[U-Boot] [PATCH v2] spi: kirkwood_spi: implement workaround for FE-9144572

[Chris Packham]

Erratum NO. FE-9144572: The device SPI interface supports frequencies of
up to 50 MHz.  However, due to this erratum, when the device core clock
is 250 MHz and the SPI interfaces is configured for 50MHz SPI clock and
CPOL=CPHA=1 there might occur data corruption on reads from the SPI
device.

Implement the workaround by setting the TMISO_SAMPLE value to 0x2
in the timing1 register.

Signed-off-by: Chris Packham <judge.packham at gmail.com>
Reviewed-by: Stefan Roese <sr at denx.de>
---
I've based this as much as I can on the equivalent implementation in the
Linux kernel[1], but there are differences in the u-boot spi
infrastructure that means I can't be as specific when qualifying whether
the workaround is needed.

[1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/spi/spi-orion.c#n248

Changes in v2:
- collect reviewed-by from Stefan
- remove mvebu_spi_type
- describe errata above mvebu_spi_50mhz_ac_timing_erratum

 arch/arm/include/asm/arch-mvebu/spi.h |  6 ++++
 drivers/spi/kirkwood_spi.c            | 61 +++++++++++++++++++++++++++++++++--
 2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/arch-mvebu/spi.h b/arch/arm/include/asm/arch-mvebu/spi.h
index 3545aed17347..1de510ea6da9 100644
--- a/arch/arm/include/asm/arch-mvebu/spi.h
+++ b/arch/arm/include/asm/arch-mvebu/spi.h
@@ -57,6 +57,12 @@ struct kwspi_registers {
 #define KWSPI_TXLSBF		(1 << 13)
 #define KWSPI_RXLSBF		(1 << 14)
 
+/* Timing Parameters 1 Register */
+#define KW_SPI_TMISO_SAMPLE_OFFSET	6
+#define KW_SPI_TMISO_SAMPLE_MASK	(0x3 << KW_SPI_TMISO_SAMPLE_OFFSET)
+#define KW_SPI_TMISO_SAMPLE_1		(1 << KW_SPI_TMISO_SAMPLE_OFFSET)
+#define KW_SPI_TMISO_SAMPLE_2		(2 << KW_SPI_TMISO_SAMPLE_OFFSET)
+
 #define KWSPI_IRQUNMASK		1 /* unmask SPI interrupt */
 #define KWSPI_IRQMASK		0 /* mask SPI interrupt */
 #define KWSPI_SMEMRDIRQ		1 /* SerMem data xfer ready irq */
diff --git a/drivers/spi/kirkwood_spi.c b/drivers/spi/kirkwood_spi.c
index 0c6bd295cde9..5b1ac0eed634 100644
--- a/drivers/spi/kirkwood_spi.c
+++ b/drivers/spi/kirkwood_spi.c
@@ -243,6 +243,10 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 
 /* Here now the DM part */
 
+struct mvebu_spi_dev {
+	bool			is_errata_50mhz_ac;
+};
+
 struct mvebu_spi_platdata {
 	struct kwspi_registers *spireg;
 };
@@ -269,10 +273,38 @@ static int mvebu_spi_set_speed(struct udevice *bus, uint hz)
 	return 0;
 }
 
+/*
+ * FE-9144572: The device SPI interface supports frequencies of up to 50 MHz.
+ * However, due to this erratum, when the device core clock is 250 MHz and the
+ * SPI interfaces is configured for 50MHz SPI clock and CPOL=CPHA=1 there might
+ * occur data corruption on reads from the SPI device.
+ *
+ * Workaround: Set the TMISO_SAMPLE value to 0x2 in the SPI Timing Parameters 1
+ * register
+ */
+static void mvebu_spi_50mhz_ac_timing_erratum(struct udevice *bus, uint mode)
+{
+	struct mvebu_spi_platdata *plat = dev_get_platdata(bus);
+	struct kwspi_registers *reg = plat->spireg;
+	u32 data = readl(&reg->timing1);
+
+	data &= ~KW_SPI_TMISO_SAMPLE_MASK;
+
+	if (CONFIG_SYS_TCLK == 250000000 &&
+	    mode & SPI_CPOL &&
+	    mode & SPI_CPHA)
+		data |= KW_SPI_TMISO_SAMPLE_2;
+	else
+		data |= KW_SPI_TMISO_SAMPLE_1;
+
+	writel(data, &reg->timing1);
+}
+
 static int mvebu_spi_set_mode(struct udevice *bus, uint mode)
 {
 	struct mvebu_spi_platdata *plat = dev_get_platdata(bus);
 	struct kwspi_registers *reg = plat->spireg;
+	const struct mvebu_spi_dev *drvdata;
 	u32 data = readl(&reg->cfg);
 
 	data &= ~(KWSPI_CPHA | KWSPI_CPOL | KWSPI_RXLSBF | KWSPI_TXLSBF);
@@ -286,6 +318,10 @@ static int mvebu_spi_set_mode(struct udevice *bus, uint mode)
 
 	writel(data, &reg->cfg);
 
+	drvdata = (struct mvebu_spi_dev *)dev_get_driver_data(bus);
+	if (drvdata->is_errata_50mhz_ac)
+		mvebu_spi_50mhz_ac_timing_erratum(bus, mode);
+
 	return 0;
 }
 
@@ -343,10 +379,29 @@ static const struct dm_spi_ops mvebu_spi_ops = {
 	 */
 };
 
+static const struct mvebu_spi_dev armada_xp_spi_dev_data = {
+};
+
+static const struct mvebu_spi_dev armada_375_spi_dev_data = {
+};
+
+static const struct mvebu_spi_dev armada_380_spi_dev_data = {
+	.is_errata_50mhz_ac = true,
+};
+
 static const struct udevice_id mvebu_spi_ids[] = {
-	{ .compatible = "marvell,armada-375-spi" },
-	{ .compatible = "marvell,armada-380-spi" },
-	{ .compatible = "marvell,armada-xp-spi" },
+	{
+		.compatible = "marvell,armada-375-spi",
+		.data = (ulong)&armada_375_spi_dev_data
+	},
+	{
+		.compatible = "marvell,armada-380-spi",
+		.data = (ulong)&armada_380_spi_dev_data
+	},
+	{
+		.compatible = "marvell,armada-xp-spi",
+		.data = (ulong)&armada_xp_spi_dev_data
+	},
 	{ }
 };
 
-- 
2.14.2