[PATCH 02/32] spi: dw: Add support for 32-bits ctrlr0 layout

[Damien Le Moal <damien.lemoal@xxxxxxx>]

Synopsis DesignWare DW_apb_ssi version 4 defines a 32-bit layout of
the ctrlr0 register for SPI masters. The layout of ctrlr0 is:

|   31 .. 23  | 22 .. 21 | 20 .. 16 |
| other stuff | spi_frf  |  dfs_32  |

|   15 .. 10  | 9 .. 8 | 7 .. 6 | 5 .. 4 | 3 .. 0 |
| other stuff |  tmod  |  mode  |  frf   |  dfs   |

Th main difference of this layout with the 16-bits version is the data
frame format field which resides in bits 16..20 instead of bits 3..0.

Introduce the DW SPI capability flag DW_SPI_CAP_DFS_32 to let a
platform signal that this layout is in use. Modify
dw_spi_update_config() to test this capability flag to set the data
frame format field at the correct register location.

Suggested-by: Sean Anderson <seanga2@xxxxxxxxx>
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
 drivers/spi/spi-dw-core.c | 8 ++++++--
 drivers/spi/spi-dw.h      | 9 +++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 2e50cc0a9291..841c85247f01 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -311,8 +311,12 @@ void dw_spi_update_config(struct dw_spi *dws, struct spi_device *spi,
 	u32 speed_hz;
 	u16 clk_div;
 
-	/* CTRLR0[ 4/3: 0] Data Frame Size */
-	cr0 |= (cfg->dfs - 1);
+	if (!(dws->caps & DW_SPI_CAP_DFS_32))
+		/* CTRLR0[ 4/3: 0] Data Frame Size */
+		cr0 |= (cfg->dfs - 1);
+	else
+		/* CTRLR0[20: 16] Data Frame Size */
+		cr0 |= (cfg->dfs - 1) << DWC_APB_CTRLR0_32_DFS_OFFSET;
 
 	if (!(dws->caps & DW_SPI_CAP_DWC_SSI))
 		/* CTRLR0[ 9:8] Transfer Mode */
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index faf40cb66498..48a11a51a407 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -9,6 +9,7 @@
 #include <linux/io.h>
 #include <linux/scatterlist.h>
 #include <linux/spi/spi-mem.h>
+#include <linux/bitfield.h>
 
 /* Register offsets */
 #define DW_SPI_CTRLR0			0x00
@@ -72,6 +73,13 @@
 #define DWC_SSI_CTRLR0_FRF_OFFSET	6
 #define DWC_SSI_CTRLR0_DFS_OFFSET	0
 
+/*
+ * Bit fields in CTRLR0 for DWC_apb_ssi v4 32-bits ctrlr0.
+ * Based on DW_apb_ssi Databook v4.02a.
+ */
+#define DWC_APB_CTRLR0_32_DFS_OFFSET	16
+#define DWC_APB_CTRLR0_32_DFS_MASK	GENMASK(20, 16)
+
 /*
  * For Keem Bay, CTRLR0[31] is used to select controller mode.
  * 0: SSI is slave
@@ -121,6 +129,7 @@ enum dw_ssi_type {
 #define DW_SPI_CAP_CS_OVERRIDE		BIT(0)
 #define DW_SPI_CAP_KEEMBAY_MST		BIT(1)
 #define DW_SPI_CAP_DWC_SSI		BIT(2)
+#define DW_SPI_CAP_DFS_32		BIT(3)
 
 /* Slave spi_transfer/spi_mem_op related */
 struct dw_spi_cfg {
-- 
2.28.0