mmc: core: Don't try UHS-I mode if 4-bit mode isn't supported

Per SD specification physical layer v4.0, section 3.9.4, it
says "UHS-I supports only 4-bit mode. Host shall select 4-bit
mode by ACMD6. However mmc_sd_init_uhs_card() still go ahead
to initialize the cards anyway, whether card or host won't
support 4-bit mode.

  This breaks the platforms which could support UHS-I mode but on
some certain boards only support 1-bit mode with a UHS-I card inserted,
as all the tuning process is broken due to this. Alternatively, we
should check the return value from mmc_set_bus_width() to see if host
could finish the request to switch the bus width on its side. But that
needs more thing to do than this patch that just bails out early to try
high speed mode if 4-bit mode isn't available for whatever reason. And
this patch could also fix the same problem for sdio since R4_18V_PRESENT
won't be set for ocr when mmc_sdio_init_card() finds mmc_host_uhs()
is false.

  Note that this patch doesn't keep the checking of card->scr.sda_spec3
and comparing card->scr.bus_widths with SD_SCR_BUS_WIDTH_4 within
mmc_sd_init_uhs_card() since if the sd cards response with SD_ROCR_S18A,
it definitely supports UHS-I mode, which implicitly means these checkings
are always true.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
index 06ec19b..4805438 100644 (file)
--- a/drivers/mmc/core/host.h
+++ b/drivers/mmc/core/host.h
@@ -56,7 +56,8 @@ static inline int mmc_host_uhs(struct mmc_host *host)
        return host->caps &
                (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
                 MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 |
-                MMC_CAP_UHS_DDR50);
+                MMC_CAP_UHS_DDR50) &&
+              host->caps & MMC_CAP_4_BIT_DATA;
 }
 
 static inline bool mmc_card_hs200(struct mmc_card *card)

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 62b84dd..d094497 100644 (file)
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -582,9 +582,6 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
        int err;
        u8 *status;
 
-       if (!card->scr.sda_spec3)
-               return 0;
-
        if (!(card->csd.cmdclass & CCC_SWITCH))
                return 0;
 
@@ -593,14 +590,11 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
                return -ENOMEM;
 
        /* Set 4-bit bus width */
-       if ((card->host->caps & MMC_CAP_4_BIT_DATA) &&
-           (card->scr.bus_widths & SD_SCR_BUS_WIDTH_4)) {
-               err = mmc_app_set_bus_width(card, MMC_BUS_WIDTH_4);
-               if (err)
-                       goto out;
+       err = mmc_app_set_bus_width(card, MMC_BUS_WIDTH_4);
+       if (err)
+               goto out;
 
-               mmc_set_bus_width(card->host, MMC_BUS_WIDTH_4);
-       }
+       mmc_set_bus_width(card->host, MMC_BUS_WIDTH_4);
 
        /*
         * Select the bus speed mode depending on host
@@ -1033,7 +1027,7 @@ retry:
        }
 
        /* Initialization sequence for UHS-I cards */
-       if (rocr & SD_ROCR_S18A) {
+       if (rocr & SD_ROCR_S18A && mmc_host_uhs(host)) {
                err = mmc_sd_init_uhs_card(card);
                if (err)
                        goto free_card;