sdhc: spi: power up with bus locked

Lock the SPI bus from access by other devices before applying power.
Keep the bus locked until the initial 74 clocks and CMD0 are sent to the
card. This prevents the card from incorrectly deciding that it should be
in SD mode due to bus traffic to other devices while it is going through
the init sequence.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

drivers/sdhc/sdhc_spi.c

@@ -104,6 +104,8 @@ struct sdhc_spi_data {
 	uint8_t scratch[MAX_CMD_READ];
 };
 
+static int sdhc_spi_send_cmd(const struct device *dev, struct sdhc_command *cmd, bool data_present);
+
 /* Receives a block of bytes */
 static int sdhc_spi_rx(const struct device *spi_dev, struct spi_config *spi_cfg,
 	uint8_t *buf, int len)
@@ -149,7 +151,7 @@ static int sdhc_spi_init_card(const struct device *dev)
 	const struct sdhc_spi_config *config = dev->config;
 	struct sdhc_spi_data *data = dev->data;
 	struct spi_config *spi_cfg = data->spi_cfg;
-	int ret, ret2;
+	int ret;
 
 	if (spi_cfg->frequency == 0) {
 		/* Use default 400KHZ frequency */
@@ -164,15 +166,31 @@ static int sdhc_spi_init_card(const struct device *dev)
 	/* the initial 74 clocks must be sent while CS is high */
 	spi_cfg->operation |= SPI_CS_ACTIVE_HIGH;
 	ret = sdhc_spi_rx(config->spi_dev, spi_cfg, data->scratch, 10);
+	spi_cfg->operation &= ~SPI_CS_ACTIVE_HIGH;
+
+	/* Send CMD0 immediately to force the transition to SPI mode before bus is unlocked.
+	 * Failing to do this can result in the SD card seeing transactions to other devices
+	 * on the same SPI bus and incorrectly deciding that it should be in SD mode.
+	 */
+	if (ret == 0) {
+		struct sdhc_command cmd0 = {
+			.opcode = SD_GO_IDLE_STATE,
+			.arg = 0,
+			.response_type = (SD_RSP_TYPE_NONE | SD_SPI_RSP_TYPE_R1),
+			.timeout_ms = 1000,
+			.retries = 1,
+		};
+
+		ret = sdhc_spi_send_cmd(dev, &cmd0, false);
+	}
 
 	/* Release lock on SPI bus */
-	ret2 = spi_release(config->spi_dev, spi_cfg);
-	spi_cfg->operation &= ~SPI_CS_ACTIVE_HIGH;
+	(void)spi_release(config->spi_dev, spi_cfg);
 
 	/* Release request for SPI bus to be active */
 	(void)pm_device_runtime_put(config->spi_dev);
 
-	return ret ? ret : ret2;
+	return ret;
 }
 
 /* Checks if SPI SD card is sending busy signal */
@@ -728,7 +746,11 @@ static int sdhc_spi_set_io(const struct device *dev, struct sdhc_io *ios)
 	if (data->power_mode != ios->power_mode) {
 		if (ios->power_mode == SDHC_POWER_ON) {
 			if (cfg->pwr_gpio.port) {
+				LOG_DBG("Locking SPI bus");
+				(void)spi_acquire(cfg->spi_dev, data->spi_cfg);
+
 				if (gpio_pin_set_dt(&cfg->pwr_gpio, 1)) {
+					(void)spi_release(cfg->spi_dev, data->spi_cfg);
 					return -EIO;
 				}
 
@@ -741,7 +763,7 @@ static int sdhc_spi_set_io(const struct device *dev, struct sdhc_io *ios)
 				LOG_INF("Powered up");
 			}
 
-			/* Send 74 clock cycles to start card */
+			/* Initialisation sequence for SPI mode */
 			if (sdhc_spi_init_card(dev) != 0) {
 				LOG_ERR("Card SCLK init sequence failed");
 				return -EIO;