dw: spi: add support for Amazon's Alpine spi controller

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 <talel@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>

3 files changed, 17 insertions, 0 deletions

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index a768461614a0..3ffb6a40fe0c 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 3e205ab60cd4..b705f2bdb8b9 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 0168b08364d5..c9c15881e982 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 */