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spi: exynos: Support word transfers

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Since SPI register access is so expensive, it is worth transferring data
a word at a time if we can. This complicates the driver unfortunately.

Use the byte-swapping feature to avoid having to convert to/from big
endian in software.

This change increases speed from about 2MB/s to about 4.5MB/s.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rajeshwari S Shinde <rajeshwari.s@samsung.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
This commit is contained in:
Rajeshwari Shinde 2013-10-08 16:20:06 +05:30 committed by Jagannadha Sutradharudu Teki
parent 120af1572a
commit c4a796329d
2 changed files with 71 additions and 16 deletions
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11
arch/arm/include/asm/arch-exynos/spi.h
View File

@ -22,7 +22,7 @@ struct exynos_spi {
unsigned int rx_data; /* 0x1c */
unsigned int pkt_cnt; /* 0x20 */
unsigned char reserved2[4];
unsigned char reserved3[4];
unsigned int swap_cfg; /* 0x28 */
unsigned int fb_clk; /* 0x2c */
unsigned char padding[0xffd0];
};
@ -62,5 +62,14 @@ struct exynos_spi {
/* Packet Count */
#define SPI_PACKET_CNT_EN (1 << 16)
/* Swap config */
#define SPI_TX_SWAP_EN (1 << 0)
#define SPI_TX_BYTE_SWAP (1 << 2)
#define SPI_TX_HWORD_SWAP (1 << 3)
#define SPI_TX_BYTE_SWAP (1 << 2)
#define SPI_RX_SWAP_EN (1 << 4)
#define SPI_RX_BYTE_SWAP (1 << 6)
#define SPI_RX_HWORD_SWAP (1 << 7)
#endif /* __ASSEMBLY__ */
#endif

76
drivers/spi/exynos_spi.c
View File

@ -204,12 +204,29 @@ static void spi_get_fifo_levels(struct exynos_spi *regs,
*
* @param regs SPI peripheral registers
* @param count Number of bytes to transfer
* @param step Number of bytes to transfer in each packet (1 or 4)
*/
static void spi_request_bytes(struct exynos_spi *regs, int count)
static void spi_request_bytes(struct exynos_spi *regs, int count, int step)
{
/* For word address we need to swap bytes */
if (step == 4) {
setbits_le32(&regs->mode_cfg,
SPI_MODE_CH_WIDTH_WORD | SPI_MODE_BUS_WIDTH_WORD);
count /= 4;
setbits_le32(&regs->swap_cfg, SPI_TX_SWAP_EN | SPI_RX_SWAP_EN |
SPI_TX_BYTE_SWAP | SPI_RX_BYTE_SWAP |
SPI_TX_HWORD_SWAP | SPI_RX_HWORD_SWAP);
} else {
/* Select byte access and clear the swap configuration */
clrbits_le32(&regs->mode_cfg,
SPI_MODE_CH_WIDTH_WORD | SPI_MODE_BUS_WIDTH_WORD);
writel(0, &regs->swap_cfg);
}
assert(count && count < (1 << 16));
setbits_le32(&regs->ch_cfg, SPI_CH_RST);
clrbits_le32(&regs->ch_cfg, SPI_CH_RST);
writel(count | SPI_PACKET_CNT_EN, &regs->pkt_cnt);
}
@ -224,17 +241,27 @@ static int spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
int toread;
unsigned start = get_timer(0);
int stopping;
int step;
out_bytes = in_bytes = todo;
stopping = spi_slave->skip_preamble && (flags & SPI_XFER_END) &&
!(spi_slave->mode & SPI_SLAVE);
/*
* Try to transfer words if we can. This helps read performance at
* SPI clock speeds above about 20MHz.
*/
step = 1;
if (!((todo | (uintptr_t)rxp | (uintptr_t)txp) & 3) &&
!spi_slave->skip_preamble)
step = 4;
/*
* If there's something to send, do a software reset and set a
* transaction size.
*/
spi_request_bytes(regs, todo);
spi_request_bytes(regs, todo, step);
/*
* Bytes are transmitted/received in pairs. Wait to receive all the
@ -247,14 +274,26 @@ static int spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
/* Keep the fifos full/empty. */
spi_get_fifo_levels(regs, &rx_lvl, &tx_lvl);
/*
* Don't completely fill the txfifo, since we don't want our
* rxfifo to overflow, and it may already contain data.
*/
while (tx_lvl < spi_slave->fifo_size/2 && out_bytes) {
temp = txp ? *txp++ : 0xff;
if (!txp)
temp = -1;
else if (step == 4)
temp = *(uint32_t *)txp;
else
temp = *txp;
writel(temp, &regs->tx_data);
out_bytes--;
tx_lvl++;
out_bytes -= step;
if (txp)
txp += step;
tx_lvl += step;
}
if (rx_lvl > 0) {
while (rx_lvl > 0) {
if (rx_lvl >= step) {
while (rx_lvl >= step) {
temp = readl(&regs->rx_data);
if (spi_slave->skip_preamble) {
if (temp == SPI_PREAMBLE_END_BYTE) {
@ -262,12 +301,15 @@ static int spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
stopping = 0;
}
} else {
if (rxp || stopping)
*rxp++ = temp;
in_bytes--;
if (rxp || stopping) {
*rxp = temp;
rxp += step;
}
in_bytes -= step;
}
toread--;
rx_lvl--;
toread -= step;
rx_lvl -= step;
}
} else if (!toread) {
/*
* We have run out of input data, but haven't read
@ -279,7 +321,7 @@ static int spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
out_bytes = in_bytes;
toread = in_bytes;
txp = NULL;
spi_request_bytes(regs, toread);
spi_request_bytes(regs, toread, step);
}
if (spi_slave->skip_preamble && get_timer(start) > 100) {
printf("SPI timeout: in_bytes=%d, out_bytes=%d, ",
@ -323,10 +365,14 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
if ((flags & SPI_XFER_BEGIN))
spi_cs_activate(slave);
/* Exynos SPI limits each transfer to 65535 bytes */
/*
* Exynos SPI limits each transfer to 65535 transfers. To keep
* things simple, allow a maximum of 65532 bytes. We could allow
* more in word mode, but the performance difference is small.
*/
bytelen = bitlen / 8;
for (upto = 0; !ret && upto < bytelen; upto += todo) {
todo = min(bytelen - upto, (1 << 16) - 1);
todo = min(bytelen - upto, (1 << 16) - 4);
ret = spi_rx_tx(spi_slave, todo, &din, &dout, flags);
if (ret)
break;