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spi: imx: Use dynamic bursts only when bits_per_word is 8, 16 or 32 

The dynamic bursts mode allows to group together multiple words into a
single burst. To do so, it's necessary that words can be packed into the
32-bits FIFO entries, so we can't allow using this mode with bit_per_words
different to 8, 16 or 32.

This prevents shitfing out extra clock ticks for transfers with
bit_per_word values not aligned on 8 bits.

With that , we are sure that only the correct number of bits is
shifted out at each transfer, so we don't need to mask out the remaining
parts of the words.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Maxime Chevallier 2018-07-17 16:31:51 +02:00 committed by Mark Brown
parent a021cac420
commit 2801b2f5fa
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 9 additions and 14 deletions
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23
drivers/spi/spi-imx.c
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@ -95,7 +95,6 @@ struct spi_imx_data {
const void *tx_buf;
unsigned int txfifo; /* number of words pushed in tx FIFO */
unsigned int dynamic_burst, read_u32;
unsigned int word_mask;
/* Slave mode */
bool slave_mode;
@ -291,7 +290,6 @@ static void spi_imx_buf_rx_swap_u32(struct spi_imx_data *spi_imx)
else if (bytes_per_word == 2)
val = (val << 16) | (val >> 16);
#endif
val &= spi_imx->word_mask;
*(u32 *)spi_imx->rx_buf = val;
spi_imx->rx_buf += sizeof(u32);
}
@ -322,7 +320,6 @@ static void spi_imx_buf_tx_swap_u32(struct spi_imx_data *spi_imx)
if (spi_imx->tx_buf) {
val = *(u32 *)spi_imx->tx_buf;
val &= spi_imx->word_mask;
spi_imx->tx_buf += sizeof(u32);
}
@ -1102,25 +1099,23 @@ static int spi_imx_setupxfer(struct spi_device *spi,
spi_imx->bits_per_word = t->bits_per_word;
spi_imx->speed_hz = t->speed_hz;
/* Initialize the functions for transfer */
if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode) {
u32 mask;
/*
* Initialize the functions for transfer. To transfer non byte-aligned
* words, we have to use multiple word-size bursts, we can't use
* dynamic_burst in that case.
*/
if (spi_imx->devtype_data->dynamic_burst && !spi_imx->slave_mode &&
(spi_imx->bits_per_word == 8 ||
spi_imx->bits_per_word == 16 ||
spi_imx->bits_per_word == 32)) {
spi_imx->read_u32 = 1;
mask = (1 << spi_imx->bits_per_word) - 1;
spi_imx->rx = spi_imx_buf_rx_swap;
spi_imx->tx = spi_imx_buf_tx_swap;
spi_imx->dynamic_burst = 1;
spi_imx->remainder = t->len;
if (spi_imx->bits_per_word <= 8)
spi_imx->word_mask = mask << 24 | mask << 16
| mask << 8 | mask;
else if (spi_imx->bits_per_word <= 16)
spi_imx->word_mask = mask << 16 | mask;
else
spi_imx->word_mask = mask;
} else {
if (spi_imx->bits_per_word <= 8) {
spi_imx->rx = spi_imx_buf_rx_u8;