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Date: Mon, 09 Mar 2020 18:59:04 +0100
From: Michael Walle <michael@...le.cc>
To: Vladimir Oltean <olteanv@...il.com>
Cc: broonie@...nel.org, linux-spi@...r.kernel.org,
linux-kernel@...r.kernel.org, shawnguo@...nel.org,
robh+dt@...nel.org, mark.rutland@....com,
devicetree@...r.kernel.org, eha@...f.com, angelo@...am.it,
andrew.smirnov@...il.com, gustavo@...eddedor.com, weic@...dia.com,
mhosny@...dia.com, peng.ma@....com
Subject: Re: [PATCH 2/6] spi: spi-fsl-dspi: Fix little endian access to PUSHR
CMD and TXDATA
Am 2020-03-09 15:56, schrieb Vladimir Oltean:
> From: Vladimir Oltean <vladimir.oltean@....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@....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;
> };
Shouldn't this just read the "little-endian" property of the
device tree node? Like it worked before with regmap, which takes
the little-endian/big-endian property into account.
If I understand this correctly, this solution would mix the methods
how the IP endianess is determined. Eg. regmap_xx uses the
little-endian property and this driver then also uses the compatible
string to also distinguish between the endianess.
-michael
> 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)
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