spi: rspi: Fix register initialization while runtime-suspended

The Renesas RSPI/QSPI driver performs SPI controller register
initialization in its spi_operations.setup() callback, without calling
pm_runtime_get_sync() first, which may cause spurious failures.

So far this went unnoticed, as this SPI controller is typically used
with a single SPI NOR FLASH containing the boot loader:
  1. If the device's module clock is still enabled (left enabled by the
     bootloader, and not yet disabled by the clk_disable_unused() late
     initcall), register initialization succeeds,
  2. If the device's module clock is disabled, register writes don't
     seem to cause lock-ups or crashes.
     Data received in the first SPI message may be corrupted, though.
     Subsequent SPI messages seem to be OK.
     E.g. on r8a7791/koelsch, one bit is lost while receiving the 6th
     byte of the JEDEC ID for the s25fl512s FLASH, corrupting that byte
     and all later bytes.  But until commit a2126b0a ("mtd:
     spi-nor: refine Spansion S25FL512S ID"), the 6th byte was not
     considered for FLASH identification.

Fix this by moving all initialization from the .setup() to the
.prepare_message() callback.  The latter is always called after the
device has been runtime-resumed by the SPI core.

This also makes the driver follow the rule that .setup() must not change
global driver state or register values, as that might break a transfer
in progress.

Fixes: 490c9774 ("spi: rspi: Add runtime PM support, using spi core auto_runtime_pm")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rspi.c

@@ -868,28 +868,6 @@ static int qspi_transfer_one(struct spi_controller *ctlr,
 	}
 }
 
-static int rspi_setup(struct spi_device *spi)
-{
-	struct rspi_data *rspi = spi_controller_get_devdata(spi->controller);
-
-	rspi->max_speed_hz = spi->max_speed_hz;
-
-	rspi->spcmd = SPCMD_SSLKP;
-	if (spi->mode & SPI_CPOL)
-		rspi->spcmd |= SPCMD_CPOL;
-	if (spi->mode & SPI_CPHA)
-		rspi->spcmd |= SPCMD_CPHA;
-
-	/* CMOS output mode and MOSI signal from previous transfer */
-	rspi->sppcr = 0;
-	if (spi->mode & SPI_LOOP)
-		rspi->sppcr |= SPPCR_SPLP;
-
-	set_config_register(rspi, 8);
-
-	return 0;
-}
-
 static u16 qspi_transfer_mode(const struct spi_transfer *xfer)
 {
 	if (xfer->tx_buf)
@@ -959,8 +937,24 @@ static int rspi_prepare_message(struct spi_controller *ctlr,
 				struct spi_message *msg)
 {
 	struct rspi_data *rspi = spi_controller_get_devdata(ctlr);
+	struct spi_device *spi = msg->spi;
 	int ret;
 
+	rspi->max_speed_hz = spi->max_speed_hz;
+
+	rspi->spcmd = SPCMD_SSLKP;
+	if (spi->mode & SPI_CPOL)
+		rspi->spcmd |= SPCMD_CPOL;
+	if (spi->mode & SPI_CPHA)
+		rspi->spcmd |= SPCMD_CPHA;
+
+	/* CMOS output mode and MOSI signal from previous transfer */
+	rspi->sppcr = 0;
+	if (spi->mode & SPI_LOOP)
+		rspi->sppcr |= SPPCR_SPLP;
+
+	set_config_register(rspi, 8);
+
 	if (msg->spi->mode &
 	    (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)) {
 		/* Setup sequencer for messages with multiple transfer modes */
@@ -1267,7 +1261,6 @@ static int rspi_probe(struct platform_device *pdev)
 	init_waitqueue_head(&rspi->wait);
 
 	ctlr->bus_num = pdev->id;
-	ctlr->setup = rspi_setup;
 	ctlr->auto_runtime_pm = true;
 	ctlr->transfer_one = ops->transfer_one;
 	ctlr->prepare_message = rspi_prepare_message;