[PATCH] sd: SD 4-bit bus

Infrastructure for 4-bit bus transfers with SD cards.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 52 insertions, 0 deletions

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 21d4fb3314f8..6414f071a2a4 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -335,6 +335,40 @@ static int mmc_select_card(struct mmc_host *host, struct mmc_card *card)
         if (err != MMC_ERR_NONE)
                 return err;
 
+        /*
+         * Default bus width is 1 bit.
+         */
+        host->ios.bus_width = MMC_BUS_WIDTH_1;
+
+        /*
+         * We can only change the bus width of the selected
+         * card so therefore we have to put the handling
+         * here.
+         */
+        if (host->caps & MMC_CAP_4_BIT_DATA) {
+                /*
+                 * The card is in 1 bit mode by default so
+                 * we only need to change if it supports the
+                 * wider version.
+                 */
+                if (mmc_card_sd(card) &&
+                        (card->scr.bus_widths & SD_SCR_BUS_WIDTH_4)) {
+                        struct mmc_command cmd;
+                        cmd.opcode = SD_APP_SET_BUS_WIDTH;
+                        cmd.arg = SD_BUS_WIDTH_4;
+                        cmd.flags = MMC_RSP_R1;
+
+                        err = mmc_wait_for_app_cmd(host, card->rca, &cmd,
+                                CMD_RETRIES);
+                        if (err != MMC_ERR_NONE)
+                                return err;
+
+                        host->ios.bus_width = MMC_BUS_WIDTH_4;
+                }
+        }
+
+        host->ops->set_ios(host, &host->ios);
+
         return MMC_ERR_NONE;
 }
 
@@ -653,6 +687,7 @@ static void mmc_power_up(struct mmc_host *host)
         host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
         host->ios.chip_select = MMC_CS_DONTCARE;
         host->ios.power_mode = MMC_POWER_UP;
+        host->ios.bus_width = MMC_BUS_WIDTH_1;
         host->ops->set_ios(host, &host->ios);
 
         mmc_delay(1);
@@ -671,6 +706,7 @@ static void mmc_power_off(struct mmc_host *host)
         host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
         host->ios.chip_select = MMC_CS_DONTCARE;
         host->ios.power_mode = MMC_POWER_OFF;
+        host->ios.bus_width = MMC_BUS_WIDTH_1;
         host->ops->set_ios(host, &host->ios);
 }
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 8c5f71376e41..6014160d9c06 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -57,6 +57,11 @@ struct mmc_ios {
 #define MMC_POWER_OFF           0
 #define MMC_POWER_UP            1
 #define MMC_POWER_ON            2
+
+        unsigned char   bus_width;              /* data bus width */
+
+#define MMC_BUS_WIDTH_1         0
+#define MMC_BUS_WIDTH_4         2
 };
 
 struct mmc_host_ops {
@@ -77,6 +82,10 @@ struct mmc_host {
         unsigned int            f_max;
         u32                     ocr_avail;
 
+        unsigned long           caps;           /* Host capabilities */
+
+#define MMC_CAP_4_BIT_DATA      (1 << 0)        /* Can the host do 4 bit transfers */
+
         /* host specific block data */
         unsigned int            max_seg_size;   /* see blk_queue_max_segment_size */
         unsigned short          max_hw_segs;    /* see blk_queue_max_hw_segments */
diff --git a/include/linux/mmc/protocol.h b/include/linux/mmc/protocol.h
index 896342817b97..f819cae92266 100644
--- a/include/linux/mmc/protocol.h
+++ b/include/linux/mmc/protocol.h
@@ -236,5 +236,12 @@ struct _mmc_csd {
 #define CSD_SPEC_VER_2      2           /* Implements system specification 2.0 - 2.2 */
 #define CSD_SPEC_VER_3      3           /* Implements system specification 3.1 */
 
+
+/*
+ * SD bus widths
+ */
+#define SD_BUS_WIDTH_1      0
+#define SD_BUS_WIDTH_4      2
+
 #endif  /* MMC_MMC_PROTOCOL_H */