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spi: armada-3700: Fix padding when sending not 4-byte aligned data
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In 4-byte transfer mode, extra padding/dummy bytes '0xff' would be
sent in write operation if TX data is not 4-byte aligned since the
SPI data register is always shifted out as whole 4 bytes.

Fix this by using the header count feature that allows to transfer 0 to
4 bytes. Use it to actually send the first 1 to 3 bytes of data before
the rest of the buffer that will hence be 4-byte aligned.

Signed-off-by: Zachary Zhang <zhangzg@marvell.com>
Signed-off-by: Miquel Raynal <miquel.raynal@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
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Zachary Zhang authored and Mark Brown committed Sep 13, 2017
1 parent 747e1f6 commit 6fd6fd6
Showing 1 changed file with 41 additions and 94 deletions.
135 changes: 41 additions & 94 deletions drivers/spi/spi-armada-3700.c
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Original file line number Diff line number Diff line change
Expand Up @@ -99,11 +99,6 @@
/* A3700_SPI_IF_TIME_REG */
#define A3700_SPI_CLK_CAPT_EDGE BIT(7)

/* Flags and macros for struct a3700_spi */
#define A3700_INSTR_CNT 1
#define A3700_ADDR_CNT 3
#define A3700_DUMMY_CNT 1

struct a3700_spi {
struct spi_master *master;
void __iomem *base;
Expand All @@ -117,9 +112,6 @@ struct a3700_spi {
u8 byte_len;
u32 wait_mask;
struct completion done;
u32 addr_cnt;
u32 instr_cnt;
size_t hdr_cnt;
};

static u32 spireg_read(struct a3700_spi *a3700_spi, u32 offset)
Expand Down Expand Up @@ -449,59 +441,43 @@ static void a3700_spi_set_cs(struct spi_device *spi, bool enable)

static void a3700_spi_header_set(struct a3700_spi *a3700_spi)
{
u32 instr_cnt = 0, addr_cnt = 0, dummy_cnt = 0;
unsigned int addr_cnt;
u32 val = 0;

/* Clear the header registers */
spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, 0);
spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, 0);
spireg_write(a3700_spi, A3700_SPI_IF_RMODE_REG, 0);
spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, 0);

/* Set header counters */
if (a3700_spi->tx_buf) {
if (a3700_spi->buf_len <= a3700_spi->instr_cnt) {
instr_cnt = a3700_spi->buf_len;
} else if (a3700_spi->buf_len <= (a3700_spi->instr_cnt +
a3700_spi->addr_cnt)) {
instr_cnt = a3700_spi->instr_cnt;
addr_cnt = a3700_spi->buf_len - instr_cnt;
} else if (a3700_spi->buf_len <= a3700_spi->hdr_cnt) {
instr_cnt = a3700_spi->instr_cnt;
addr_cnt = a3700_spi->addr_cnt;
/* Need to handle the normal write case with 1 byte
* data
*/
if (!a3700_spi->tx_buf[instr_cnt + addr_cnt])
dummy_cnt = a3700_spi->buf_len - instr_cnt -
addr_cnt;
/*
* when tx data is not 4 bytes aligned, there will be unexpected
* bytes out of SPI output register, since it always shifts out
* as whole 4 bytes. This might cause incorrect transaction with
* some devices. To avoid that, use SPI header count feature to
* transfer up to 3 bytes of data first, and then make the rest
* of data 4-byte aligned.
*/
addr_cnt = a3700_spi->buf_len % 4;
if (addr_cnt) {
val = (addr_cnt & A3700_SPI_ADDR_CNT_MASK)
<< A3700_SPI_ADDR_CNT_BIT;
spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);

/* Update the buffer length to be transferred */
a3700_spi->buf_len -= addr_cnt;

/* transfer 1~3 bytes through address count */
val = 0;
while (addr_cnt--) {
val = (val << 8) | a3700_spi->tx_buf[0];
a3700_spi->tx_buf++;
}
spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, val);
}
val |= ((instr_cnt & A3700_SPI_INSTR_CNT_MASK)
<< A3700_SPI_INSTR_CNT_BIT);
val |= ((addr_cnt & A3700_SPI_ADDR_CNT_MASK)
<< A3700_SPI_ADDR_CNT_BIT);
val |= ((dummy_cnt & A3700_SPI_DUMMY_CNT_MASK)
<< A3700_SPI_DUMMY_CNT_BIT);
}
spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);

/* Update the buffer length to be transferred */
a3700_spi->buf_len -= (instr_cnt + addr_cnt + dummy_cnt);

/* Set Instruction */
val = 0;
while (instr_cnt--) {
val = (val << 8) | a3700_spi->tx_buf[0];
a3700_spi->tx_buf++;
}
spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, val);

/* Set Address */
val = 0;
while (addr_cnt--) {
val = (val << 8) | a3700_spi->tx_buf[0];
a3700_spi->tx_buf++;
}
spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, val);
}

static int a3700_is_wfifo_full(struct a3700_spi *a3700_spi)
Expand All @@ -515,35 +491,12 @@ static int a3700_is_wfifo_full(struct a3700_spi *a3700_spi)
static int a3700_spi_fifo_write(struct a3700_spi *a3700_spi)
{
u32 val;
int i = 0;

while (!a3700_is_wfifo_full(a3700_spi) && a3700_spi->buf_len) {
val = 0;
if (a3700_spi->buf_len >= 4) {
val = cpu_to_le32(*(u32 *)a3700_spi->tx_buf);
spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);

a3700_spi->buf_len -= 4;
a3700_spi->tx_buf += 4;
} else {
/*
* If the remained buffer length is less than 4-bytes,
* we should pad the write buffer with all ones. So that
* it avoids overwrite the unexpected bytes following
* the last one.
*/
val = GENMASK(31, 0);
while (a3700_spi->buf_len) {
val &= ~(0xff << (8 * i));
val |= *a3700_spi->tx_buf++ << (8 * i);
i++;
a3700_spi->buf_len--;

spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG,
val);
}
break;
}
val = cpu_to_le32(*(u32 *)a3700_spi->tx_buf);
spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);
a3700_spi->buf_len -= 4;
a3700_spi->tx_buf += 4;
}

return 0;
Expand Down Expand Up @@ -648,16 +601,19 @@ static int a3700_spi_transfer_one(struct spi_master *master,
a3700_spi->rx_buf = xfer->rx_buf;
a3700_spi->buf_len = xfer->len;

/* SPI transfer headers */
a3700_spi_header_set(a3700_spi);

if (xfer->tx_buf)
nbits = xfer->tx_nbits;
else if (xfer->rx_buf)
nbits = xfer->rx_nbits;

a3700_spi_pin_mode_set(a3700_spi, nbits, xfer->rx_buf ? true : false);

/* Flush the FIFOs */
a3700_spi_fifo_flush(a3700_spi);

/* Transfer first bytes of data when buffer is not 4-byte aligned */
a3700_spi_header_set(a3700_spi);

if (xfer->rx_buf) {
/* Set read data length */
spireg_write(a3700_spi, A3700_SPI_IF_DIN_CNT_REG,
Expand Down Expand Up @@ -736,16 +692,11 @@ static int a3700_spi_transfer_one(struct spi_master *master,
dev_err(&spi->dev, "wait wfifo empty timed out\n");
return -ETIMEDOUT;
}
} else {
/*
* If the instruction in SPI_INSTR does not require data
* to be written to the SPI device, wait until SPI_RDY
* is 1 for the SPI interface to be in idle.
*/
if (!a3700_spi_transfer_wait(spi, A3700_SPI_XFER_RDY)) {
dev_err(&spi->dev, "wait xfer ready timed out\n");
return -ETIMEDOUT;
}
}

if (!a3700_spi_transfer_wait(spi, A3700_SPI_XFER_RDY)) {
dev_err(&spi->dev, "wait xfer ready timed out\n");
return -ETIMEDOUT;
}

val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
Expand Down Expand Up @@ -837,10 +788,6 @@ static int a3700_spi_probe(struct platform_device *pdev)
memset(spi, 0, sizeof(struct a3700_spi));

spi->master = master;
spi->instr_cnt = A3700_INSTR_CNT;
spi->addr_cnt = A3700_ADDR_CNT;
spi->hdr_cnt = A3700_INSTR_CNT + A3700_ADDR_CNT +
A3700_DUMMY_CNT;

res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
spi->base = devm_ioremap_resource(dev, res);
Expand Down

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