mmc: adjust switching to 4-bit mode for MMC devices

CMD6 is a normal command on MMC, but an application command on SD. And
the parameters and response type are different.

Change-Id: I0583b8a98cf18dc4d77d28066673d0d07229e161
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10934
Reviewed-by: Adrien Destugues <[email protected]>

headers/private/drivers/mmc.h

@@ -46,10 +46,10 @@ enum SD_COMMANDS {
 	// Basic commands, class 0
 	GO_IDLE_STATE = 0,
 	MMC_SEND_OP_COND = 1,
-		// MMC only,reserved in SD.
 	ALL_SEND_CID = 2,
 	SD_SEND_RELATIVE_ADDR = 3,
 	MMC_SET_RELATIVE_ADDR = 3,
+	MMC_SWITCH = 6, // Same command number as SD_SET_BUS_WIDTH, but this one is not an ACMD
 	SELECT_DESELECT_CARD = 7,
 	SD_SEND_IF_COND = 8,
 	MMC_SEND_EXT_CSD = 8,
@@ -76,6 +76,7 @@ enum SD_COMMANDS {
 };
 
 
+// Application commands are sent with a prefix CMD55 (SD_APP_CMD)
 enum SDHCI_APPLICATION_COMMANDS {
 	SD_SET_BUS_WIDTH = 6,
 	SD_SEND_OP_COND = 41,

src/add-ons/kernel/busses/mmc/sdhci.cpp

@@ -229,7 +229,6 @@ SdhciBus::ExecuteCommand(uint8_t command, uint32_t argument, uint32_t* response)
 		case SD_APP_CMD:
 		case SD_ERASE_WR_BLK_START:
 		case SD_ERASE_WR_BLK_END:
-		case SD_SET_BUS_WIDTH: // SD Application command
 			replyType = Command::kR1Type;
 			break;
 		case SELECT_DESELECT_CARD:
@@ -246,6 +245,12 @@ SdhciBus::ExecuteCommand(uint8_t command, uint32_t argument, uint32_t* response)
 			break;
 
 		// Commands defined with different reply types in SD and MMC specifications
+		case SD_SET_BUS_WIDTH: // SD application command. Also MMC_SWITCH, which is not.
+			if (fCardType == CARD_TYPE_MMC)
+				replyType = Command::kR1bType;
+			else
+				replyType = Command::kR1Type;
+			break;
 		case SD_SEND_RELATIVE_ADDR: // also MMC_SET_RELATIVE_ADDR
 			if (fCardType == CARD_TYPE_MMC)
 				replyType = Command::kR1Type;

src/add-ons/kernel/drivers/disk/mmc/mmc_disk.cpp

@@ -181,15 +181,46 @@ mmc_block_get_geometry(mmc_disk_driver_info* info, device_geometry* geometry)
 	// This function will be called before all data transfers, so we use this
 	// opportunity to switch the card to 4-bit data transfers (instead of the
 	// default 1 bit mode)
-	uint32_t cardStatus;
+	uint32_t cardStatus = 0;
+	status_t status = B_OK;
+
+	// TODO have the card type at hand instead of using the csd version here
+	if (csd.structure_version() < 3) {
 		const uint32 k4BitMode = 2;
 		info->mmc->execute_command(info->parent, info->parentCookie, info->rca,
 			SD_APP_CMD, info->rca << 16, &cardStatus);
-	info->mmc->execute_command(info->parent, info->parentCookie, info->rca,
+		status = info->mmc->execute_command(info->parent, info->parentCookie, info->rca,
 			SD_SET_BUS_WIDTH, k4BitMode, &cardStatus);
+	} else {
+		// TODO according to the eMMC spec, we should first run a test with CMD19 and CMD14 to
+		// determine if the 4-bit (and possibly the 8-bit) bus is wired, and also check if we need
+		// to switch to a different POWER_CLASS. See Jedec 84-B50 appendix A.6.3
+		//
+		// Command parameters for CMD6 (SWITCH):
+		// bits 31-26: set to 0
+		// bits 25-24: access (3 = write byte)
+		// bits 23-16: index (B7 = 183 in decimal is the offset of BUS_WIDTH in the EXT_CSD register)
+		// bits 15-8: value (1 = 4 bit mode)
+		// bits 7-3: set to 0
+		// bits 2-0: command set (kee using command set 0)
+		//
+		// See chapter 7.4.61 of the JEDEC spec as well as table 41 in section 6.10.4.
+		//
+		// The application note A.6.3 just gives the "magic" value to use without details as below:
+		const uint32 k4BitMode = 0x3B70100;
+		status = info->mmc->execute_command(info->parent, info->parentCookie, info->rca,
+			MMC_SWITCH, k4BitMode, &cardStatus);
+	}
 
+	TRACE("Card status after switching to 4 bit mode: %08x\n", cardStatus);
+
+	if (status == B_OK) {
 		// From now on we use 4 bit mode
+		TRACE("Switch to 4 bit mode for data transfers\n");
 		info->mmc->set_bus_width(info->parent, info->parentCookie, 4);
+	} else {
+		TRACE("Switching to 4 bit mode failed: %s\n", strerror(status));
+	}
 
 	return B_OK;
 }