imx233: add support for 50MHz clock with SD cards

Now that the drive strength problem has been fixed, we can safely
drive sd cards at 48MHz in HS mode to get the best possible
transfer speed at 3.3V.

Change-Id: I0291589c399fb4880deba97895ff578451a32f99

1 files changed, 25 insertions, 34 deletions

diff --git a/firmware/target/arm/imx233/sdmmc-imx233.c b/firmware/target/arm/imx233/sdmmc-imx233.c
index 164bf79..0d07822 100644
--- a/firmware/target/arm/imx233/sdmmc-imx233.c
+++ b/firmware/target/arm/imx233/sdmmc-imx233.c
@@ -316,7 +316,7 @@ static int init_sd_card(int drive)
     imx233_ssp_set_block_size(ssp, 9);
 
     SDMMC_RCA(drive) = 0;
-    bool sd_v2 = false;
+    bool sd_v2 = false, sd_hs = false;
     uint32_t resp;
     long init_timeout;
     /* go to idle state */
@@ -349,35 +349,6 @@ static int init_sd_card(int drive)
     if(!send_cmd(drive, SD_SEND_RELATIVE_ADDR, 0, MCI_RESP, &SDMMC_INFO(drive).rca))
         return -4;
 
-    /* Try to switch V2 cards to HS timings, non HS seem to ignore this */
-    if(sd_v2)
-    {
-        /*  CMD7 w/rca: Select card to put it in TRAN state */
-        if(!send_cmd(drive, SD_SELECT_CARD, SDMMC_RCA(drive), MCI_RESP, NULL))
-            return -5;
-
-        if(wait_for_state(drive, SD_TRAN))
-            return -6;
-
-        /* CMD6 */
-        {
-            /* only transfer 64 bytes */
-            imx233_ssp_set_block_size(ssp, /*log2(64)*/6);
-            if(imx233_ssp_sd_mmc_transfer(ssp, SD_SWITCH_FUNC, 0x80fffff1,
-                    SSP_SHORT_RESP, aligned_buffer[drive], 1, true, true, NULL))
-            {
-                imx233_ssp_set_block_size(ssp, /*log2(512)*/9);
-                return -12;
-            }
-            imx233_ssp_set_block_size(ssp, /*log2(512)*/9);
-        }
-
-        /*  go back to STBY state so we can read csd */
-        /*  CMD7 w/rca=0:  Deselect card to put it in STBY state */
-        if(!send_cmd(drive, SD_DESELECT_CARD, 0, MCI_NO_RESP, NULL))
-            return -8;
-    }
-
     /* CMD9 send CSD */
     if(!send_cmd(drive, SD_SEND_CSD, SDMMC_RCA(drive), MCI_RESP|MCI_LONG_RESP,
             SDMMC_INFO(drive).csd))
@@ -387,10 +358,6 @@ static int init_sd_card(int drive)
     window_start[drive] = 0;
     window_end[drive] = SDMMC_INFO(drive).numblocks;
 
-    /* SSPCLK @ 96MHz
-     * gives bitrate of 96 / 4 / 1 = 24MHz */
-    imx233_ssp_set_timings(ssp, 4, 0, 0xffff);
-
     /* CMD7 w/rca: Select card to put it in TRAN state */
     if(!send_cmd(drive, SD_SELECT_CARD, SDMMC_RCA(drive), MCI_RESP, &resp))
         return -12;
@@ -407,6 +374,22 @@ static int init_sd_card(int drive)
     /* Switch to 4-bit */
     imx233_ssp_set_bus_width(ssp, 4);
 
+    /* Try to switch V2 cards to HS timings, non HS seem to ignore this */
+    if(sd_v2)
+    {
+        /* CMD6 switch to HS */
+        {
+            /* only transfer 64 bytes */
+            imx233_ssp_set_block_size(ssp, /*log2(64)*/6);
+            if(imx233_ssp_sd_mmc_transfer(ssp, SD_SWITCH_FUNC, 0x80fffff1,
+                    SSP_SHORT_RESP, aligned_buffer[drive], 1, true, true, NULL))
+                return -12;
+            imx233_ssp_set_block_size(ssp, /*log2(512)*/9);
+            if((aligned_buffer[drive][16] & 0xf) == 1)
+                sd_hs = true;
+        }
+    }
+
     /* probe for CMD23 support */
     support_set_block_count[drive] = false;
     /* ACMD51, only transfer 8 bytes */
@@ -422,6 +405,14 @@ static int init_sd_card(int drive)
     }
     imx233_ssp_set_block_size(ssp, /*log2(512)*/9);
 
+    /* SSPCLK @ 96MHz
+     * gives bitrate of 96 / 4 / 1 = 24MHz
+     * gives bitrate of 96 / 2 / 1 = 48MHz */
+    if(sd_hs)
+        imx233_ssp_set_timings(ssp, 2, 0, 0xffff);
+    else
+        imx233_ssp_set_timings(ssp, 4, 0, 0xffff);
+
     SDMMC_INFO(drive).initialized = 1;
 
     return 0;