spi: dw: Convert CS-override to DW SPI capabilities

There are several vendor-specific versions of the DW SPI controllers,
each of which may have some peculiarities with respect to the original
IP-core. Seeing it has already caused adding flags and a callback into the
DW SPI private data, let's introduce a generic capabilities interface to
tune the generic DW SPI controller driver up in accordance with the
particular controller specifics. It's done by converting a simple
Alpine-specific CS-override capability into the DW SPI controller
capability activated by setting the DW_SPI_CAP_CS_OVERRIDE flag.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-10-Sergey.Semin@baikalelectronics.ruSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-core.c

@@ -104,7 +104,7 @@ void dw_spi_set_cs(struct spi_device *spi, bool enable)
 	 */
 	if (cs_high == enable)
 		dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
-	else if (dws->cs_override)
+	else if (dws->caps & DW_SPI_CAP_CS_OVERRIDE)
 		dw_writel(dws, DW_SPI_SER, 0);
 }
 EXPORT_SYMBOL_GPL(dw_spi_set_cs);
@@ -444,7 +444,7 @@ static void spi_hw_init(struct device *dev, struct dw_spi *dws)
 	}
 
 	/* enable HW fixup for explicit CS deselect for Amazon's alpine chip */
-	if (dws->cs_override)
+	if (dws->caps & DW_SPI_CAP_CS_OVERRIDE)
 		dw_writel(dws, DW_SPI_CS_OVERRIDE, 0xF);
 }
 

drivers/spi/spi-dw-mmio.c

@@ -204,7 +204,7 @@ static int dw_spi_mscc_sparx5_init(struct platform_device *pdev,
 static int dw_spi_alpine_init(struct platform_device *pdev,
 			      struct dw_spi_mmio *dwsmmio)
 {
-	dwsmmio->dws.cs_override = 1;
+	dwsmmio->dws.caps = DW_SPI_CAP_CS_OVERRIDE;
 
 	/* Register hook to configure CTRLR0 */
 	dwsmmio->dws.update_cr0 = dw_spi_update_cr0;

drivers/spi/spi-dw.h

@@ -2,6 +2,7 @@
 #ifndef DW_SPI_HEADER_H
 #define DW_SPI_HEADER_H
 
+#include <linux/bits.h>
 #include <linux/completion.h>
 #include <linux/debugfs.h>
 #include <linux/irqreturn.h>
@@ -98,6 +99,9 @@ enum dw_ssi_type {
 	SSI_NS_MICROWIRE,
 };
 
+/* DW SPI capabilities */
+#define DW_SPI_CAP_CS_OVERRIDE		BIT(0)
+
 struct dw_spi;
 struct dw_spi_dma_ops {
 	int (*dma_init)(struct device *dev, struct dw_spi *dws);
@@ -118,7 +122,8 @@ struct dw_spi {
 	u32			fifo_len;	/* depth of the FIFO buffer */
 	u32			max_freq;	/* max bus freq supported */
 
-	int			cs_override;
+	u32			caps;		/* DW SPI capabilities */
+
 	u32			reg_io_width;	/* DR I/O width in bytes */
 	u16			bus_num;
 	u16			num_cs;		/* supported slave numbers */