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spi/spi_sh_msiof: consolidate data in 8-bit mode into 32-bit words

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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: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Guennadi Liakhovetski 2011-01-21 16:56:42 +01:00 committed by Grant Likely
parent e2dbf5ebcc
commit 9dabb3f326
1 changed files with 59 additions and 0 deletions
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59
drivers/spi/spi_sh_msiof.c
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@ -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)