mmc: support for SPI bus type

- Introduce the bus_type accessor, which allows to skip card selection
  and timing settings in SPI mode;
- Add MMC_CMD_IS_APP flag for commands followed by the APP command,
  which is required by the upcoming MMCSPI driver.

Reviewed by:	pkelsey
Sponsored by:	UKRI
Differential Revision:	https://reviews.freebsd.org/D49249

sys/dev/mmc/bridge.h

@@ -103,6 +103,10 @@ enum mmc_chip_select {
 	cs_dontcare = 0, cs_high, cs_low
 };
 
+enum mmc_bus_type {
+	bus_type_default = 0, bus_type_spi
+};
+
 enum mmc_bus_width {
 	bus_width_1 = 0, bus_width_4 = 2, bus_width_8 = 3
 };
@@ -123,6 +127,7 @@ struct mmc_ios {
 	uint32_t	clock;	/* Speed of the clock in Hz to move data */
 	enum mmc_vdd	vdd;	/* Voltage to apply to the power pins */
 	enum mmc_vccq	vccq;	/* Voltage to use for signaling */
+	enum mmc_bus_type bus_type;
 	enum mmc_bus_mode bus_mode;
 	enum mmc_chip_select chip_select;
 	enum mmc_bus_width bus_width;

sys/dev/mmc/mmc.c

@@ -701,6 +701,10 @@ mmc_select_card(struct mmc_softc *sc, uint16_t rca)
 {
 	int err, flags;
 
+	/* No card selection in SPI mode. */
+	if (mmcbr_get_bus_type(sc->dev) == bus_type_spi)
+		return (MMC_ERR_NONE);
+
 	flags = (rca ? MMC_RSP_R1B : MMC_RSP_NONE) | MMC_CMD_AC;
 	sc->retune_paused++;
 	err = mmc_wait_for_command(sc, MMC_SELECT_CARD, (uint32_t)rca << 16,
@@ -900,6 +904,10 @@ mmc_set_timing(struct mmc_softc *sc, struct mmc_ivars *ivar,
 	uint8_t	value;
 	int err;
 
+	/* No timings in SPI mode. */
+	if (mmcbr_get_bus_type(sc->dev) == bus_type_spi)
+		return (MMC_ERR_NONE);
+
 	if (mmcbr_get_mode(sc->dev) == mode_sd) {
 		switch (timing) {
 		case bus_timing_normal:

sys/dev/mmc/mmc_subr.c

@@ -112,6 +112,8 @@ mmc_wait_for_app_cmd(device_t busdev, device_t dev, uint16_t rca,
 
 	sc = device_get_softc(busdev);
 
+	cmd->flags |= MMC_CMD_IS_APP;
+
 	/* Squelch error reporting at lower levels, we report below. */
 	sc->squelched++;
 	do {

sys/dev/mmc/mmcbrvar.h

@@ -60,6 +60,7 @@
 #include "mmcbr_if.h"
 
 enum mmcbr_device_ivars {
+    MMCBR_IVAR_BUS_TYPE,
     MMCBR_IVAR_BUS_MODE,
     MMCBR_IVAR_BUS_WIDTH,
     MMCBR_IVAR_CHIP_SELECT,
@@ -113,6 +114,17 @@ mmcbr_get_retune_req(device_t dev)
 	return ((int)v);
 }
 
+static int __inline
+mmcbr_get_bus_type(device_t dev)
+{
+	uintptr_t v;
+
+	if (__predict_false(BUS_READ_IVAR(device_get_parent(dev), dev,
+	    MMCBR_IVAR_BUS_TYPE, &v) != 0))
+		return (bus_type_default);
+	return ((int)v);
+}
+
 /*
  * Convenience wrappers for the mmcbr interface
  */

sys/dev/mmc/mmcreg.h

@@ -80,6 +80,7 @@ struct mmc_command {
 #define	MMC_CMD_BC	(2ul << 5)	/* Broadcast command, no response */
 #define	MMC_CMD_BCR	(3ul << 5)	/* Broadcast command with response */
 #define	MMC_CMD_MASK	(3ul << 5)
+#define	MMC_CMD_IS_APP  (1ul << 7)	/* Next cmd after MMC_APP_CMD */
 
 /* Possible response types defined in the standard: */
 #define	MMC_RSP_NONE	(0)