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Unverified Commit 2801b2f5 authored by Maxime Chevallier's avatar Maxime Chevallier Committed by Mark Brown
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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: default avatarMaxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent a021cac4

drivers/spi/spi-imx.c

+9 −14
Original line number Diff line number Diff line
@@ -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;