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Subject[PATCH 2/6] 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 define the
offsets per-instantiation, in the devtype_data structure. This means
that we have to know from the driver which controllers are big- and
which are little-endian (which is fine, we do, but it makes the device
tree binding itself a little redundant except for regmap_config).

This patch does not apply cleanly to stable trees, and a punctual fix to
the commit cannot be provided given this constraint of lack of access to
regmap_get_val_endian(). The per-SoC devtype_data structures (and
therefore the premises to fix this bug) have been introduced only a few
commits ago, in commit d35054010b57 ("spi: spi-fsl-dspi: Use specific
compatible strings for all SoC instantiations")

Fixes: 58ba07ec79e6 ("spi: spi-fsl-dspi: Add support for XSPI mode registers")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
drivers/spi/spi-fsl-dspi.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 0ce26c1cbf62..a8e56abe20ac 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 {
@@ -124,6 +120,12 @@ struct fsl_dspi_devtype_data {
u8 max_clock_factor;
int fifo_size;
int dma_bufsize;
+ /*
+ * Offsets for CMD and TXDATA within SPI_PUSHR when accessed
+ * individually (in XSPI mode)
+ */
+ int pushr_cmd;
+ int pushr_tx;
};

enum {
@@ -150,42 +152,56 @@ static const struct fsl_dspi_devtype_data devtype_data[] = {
.trans_mode = DSPI_XSPI_MODE,
.max_clock_factor = 8,
.fifo_size = 4,
+ .pushr_cmd = 0,
+ .pushr_tx = 2,
},
[LS1012A] = {
/* Has A-011218 DMA erratum */
.trans_mode = DSPI_XSPI_MODE,
.max_clock_factor = 8,
.fifo_size = 16,
+ .pushr_cmd = 0,
+ .pushr_tx = 2,
},
[LS1043A] = {
/* Has A-011218 DMA erratum */
.trans_mode = DSPI_XSPI_MODE,
.max_clock_factor = 8,
.fifo_size = 16,
+ .pushr_cmd = 0,
+ .pushr_tx = 2,
},
[LS1046A] = {
/* Has A-011218 DMA erratum */
.trans_mode = DSPI_XSPI_MODE,
.max_clock_factor = 8,
.fifo_size = 16,
+ .pushr_cmd = 0,
+ .pushr_tx = 2,
},
[LS2080A] = {
.trans_mode = DSPI_DMA_MODE,
.dma_bufsize = 8,
.max_clock_factor = 8,
.fifo_size = 4,
+ .pushr_cmd = 2,
+ .pushr_tx = 0,
},
[LS2085A] = {
.trans_mode = DSPI_DMA_MODE,
.dma_bufsize = 8,
.max_clock_factor = 8,
.fifo_size = 4,
+ .pushr_cmd = 2,
+ .pushr_tx = 0,
},
[LX2160A] = {
.trans_mode = DSPI_DMA_MODE,
.dma_bufsize = 8,
.max_clock_factor = 8,
.fifo_size = 4,
+ .pushr_cmd = 2,
+ .pushr_tx = 0,
},
[MCF5441X] = {
.trans_mode = DSPI_EOQ_MODE,
@@ -670,12 +686,12 @@ 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->devtype_data->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->devtype_data->pushr_tx, txdata);
}

static void dspi_xspi_write(struct fsl_dspi *dspi, int cnt, bool eoq)
--
2.17.1
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