mmc: core: fix multi-bit bus width without high-speed mode

Commit 577fb13 ("mmc: rework selection of bus speed mode")
refactored bus width selection code to mmc_select_bus_width().

However, it also altered the behavior to not call the selection code in
non-high-speed modes anymore.

This causes 1-bit mode to always be used when the high-speed mode is not
enabled, even though 4-bit and 8-bit bus are valid bus widths in the
backwards-compatibility (legacy) mode as well (see e.g. 5.3.2 Bus Speed
Modes in JEDEC 84-B50). This results in a significant regression in
transfer speeds.

Fix the code to allow 4-bit and 8-bit widths even without high-speed
mode, as before.

Tested with a Zynq-7000 PicoZed 7020 board.

Fixes: 577fb13 ("mmc: rework selection of bus speed mode")
Signed-off-by: Anssi Hannula <[email protected]>
Cc: <[email protected]>
Signed-off-by: Ulf Hansson <[email protected]>

drivers/mmc/core/mmc.c

@@ -1706,10 +1706,10 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		err = mmc_select_hs400(card);
 		if (err)
 			goto free_card;
-	} else if (mmc_card_hs(card)) {
+	} else {
 		/* Select the desired bus width optionally */
 		err = mmc_select_bus_width(card);
-		if (err > 0) {
+		if (err > 0 && mmc_card_hs(card)) {
 			err = mmc_select_hs_ddr(card);
 			if (err)
 				goto free_card;