mmc: core: eMMC bus width may not work on all platforms

CMD19 -- The offical way to validate bus widths from the JEDEC spec
does not work on all platforms.  Some platforms that use PCI/PCIe
to connect their SD controllers are known to fail.

If the quirk MMC_BUS_WIDTH_TEST is not defined we try to figure out
the bus width by reading the ext_csd at different bus widths and
compare this against the ext_csd read in 1 bit mode.  If no ext_csd
is available we default to 1 bit operations.

Code has been tested on mmp2 against 8 bit eMMC and Transcend 2GB
card that is known to not work in 4 bit mode.  The physical pins
on the card are not present to support 4 bit operation.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 0433fe66cbad59210c1254a28717a21a40a2d4f9..2a7e43bc796dfd1e798ad60a1ae6d0e7b98278a2 100644 (file)
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -174,14 +174,17 @@ static int mmc_decode_csd(struct mmc_card *card)
 }
 
 /*
- * Read and decode extended CSD.
+ * Read extended CSD.
  */
-static int mmc_read_ext_csd(struct mmc_card *card)
+static int mmc_get_ext_csd(struct mmc_card *card, u8 **new_ext_csd)
 {
        int err;
        u8 *ext_csd;
 
        BUG_ON(!card);
+       BUG_ON(!new_ext_csd);
+
+       *new_ext_csd = NULL;
 
        if (card->csd.mmca_vsn < CSD_SPEC_VER_4)
                return 0;
@@ -199,12 +202,15 @@ static int mmc_read_ext_csd(struct mmc_card *card)
 
        err = mmc_send_ext_csd(card, ext_csd);
        if (err) {
+               kfree(ext_csd);
+               *new_ext_csd = NULL;
+
                /* If the host or the card can't do the switch,
                 * fail more gracefully. */
                if ((err != -EINVAL)
                 && (err != -ENOSYS)
                 && (err != -EFAULT))
-                       goto out;
+                       return err;
 
                /*
                 * High capacity cards should have this "magic" size
@@ -222,9 +228,23 @@ static int mmc_read_ext_csd(struct mmc_card *card)
                                mmc_hostname(card->host));
                        err = 0;
                }
+       } else
+               *new_ext_csd = ext_csd;
 
-               goto out;
-       }
+       return err;
+}
+
+/*
+ * Decode extended CSD.
+ */
+static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
+{
+       int err = 0;
+
+       BUG_ON(!card);
+
+       if (!ext_csd)
+               return 0;
 
        /* Version is coded in the CSD_STRUCTURE byte in the EXT_CSD register */
        if (card->csd.structure == 3) {
@@ -372,8 +392,69 @@ static int mmc_read_ext_csd(struct mmc_card *card)
                card->erased_byte = 0x0;
 
 out:
+       return err;
+}
+
+static inline void mmc_free_ext_csd(u8 *ext_csd)
+{
        kfree(ext_csd);
+}
+
 
+static int mmc_compare_ext_csds(struct mmc_card *card, u8 *ext_csd,
+                       unsigned bus_width)
+{
+       u8 *bw_ext_csd;
+       int err;
+
+       err = mmc_get_ext_csd(card, &bw_ext_csd);
+       if (err)
+               return err;
+
+       if ((ext_csd == NULL || bw_ext_csd == NULL)) {
+               if (bus_width != MMC_BUS_WIDTH_1)
+                       err = -EINVAL;
+               goto out;
+       }
+
+       if (bus_width == MMC_BUS_WIDTH_1)
+               goto out;
+
+       /* only compare read only fields */
+       err = (!(ext_csd[EXT_CSD_PARTITION_SUPPORT] ==
+                       bw_ext_csd[EXT_CSD_PARTITION_SUPPORT]) &&
+               (ext_csd[EXT_CSD_ERASED_MEM_CONT] ==
+                       bw_ext_csd[EXT_CSD_ERASED_MEM_CONT]) &&
+               (ext_csd[EXT_CSD_REV] ==
+                       bw_ext_csd[EXT_CSD_REV]) &&
+               (ext_csd[EXT_CSD_STRUCTURE] ==
+                       bw_ext_csd[EXT_CSD_STRUCTURE]) &&
+               (ext_csd[EXT_CSD_CARD_TYPE] ==
+                       bw_ext_csd[EXT_CSD_CARD_TYPE]) &&
+               (ext_csd[EXT_CSD_S_A_TIMEOUT] ==
+                       bw_ext_csd[EXT_CSD_S_A_TIMEOUT]) &&
+               (ext_csd[EXT_CSD_HC_WP_GRP_SIZE] ==
+                       bw_ext_csd[EXT_CSD_HC_WP_GRP_SIZE]) &&
+               (ext_csd[EXT_CSD_ERASE_TIMEOUT_MULT] ==
+                       bw_ext_csd[EXT_CSD_ERASE_TIMEOUT_MULT]) &&
+               (ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] ==
+                       bw_ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE]) &&
+               (ext_csd[EXT_CSD_SEC_TRIM_MULT] ==
+                       bw_ext_csd[EXT_CSD_SEC_TRIM_MULT]) &&
+               (ext_csd[EXT_CSD_SEC_ERASE_MULT] ==
+                       bw_ext_csd[EXT_CSD_SEC_ERASE_MULT]) &&
+               (ext_csd[EXT_CSD_SEC_FEATURE_SUPPORT] ==
+                       bw_ext_csd[EXT_CSD_SEC_FEATURE_SUPPORT]) &&
+               (ext_csd[EXT_CSD_TRIM_MULT] ==
+                       bw_ext_csd[EXT_CSD_TRIM_MULT]) &&
+               memcmp(&ext_csd[EXT_CSD_SEC_CNT],
+                      &bw_ext_csd[EXT_CSD_SEC_CNT],
+                      4) != 0);
+       if (err)
+               err = -EINVAL;
+
+out:
+       mmc_free_ext_csd(bw_ext_csd);
        return err;
 }
 
@@ -438,6 +519,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
        u32 cid[4];
        unsigned int max_dtr;
        u32 rocr;
+       u8 *ext_csd = NULL;
 
        BUG_ON(!host);
        WARN_ON(!host->claimed);
@@ -536,7 +618,11 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
                /*
                 * Fetch and process extended CSD.
                 */
-               err = mmc_read_ext_csd(card);
+
+               err = mmc_get_ext_csd(card, &ext_csd);
+               if (err)
+                       goto free_card;
+               err = mmc_read_ext_csd(card, ext_csd);
                if (err)
                        goto free_card;
 
@@ -676,14 +762,18 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
                                         0);
                        if (!err) {
                                mmc_set_bus_width(card->host, bus_width);
+
                                /*
                                 * If controller can't handle bus width test,
-                                * use the highest bus width to maintain
-                                * compatibility with previous MMC behavior.
+                                * compare ext_csd previously read in 1 bit mode
+                                * against ext_csd at new bus width
                                 */
                                if (!(host->caps & MMC_CAP_BUS_WIDTH_TEST))
-                                       break;
-                               err = mmc_bus_test(card, bus_width);
+                                       err = mmc_compare_ext_csds(card,
+                                               ext_csd,
+                                               bus_width);
+                               else
+                                       err = mmc_bus_test(card, bus_width);
                                if (!err)
                                        break;
                        }
@@ -730,12 +820,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
        if (!oldcard)
                host->card = card;
 
+       mmc_free_ext_csd(ext_csd);
        return 0;
 
 free_card:
        if (!oldcard)
                mmc_remove_card(card);
 err:
+       mmc_free_ext_csd(ext_csd);
 
        return err;
 }