linux-kernel - [PATCH v2 3/4] spi: s3c64xx: add s3c64xx_iowrite{8,16}_32

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Date: Wed,  7 Feb 2024 11:15:15 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: broonie@...nel.org,
	andi.shyti@...nel.org,
	semen.protsenko@...aro.org
Cc: krzysztof.kozlowski@...aro.org,
	alim.akhtar@...sung.com,
	linux-spi@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	andre.draszik@...aro.org,
	peter.griffin@...aro.org,
	kernel-team@...roid.com,
	willmcvicker@...gle.com,
	robh+dt@...nel.org,
	conor+dt@...nel.org,
	devicetree@...r.kernel.org,
	Tudor Ambarus <tudor.ambarus@...aro.org>
Subject: [PATCH v2 3/4] 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@...aro.org>
---
 drivers/spi/spi-s3c64xx.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index eb79c6e4f509..014fcc933c90 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/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;
 	}
 }
-- 
2.43.0.687.g38aa6559b0-goog