[U-Boot] [PATCH] mmc: Do not issue CMD 6 on SD 1.00 and SD 1.01

[Marek Vasut]

According to SD Specifications Part 1 Physical Layer Simplified Specification
Version 6.00 August 29, 2018, section 4.3.10 (Switch Function Command) and
section 5.6 (SCR register), SD cards version 1.00 and 1.01 do not support the
SD CMD 6.

Currently, U-Boot will issue CMD 6 unconditionally in sd_set_card_speed()
while configuring the bus for selected frequency. This will make SD cards
version 1.00 and 1.01 time out and thus fail detection altogether.

Fix this by not sending CMD 6 on such cards. Tested on Matsushita Electric
Industrial Co., Ltd. Japan RP-SD008B / Victor 8MB SD card, CU-SD008, which
is correctly detected with this patch as:

Device: sd at ee160000
Manufacturer ID: 1
OEM: 5041
Name: S008B
Bus Speed: 25000000
Mode : SD Legacy
Rd Block Len: 512
SD version 1.0
High Capacity: No
Capacity: 6.5 MiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes

Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
---
 drivers/mmc/mmc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 585951cd78..8c06e7a16e 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1289,6 +1289,10 @@ static int sd_set_card_speed(struct mmc *mmc, enum bus_mode mode)
 	ALLOC_CACHE_ALIGN_BUFFER(uint, switch_status, 16);
 	int speed;
 
+	/* SD version 1.00 and 1.01 does not support CMD 6 */
+	if (mmc->version == SD_VERSION_1_0)
+		return 0;
+
 	switch (mode) {
 	case SD_LEGACY:
 		speed = UHS_SDR12_BUS_SPEED;
-- 
2.18.0