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Subject[PATCH 2/2] dw: spi: add 'cs-override' DT property support
Date
Add support for an optional devicetree property called 'cs-override', which
is necessary for the Amazon Alpine spi controller. 'cs-override' is used in
the dw spi driver if specified in the devicetree. Otherwise, fall back to
driver default behavior, i.e., original dw IP hw driver behavior.

Signed-off-by: Talel Shenhar <talel@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
drivers/spi/spi-dw-mmio.c | 2 ++
drivers/spi/spi-dw.c | 6 ++++++
drivers/spi/spi-dw.h | 2 ++
3 files changed, 10 insertions(+)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index a768461..a2f7359 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -195,6 +195,8 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
goto out;
}
}
+ dws->cs_override = of_property_read_bool(pdev->dev.of_node,
+ "cs-override");
}

init_func = device_get_match_data(&pdev->dev);
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 3e205ab..eb4c3d1 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -144,6 +144,8 @@ void dw_spi_set_cs(struct spi_device *spi, bool enable)

if (!enable)
dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
+ else
+ dw_writel(dws, DW_SPI_SER, 0);
}
EXPORT_SYMBOL_GPL(dw_spi_set_cs);

@@ -463,6 +465,10 @@ static void spi_hw_init(struct device *dev, struct dw_spi *dws)
dws->fifo_len = (fifo == 1) ? 0 : fifo;
dev_dbg(dev, "Detected FIFO size: %u bytes\n", dws->fifo_len);
}
+
+ /* enable HW fixup for explicit CS deselect for Amazon's alpine chip */
+ if (dws->cs_override)
+ dw_writel(dws, DW_SPI_CS_OVERRIDE, 0xF);
}

int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 0168b08..c9c1588 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -32,6 +32,7 @@
#define DW_SPI_IDR 0x58
#define DW_SPI_VERSION 0x5c
#define DW_SPI_DR 0x60
+#define DW_SPI_CS_OVERRIDE 0xf4

/* Bit fields in CTRLR0 */
#define SPI_DFS_OFFSET 0
@@ -109,6 +110,7 @@ struct dw_spi {
u32 fifo_len; /* depth of the FIFO buffer */
u32 max_freq; /* max bus freq supported */

+ int cs_override;
u32 reg_io_width; /* DR I/O width in bytes */
u16 bus_num;
u16 num_cs; /* supported slave numbers */
--
2.7.4
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