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spi: exynos: Support SPI_PREAMBLE mode

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Support interfaces with a preamble before each received message.

We handle this when the client has requested a SPI_XFER_END, meaning
that we must close of the transaction. In this case we read until we
see the preamble (or a timeout occurs), skipping all data before and
including the preamble. The client will receive only data bytes after
the preamble.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
This commit is contained in:
Rajeshwari Shinde 2013-05-28 20:10:38 +00:00 committed by Jagannadha Sutradharudu Teki
parent bb786b84bd
commit e4eaef8910
1 changed files with 59 additions and 10 deletions
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69
drivers/spi/exynos_spi.c
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@ -51,6 +51,7 @@ struct exynos_spi_slave {
unsigned int mode;
enum periph_id periph_id; /* Peripheral ID for this device */
unsigned int fifo_size;
int skip_preamble;
};
static struct spi_bus *spi_get_bus(unsigned dev_index)
@ -105,6 +106,8 @@ struct spi_slave *spi_setup_slave(unsigned int busnum, unsigned int cs,
else
spi_slave->fifo_size = 256;
spi_slave->skip_preamble = 0;
spi_slave->freq = bus->frequency;
if (max_hz)
spi_slave->freq = min(max_hz, spi_slave->freq);
@ -217,17 +220,23 @@ static void spi_request_bytes(struct exynos_spi *regs, int count)
writel(count | SPI_PACKET_CNT_EN, &regs->pkt_cnt);
}
static void spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
void **dinp, void const **doutp)
static int spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
void **dinp, void const **doutp, unsigned long flags)
{
struct exynos_spi *regs = spi_slave->regs;
uchar *rxp = *dinp;
const uchar *txp = *doutp;
int rx_lvl, tx_lvl;
uint out_bytes, in_bytes;
int toread;
unsigned start = get_timer(0);
int stopping;
out_bytes = in_bytes = todo;
stopping = spi_slave->skip_preamble && (flags & SPI_XFER_END) &&
!(spi_slave->mode & SPI_SLAVE);
/*
* If there's something to send, do a software reset and set a
* transaction size.
@ -238,6 +247,8 @@ static void spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
* Bytes are transmitted/received in pairs. Wait to receive all the
* data because then transmission will be done as well.
*/
toread = in_bytes;
while (in_bytes) {
int temp;
@ -248,15 +259,43 @@ static void spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
writel(temp, &regs->tx_data);
out_bytes--;
}
if (rx_lvl > 0 && in_bytes) {
if (rx_lvl > 0) {
temp = readl(&regs->rx_data);
if (rxp)
*rxp++ = temp;
in_bytes--;
if (spi_slave->skip_preamble) {
if (temp == SPI_PREAMBLE_END_BYTE) {
spi_slave->skip_preamble = 0;
stopping = 0;
}
} else {
if (rxp || stopping)
*rxp++ = temp;
in_bytes--;
}
toread--;
} else if (!toread) {
/*
* We have run out of input data, but haven't read
* enough bytes after the preamble yet. Read some more,
* and make sure that we transmit dummy bytes too, to
* keep things going.
*/
assert(!out_bytes);
out_bytes = in_bytes;
toread = in_bytes;
txp = NULL;
spi_request_bytes(regs, toread);
}
if (spi_slave->skip_preamble && get_timer(start) > 100) {
printf("SPI timeout: in_bytes=%d, out_bytes=%d, ",
in_bytes, out_bytes);
return -1;
}
}
*dinp = rxp;
*doutp = txp;
return 0;
}
/**
@ -276,6 +315,7 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
struct exynos_spi_slave *spi_slave = to_exynos_spi(slave);
int upto, todo;
int bytelen;
int ret = 0;
/* spi core configured to do 8 bit transfers */
if (bitlen % 8) {
@ -289,16 +329,24 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
/* Exynos SPI limits each transfer to 65535 bytes */
bytelen = bitlen / 8;
for (upto = 0; upto < bytelen; upto += todo) {
for (upto = 0; !ret && upto < bytelen; upto += todo) {
todo = min(bytelen - upto, (1 << 16) - 1);
spi_rx_tx(spi_slave, todo, &din, &dout);
ret = spi_rx_tx(spi_slave, todo, &din, &dout, flags);
if (ret)
break;
}
/* Stop the transaction, if necessary. */
if ((flags & SPI_XFER_END))
if ((flags & SPI_XFER_END) && !(spi_slave->mode & SPI_SLAVE)) {
spi_cs_deactivate(slave);
if (spi_slave->skip_preamble) {
assert(!spi_slave->skip_preamble);
debug("Failed to complete premable transaction\n");
ret = -1;
}
}
return 0;
return ret;
}
/**
@ -325,6 +373,7 @@ void spi_cs_activate(struct spi_slave *slave)
clrbits_le32(&spi_slave->regs->cs_reg, SPI_SLAVE_SIG_INACT);
debug("Activate CS, bus %d\n", spi_slave->slave.bus);
spi_slave->skip_preamble = spi_slave->mode & SPI_PREAMBLE;
}
/**