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Subject[PATCH v3 02/12] spi: spi-fsl-dspi: Fix little endian access to PUSHR CMD and TXDATA
Date
From: Vladimir Oltean <vladimir.oltean@nxp.com>

In XSPI mode, the 32-bit PUSHR register can be written to separately:
the higher 16 bits are for commands and the lower 16 bits are for data.

This has nicely been hacked around, by defining a second regmap with a
width of 16 bits, and effectively splitting a 32-bit register into 2
16-bit ones, from the perspective of this regmap_pushr.

The problem is the assumption about the controller's endianness. If the
controller is little endian (such as anything post-LS1046A), then the
first 2 bytes, in the order imposed by memory layout, will actually hold
the TXDATA, and the last 2 bytes will hold the CMD.

So take the controller's endianness into account when performing split
writes to PUSHR. The obvious and simple solution would have been to call
regmap_get_val_endian(), but that is an internal regmap function and we
don't want to change regmap just for this. Therefore, we just re-read
the "big-endian" device tree property.

Fixes: 58ba07ec79e6 ("spi: spi-fsl-dspi: Add support for XSPI mode registers")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v4:
None.

Changes in v3:
None.

Changes in v2:
Parse "big-endian" device tree bindings instead of taking the decision
based on compatible SoC.

drivers/spi/spi-fsl-dspi.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 6ca35881881b..be717776dd98 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -103,10 +103,6 @@
#define SPI_FRAME_BITS(bits) SPI_CTAR_FMSZ((bits) - 1)
#define SPI_FRAME_EBITS(bits) SPI_CTARE_FMSZE(((bits) - 1) >> 4)

-/* Register offsets for regmap_pushr */
-#define PUSHR_CMD 0x0
-#define PUSHR_TX 0x2
-
#define DMA_COMPLETION_TIMEOUT msecs_to_jiffies(3000)

struct chip_data {
@@ -240,6 +236,13 @@ struct fsl_dspi {

int words_in_flight;

+ /*
+ * Offsets for CMD and TXDATA within SPI_PUSHR when accessed
+ * individually (in XSPI mode)
+ */
+ int pushr_cmd;
+ int pushr_tx;
+
void (*host_to_dev)(struct fsl_dspi *dspi, u32 *txdata);
void (*dev_to_host)(struct fsl_dspi *dspi, u32 rxdata);
};
@@ -673,12 +676,12 @@ static void dspi_pushr_cmd_write(struct fsl_dspi *dspi, u16 cmd)
*/
if (dspi->len > dspi->oper_word_size)
cmd |= SPI_PUSHR_CMD_CONT;
- regmap_write(dspi->regmap_pushr, PUSHR_CMD, cmd);
+ regmap_write(dspi->regmap_pushr, dspi->pushr_cmd, cmd);
}

static void dspi_pushr_txdata_write(struct fsl_dspi *dspi, u16 txdata)
{
- regmap_write(dspi->regmap_pushr, PUSHR_TX, txdata);
+ regmap_write(dspi->regmap_pushr, dspi->pushr_tx, txdata);
}

static void dspi_xspi_write(struct fsl_dspi *dspi, int cnt, bool eoq)
@@ -1259,6 +1262,7 @@ static int dspi_probe(struct platform_device *pdev)
struct fsl_dspi *dspi;
struct resource *res;
void __iomem *base;
+ bool big_endian;

ctlr = spi_alloc_master(&pdev->dev, sizeof(struct fsl_dspi));
if (!ctlr)
@@ -1284,6 +1288,7 @@ static int dspi_probe(struct platform_device *pdev)

/* Only Coldfire uses platform data */
dspi->devtype_data = &devtype_data[MCF5441X];
+ big_endian = true;
} else {

ret = of_property_read_u32(np, "spi-num-chipselects", &cs_num);
@@ -1305,6 +1310,15 @@ static int dspi_probe(struct platform_device *pdev)
ret = -EFAULT;
goto out_ctlr_put;
}
+
+ big_endian = of_device_is_big_endian(np);
+ }
+ if (big_endian) {
+ dspi->pushr_cmd = 0;
+ dspi->pushr_tx = 2;
+ } else {
+ dspi->pushr_cmd = 2;
+ dspi->pushr_tx = 0;
}

if (dspi->devtype_data->trans_mode == DSPI_XSPI_MODE)
--
2.17.1
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