mmc: Support for high speed SD cards

Modern SD cards support a clock speed of 50 MHz. Make sure we test for
this capability and do the song and dance required to activate it.

Activating high speed support actually modifies the TRAN_SPEED field
of the CSD. But as the spec says that the cards must report 50 MHz,
we might as well skip re-reading the CSD.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/mmc.c

@@ -1157,6 +1157,116 @@ static void mmc_read_scrs(struct mmc_host *host)
 	mmc_deselect_cards(host);
 }
 
+static void mmc_read_switch_caps(struct mmc_host *host)
+{
+	int err;
+	struct mmc_card *card;
+	struct mmc_request mrq;
+	struct mmc_command cmd;
+	struct mmc_data data;
+	unsigned char *status;
+	struct scatterlist sg;
+
+	status = kmalloc(64, GFP_KERNEL);
+	if (!status) {
+		printk(KERN_WARNING "%s: Unable to allocate buffer for "
+			"reading switch capabilities.\n",
+			mmc_hostname(host));
+		return;
+	}
+
+	list_for_each_entry(card, &host->cards, node) {
+		if (card->state & (MMC_STATE_DEAD|MMC_STATE_PRESENT))
+			continue;
+		if (!mmc_card_sd(card))
+			continue;
+		if (card->scr.sda_vsn < SCR_SPEC_VER_1)
+			continue;
+
+		err = mmc_select_card(host, card);
+		if (err != MMC_ERR_NONE) {
+			mmc_card_set_dead(card);
+			continue;
+		}
+
+		memset(&cmd, 0, sizeof(struct mmc_command));
+
+		cmd.opcode = SD_SWITCH;
+		cmd.arg = 0x00FFFFF1;
+		cmd.flags = MMC_RSP_R1 | MMC_CMD_ADTC;
+
+		memset(&data, 0, sizeof(struct mmc_data));
+
+		mmc_set_data_timeout(&data, card, 0);
+
+		data.blksz = 64;
+		data.blocks = 1;
+		data.flags = MMC_DATA_READ;
+		data.sg = &sg;
+		data.sg_len = 1;
+
+		memset(&mrq, 0, sizeof(struct mmc_request));
+
+		mrq.cmd = &cmd;
+		mrq.data = &data;
+
+		sg_init_one(&sg, status, 64);
+
+		mmc_wait_for_req(host, &mrq);
+
+		if (cmd.error != MMC_ERR_NONE || data.error != MMC_ERR_NONE) {
+			mmc_card_set_dead(card);
+			continue;
+		}
+
+		if (status[13] & 0x02)
+			card->sw_caps.hs_max_dtr = 50000000;
+
+		memset(&cmd, 0, sizeof(struct mmc_command));
+
+		cmd.opcode = SD_SWITCH;
+		cmd.arg = 0x80FFFFF1;
+		cmd.flags = MMC_RSP_R1 | MMC_CMD_ADTC;
+
+		memset(&data, 0, sizeof(struct mmc_data));
+
+		mmc_set_data_timeout(&data, card, 0);
+
+		data.blksz = 64;
+		data.blocks = 1;
+		data.flags = MMC_DATA_READ;
+		data.sg = &sg;
+		data.sg_len = 1;
+
+		memset(&mrq, 0, sizeof(struct mmc_request));
+
+		mrq.cmd = &cmd;
+		mrq.data = &data;
+
+		sg_init_one(&sg, status, 64);
+
+		mmc_wait_for_req(host, &mrq);
+
+		if (cmd.error != MMC_ERR_NONE || data.error != MMC_ERR_NONE) {
+			mmc_card_set_dead(card);
+			continue;
+		}
+
+		if ((status[16] & 0xF) != 1) {
+			printk(KERN_WARNING "%s: Problem switching card "
+				"into high-speed mode!\n",
+				mmc_hostname(host));
+			continue;
+		}
+
+		mmc_card_set_highspeed(card);
+	}
+
+	kfree(status);
+
+	mmc_deselect_cards(host);
+}
+
 static unsigned int mmc_calculate_clock(struct mmc_host *host)
 {
 	struct mmc_card *card;
@@ -1164,9 +1274,12 @@ static unsigned int mmc_calculate_clock(struct mmc_host *host)
 
 	list_for_each_entry(card, &host->cards, node)
 		if (!mmc_card_dead(card)) {
-			if (mmc_card_highspeed(card)) {
+			if (mmc_card_highspeed(card) && mmc_card_sd(card)) {
+				if (max_dtr > card->sw_caps.hs_max_dtr)
+					max_dtr = card->sw_caps.hs_max_dtr;
+			} else if (mmc_card_highspeed(card) && !mmc_card_sd(card)) {
 				if (max_dtr > card->ext_csd.hs_max_dtr)
-			    		max_dtr = card->ext_csd.hs_max_dtr;
+					max_dtr = card->ext_csd.hs_max_dtr;
 			} else if (max_dtr > card->csd.max_dtr) {
 				max_dtr = card->csd.max_dtr;
 			}
@@ -1288,9 +1401,10 @@ static void mmc_setup(struct mmc_host *host)
 
 	mmc_read_csds(host);
 
-	if (host->mode == MMC_MODE_SD)
+	if (host->mode == MMC_MODE_SD) {
 		mmc_read_scrs(host);
-	else
+		mmc_read_switch_caps(host);
+	} else
 		mmc_process_ext_csds(host);
 }
 

include/linux/mmc/card.h

@@ -50,6 +50,10 @@ struct sd_scr {
 #define SD_SCR_BUS_WIDTH_4	(1<<2)
 };
 
+struct sd_switch_caps {
+	unsigned int		hs_max_dtr;
+};
+
 struct mmc_host;
 
 /*
@@ -66,7 +70,7 @@ struct mmc_card {
 #define MMC_STATE_BAD		(1<<2)		/* unrecognised device */
 #define MMC_STATE_SDCARD	(1<<3)		/* is an SD card */
 #define MMC_STATE_READONLY	(1<<4)		/* card is read-only */
-#define MMC_STATE_HIGHSPEED	(1<<5)		/* card is in mmc4 highspeed mode */
+#define MMC_STATE_HIGHSPEED	(1<<5)		/* card is in high speed mode */
 	u32			raw_cid[4];	/* raw card CID */
 	u32			raw_csd[4];	/* raw card CSD */
 	u32			raw_scr[2];	/* raw card SCR */
@@ -74,6 +78,7 @@ struct mmc_card {
 	struct mmc_csd		csd;		/* card specific */
 	struct mmc_ext_csd	ext_csd;	/* mmc v4 extended card specific */
 	struct sd_scr		scr;		/* extra SD information */
+	struct sd_switch_caps	sw_caps;	/* switch (CMD6) caps */
 };
 
 #define mmc_card_present(c)	((c)->state & MMC_STATE_PRESENT)

include/linux/mmc/protocol.h

@@ -82,6 +82,7 @@
   /* class 8 */
 /* This is basically the same command as for MMC with some quirks. */
 #define SD_SEND_RELATIVE_ADDR     3   /* bcr                     R6  */
+#define SD_SWITCH                 6   /* adtc [31:0] See below   R1  */
 
   /* Application commands */
 #define SD_APP_SET_BUS_WIDTH      6   /* ac   [1:0] bus width    R1  */
@@ -100,6 +101,19 @@
  *	[02:00] Command Set
  */
 
+/*
+ * SD_SWITCH argument format:
+ *
+ *      [31] Check (0) or switch (1)
+ *      [30:24] Reserved (0)
+ *      [23:20] Function group 6
+ *      [19:16] Function group 5
+ *      [15:12] Function group 4
+ *      [11:8] Function group 3
+ *      [7:4] Function group 2
+ *      [3:0] Function group 1
+ */
+
 /*
   MMC status in R1
   Type
@@ -284,6 +298,14 @@ struct _mmc_csd {
 #define MMC_SWITCH_MODE_CLEAR_BITS	0x02	/* Clear bits which are 1 in value */
 #define MMC_SWITCH_MODE_WRITE_BYTE	0x03	/* Set target to value */
 
+/*
+ * SCR field definitions
+ */
+
+#define SCR_SPEC_VER_0      0           /* Implements system specification 1.0 - 1.01 */
+#define SCR_SPEC_VER_1      1           /* Implements system specification 1.10 */
+#define SCR_SPEC_VER_2      2           /* Implements system specification 2.00 */
+
 /*
  * SD bus widths
  */