch(mci, EXT_CSD_HS_TIMING, EXT_CSD_TIMING_HS);
> + if (err) {
> + dev_err(&mci->dev, "switch to HS for HS400ES failed: %d\n",
> err);
> + return err;
> + }
> +
> + /* Step 3: host follows to HS rate */
> + mci_set_timing(mci, MMC_TIMING_MMC_HS);
> + mci_set_clock(mci, host->hs_max_dtr);
> +
> + err = mci_switch_status(mci, true);
> + if (err)
> + return err;
> +
> + /* Step 4: 8-bit DDR with strobe enabled */
> + val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;
> + err = mci_switch(mci, EXT_CSD_BUS_WIDTH, val);
> + if (err) {
> + dev_err(&mci->dev, "switch to DDR8 with strobe failed: %d\n",
> err);
> + return err;
> + }
> +> + /* Step 5: switch card to HS400 */
> + val = EXT_CSD_TIMING_HS400 | (host->drive_strength <<
> EXT_CSD_DRV_STR_SHIFT);
The drive_strength is initialized by mmc_select_driver_type() and it
seems no one will have called it for HS400ES?
> + err = mci_switch(mci, EXT_CSD_HS_TIMING, val);
> + if (err) {
> + dev_err(&mci->dev, "switch to HS400 for HS400ES failed: %d\n",
> err);
> + return err;
> + }
> +
> + /* Step 6: host to HS400 timing and final clock */
> + mci_set_timing(mci, MMC_TIMING_MMC_HS400);
> + mmc_set_bus_speed(mci);
> +
> + err = mci_switch_status(mci, true);
> + if (err)
> + return err;
Should this not be _after_ the enhanced strobe setting, so we are able
to propagate an error on issues?
> +
> + /* Step 7: enable enhanced strobe in the controller */
> + host->ios.enhanced_strobe = true;
> + if (host->ops.hs400_enhanced_strobe)
> + host->ops.hs400_enhanced_strobe(host, &host->ios);
> +
> + dev_dbg(&mci->dev, "HS400ES selected\n");
> +
> + return 0;
> +}
> +
> /*
> * Activate HS200 or HS400ES mode if supported.
> */
> @@ -1910,6 +1997,20 @@ int mmc_select_timing(struct mci *mci)
>
> mmc_select_max_dtr(mci);
>
> + /*
> + * HS400ES is the preferred path when both card and host support it:
> + * it ends up in HS400 without needing HS200 tuning. If the transition
> + * fails for any reason, drop the flag and fall through to HS200/HS400.
> + */
> + if (mci->host->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400ES) {
> + err = mmc_select_hs400es(mci);
> + if (!err)
> + goto out;
> + dev_dbg(&mci->dev, "HS400ES failed (%d), trying HS200\n", err);
> + mci->host->mmc_avail_type &= ~EXT_CSD_CARD_TYPE_HS400ES;
> + err = 0;
> + }
> +
> if (mci->host->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200) {
> err = mmc_select_hs200(mci);
> if (err == -EBADMSG)
> @@ -2014,6 +2115,10 @@ static int mci_startup_mmc(struct mci *mci)
> if (ret)
> return ret;
>
> + /* HS400ES took us straight to HS400 without tuning. Done. */
> + if (mmc_card_hs400(mci))
> + return 0;
> +
> if (mmc_card_hs200(mci)) {
> ret = mmc_hs200_tuning(mci);
> if (!ret) {
> @@ -2698,7 +2803,8 @@ static void mci_info(struct device *dev)
> bw = 1;
>
> printf(" current buswidth: %d\n", bw);
> - printf(" current timing: %s\n", mci_timing_tostr(host->ios.timing));
> + printf(" current timing: %s%s\n", mci_timing_tostr(host->ios.timing),
> + host->ios.enhanced_strobe ? " (Enhanced Strobe)" : "");
I would just append an ES suffix.
> mci_print_caps(host->host_caps, host->caps2);
>
> printf("Card information:\n");
> diff --git a/include/mci.h b/include/mci.h
> index a7cd0c5ae2..7a86a80b03 100644
> --- a/include/mci.h
> +++ b/include/mci.h
> @@ -406,6 +406,7 @@
> #define EXT_CSD_DDR_BUS_WIDTH_4 5 /* Card is in 4 bit DDR mode */
> #define EXT_CSD_DDR_BUS_WIDTH_8 6 /* Card is in 8 bit DDR mode */
> #define EXT_CSD_DDR_FLAG BIT(2) /* Flag for DDR mode */
> +#define EXT_CSD_BUS_WIDTH_STROBE BIT(7) /* Enhanced strobe mode (HS400ES) */
>
> #define EXT_CSD_TIMING_BC 0 /* Backwards compatility */
> #define EXT_CSD_TIMING_HS 1 /* High speed */
> @@ -567,6 +568,7 @@ struct mci_ios {
> enum mci_bus_width bus_width; /* data bus width */
> enum mci_timing timing; /* timing specification
> used */
> unsigned char drv_type; /* driver type (A, B,
> C, D) */
> + bool enhanced_strobe; /* HS400ES selected */
> };
>
> struct mci;
> @@ -586,6 +588,8 @@ struct mci_ops {
> /* The tuning command opcode value is different for SD and eMMC cards */
> int (*execute_tuning)(struct mci_host *, u32);
> void (*set_uhs_signaling)(struct mci_host *host, unsigned int timing);
> + /* Enable enhanced strobe in the controller (HS400ES) */
> + void (*hs400_enhanced_strobe)(struct mci_host *, struct mci_ios *);
> };
>
> /** host information */
Cheers,
Ahmad
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