spi: cadence-qspi: Make sure write protection is disabled

Renesas RZ/N1 QSPI controllers embed the Cadence IP with some
modifications. For instance, they feature a write protection of the
direct mapping at the controller level, with this feature all data
writes to the AHB region are aborted.

Despite the fact that the flag setting write protection is disabled by
default, Bootloaders may (and actually do) set it, so mark this feature
as being available with a specific flag to, if applicable, make sure it
is disabled.

Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Miquel Raynal (Schneider Electric) <miquel.raynal@bootlin.com>
Tested-by: Santhosh Kumar K <s-k6@ti.com>
Link: https://patch.msgid.link/20260122-schneider-6-19-rc1-qspi-v4-12-f9c21419a3e6@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: miquelraynal

drivers/spi/spi-cadence-quadspi.c

@@ -48,6 +48,7 @@ static_assert(CQSPI_MAX_CHIPSELECT <= SPI_DEVICE_CS_CNT_MAX);
 #define CQSPI_DISABLE_STIG_MODE		BIT(9)
 #define CQSPI_DISABLE_RUNTIME_PM	BIT(10)
 #define CQSPI_NO_INDIRECT_MODE		BIT(11)
+#define CQSPI_HAS_WR_PROTECT		BIT(12)
 
 /* Capabilities */
 #define CQSPI_SUPPORTS_OCTAL		BIT(0)
@@ -220,6 +221,8 @@ struct cqspi_driver_platdata {
 #define CQSPI_REG_IRQSTATUS			0x40
 #define CQSPI_REG_IRQMASK			0x44
 
+#define CQSPI_REG_WR_PROT_CTRL			0x58
+
 #define CQSPI_REG_INDIRECTRD			0x60
 #define CQSPI_REG_INDIRECTRD_START_MASK		BIT(0)
 #define CQSPI_REG_INDIRECTRD_CANCEL_MASK	BIT(1)
@@ -1643,6 +1646,10 @@ static void cqspi_controller_init(struct cqspi_st *cqspi)
 		       cqspi->iobase + CQSPI_REG_INDIRECTWRWATERMARK);
 	}
 
+	/* Disable write protection at controller level */
+	if (cqspi->ddata && cqspi->ddata->quirks & CQSPI_HAS_WR_PROTECT)
+		writel(0, cqspi->iobase + CQSPI_REG_WR_PROT_CTRL);
+
 	/* Disable direct access controller */
 	if (!cqspi->use_direct_mode) {
 		reg = readl(cqspi->iobase + CQSPI_REG_CONFIG);