[PATCH 2/2] dw: spi: add support for Amazon's Alpine spi controller

[Talel Shenhar]

Add support for a new devicetree compatible string called
'amazon,alpine-apb-ssi', which is necessary for the Amazon Alpine spi
controller. 'amazon,alpine-dw-apb-ssi' 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 <ta...@amazon.com>
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
 drivers/spi/spi-dw-mmio.c | 9 +++++++++
 drivers/spi/spi-dw.c      | 6 ++++++
 drivers/spi/spi-dw.h      | 2 ++
 3 files changed, 17 insertions(+)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index a768461..3ffb6a40 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -126,6 +126,14 @@ static int dw_spi_mscc_jaguar2_init(struct platform_device 
*pdev,
                                JAGUAR2_IF_SI_OWNER_OFFSET);
 }
 
+static int dw_spi_alpine_init(struct platform_device *pdev,
+                             struct dw_spi_mmio *dwsmmio)
+{
+       dwsmmio->dws.cs_override = 1;
+
+       return 0;
+}
+
 static int dw_spi_mmio_probe(struct platform_device *pdev)
 {
        int (*init_func)(struct platform_device *pdev,
@@ -230,6 +238,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
        { .compatible = "snps,dw-apb-ssi", },
        { .compatible = "mscc,ocelot-spi", .data = dw_spi_mscc_ocelot_init},
        { .compatible = "mscc,jaguar2-spi", .data = dw_spi_mscc_jaguar2_init},
+       { .compatible = "amazon,alpine-dw-apb-ssi", .data = dw_spi_alpine_init},
        { /* end of table */}
 };
 MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 3e205ab..b705f2b 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 if (dws->cs_override)
+               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