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Commit 9dabb3f3 authored by Guennadi Liakhovetski's avatar Guennadi Liakhovetski Committed by Grant Likely
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spi/spi_sh_msiof: consolidate data in 8-bit mode into 32-bit words 



Instead of sending data 8 bits at a time in 8-bit SPI mode, swap bytes
and send and receive them 32 bits at a time. Tested with an SD-card,
with which this patch reduced the number of interrupts by 50%, when
reading 5MiB of data (there are also small service packets, the number
of interrupts, produced by 512-byte sectors should, of course, drop by
75%), and improved throughput by more than 40%.

Signed-off-by: default avatarGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent e2dbf5eb

drivers/spi/spi_sh_msiof.c

+59 −0
Original line number Diff line number Diff line
@@ -267,6 +267,26 @@ static void sh_msiof_spi_write_fifo_32u(struct sh_msiof_spi_priv *p, 
		sh_msiof_write(p, TFDR, get_unaligned(&buf_32[k]) << fs);

}



static void sh_msiof_spi_write_fifo_s32(struct sh_msiof_spi_priv *p,

					const void *tx_buf, int words, int fs)

{

	const u32 *buf_32 = tx_buf;

	int k;



	for (k = 0; k < words; k++)

		sh_msiof_write(p, TFDR, swab32(buf_32[k] << fs));

}



static void sh_msiof_spi_write_fifo_s32u(struct sh_msiof_spi_priv *p,

					 const void *tx_buf, int words, int fs)

{

	const u32 *buf_32 = tx_buf;

	int k;



	for (k = 0; k < words; k++)

		sh_msiof_write(p, TFDR, swab32(get_unaligned(&buf_32[k]) << fs));

}



static void sh_msiof_spi_read_fifo_8(struct sh_msiof_spi_priv *p,

				     void *rx_buf, int words, int fs)

{
@@ -317,6 +337,26 @@ static void sh_msiof_spi_read_fifo_32u(struct sh_msiof_spi_priv *p, 
		put_unaligned(sh_msiof_read(p, RFDR) >> fs, &buf_32[k]);

}



static void sh_msiof_spi_read_fifo_s32(struct sh_msiof_spi_priv *p,

				       void *rx_buf, int words, int fs)

{

	u32 *buf_32 = rx_buf;

	int k;



	for (k = 0; k < words; k++)

		buf_32[k] = swab32(sh_msiof_read(p, RFDR) >> fs);

}



static void sh_msiof_spi_read_fifo_s32u(struct sh_msiof_spi_priv *p,

				       void *rx_buf, int words, int fs)

{

	u32 *buf_32 = rx_buf;

	int k;



	for (k = 0; k < words; k++)

		put_unaligned(swab32(sh_msiof_read(p, RFDR) >> fs), &buf_32[k]);

}



static int sh_msiof_spi_bits(struct spi_device *spi, struct spi_transfer *t)

{

	int bits;
@@ -468,9 +508,17 @@ static int sh_msiof_spi_txrx(struct spi_device *spi, struct spi_transfer *t) 
	int bytes_done;

	int words;

	int n;

	bool swab;



	bits = sh_msiof_spi_bits(spi, t);



	if (bits <= 8 && t->len > 15 && !(t->len & 3)) {

		bits = 32;

		swab = true;

	} else {

		swab = false;

	}



	/* setup bytes per word and fifo read/write functions */

	if (bits <= 8) {

		bytes_per_word = 1;
@@ -487,6 +535,17 @@ static int sh_msiof_spi_txrx(struct spi_device *spi, struct spi_transfer *t) 
			rx_fifo = sh_msiof_spi_read_fifo_16u;

		else

			rx_fifo = sh_msiof_spi_read_fifo_16;

	} else if (swab) {

		bytes_per_word = 4;

		if ((unsigned long)t->tx_buf & 0x03)

			tx_fifo = sh_msiof_spi_write_fifo_s32u;

		else

			tx_fifo = sh_msiof_spi_write_fifo_s32;



		if ((unsigned long)t->rx_buf & 0x03)

			rx_fifo = sh_msiof_spi_read_fifo_s32u;

		else

			rx_fifo = sh_msiof_spi_read_fifo_s32;

	} else {

		bytes_per_word = 4;

		if ((unsigned long)t->tx_buf & 0x03)