spi: s3c64xx: add s3c64xx_iowrite{8,16}_32_rep accessors

Allow SoCs that require 32 bits register accesses to write data in
chunks of 8 or 16 bits. One SoC that requires 32 bit register accesses
is the google gs101. The operation is rare, thus open code it in the
driver rather than making it generic (through asm-generic/io.h).

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240207111516.2563218-4-tudor.ambarus@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-s3c64xx.c

@@ -142,6 +142,7 @@ struct s3c64xx_spi_dma_data {
  *	prescaler unit.
  * @clk_ioclk: True if clock is present on this device
  * @has_loopback: True if loopback mode can be supported
+ * @use_32bit_io: True if the SoC allows only 32-bit register accesses.
  *
  * The Samsung s3c64xx SPI controller are used on various Samsung SoC's but
  * differ in some aspects such as the size of the fifo and spi bus clock
@@ -158,6 +159,7 @@ struct s3c64xx_spi_port_config {
 	bool	clk_from_cmu;
 	bool	clk_ioclk;
 	bool	has_loopback;
+	bool	use_32bit_io;
 };
 
 /**
@@ -414,6 +416,30 @@ static bool s3c64xx_spi_can_dma(struct spi_controller *host,
 
 }
 
+static void s3c64xx_iowrite8_32_rep(volatile void __iomem *addr,
+				    const void *buffer, unsigned int count)
+{
+	if (count) {
+		const u8 *buf = buffer;
+
+		do {
+			__raw_writel(*buf++, addr);
+		} while (--count);
+	}
+}
+
+static void s3c64xx_iowrite16_32_rep(volatile void __iomem *addr,
+				     const void *buffer, unsigned int count)
+{
+	if (count) {
+		const u16 *buf = buffer;
+
+		do {
+			__raw_writel(*buf++, addr);
+		} while (--count);
+	}
+}
+
 static void s3c64xx_iowrite_rep(const struct s3c64xx_spi_driver_data *sdd,
 				struct spi_transfer *xfer)
 {
@@ -426,10 +452,16 @@ static void s3c64xx_iowrite_rep(const struct s3c64xx_spi_driver_data *sdd,
 		iowrite32_rep(addr, buf, len / 4);
 		break;
 	case 16:
-		iowrite16_rep(addr, buf, len / 2);
+		if (sdd->port_conf->use_32bit_io)
+			s3c64xx_iowrite16_32_rep(addr, buf, len / 2);
+		else
+			iowrite16_rep(addr, buf, len / 2);
 		break;
 	default:
-		iowrite8_rep(addr, buf, len);
+		if (sdd->port_conf->use_32bit_io)
+			s3c64xx_iowrite8_32_rep(addr, buf, len);
+		else
+			iowrite8_rep(addr, buf, len);
 		break;
 	}
 }