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SubjectRe: [PATCH RESEND 2/5] spi: imx: Use dynamic bursts only when bits_per_word is 8, 16 or 32
On Tue, Jul 17, 2018 at 04:31:51PM +0200, Maxime Chevallier wrote:
> 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

s/shitfing/shifting/

> 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>

Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>

Sascha

> ---
> drivers/spi/spi-imx.c | 23 +++++++++--------------
> 1 file changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index d75153c995af..ecafbda5ec94 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -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;
> --
> 2.11.0
>
>

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