Re: [U-Boot] [PATCH v2] EXYNOS: SPI: Support SPI_PREAMBLE mode

Dear Rajeshwari Shinde,

On 12/05/13 00:04, Simon Glass wrote:

From: Rajeshwari Shinde rajeshwari.s@samsung.com

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

---

Changes in v2:

• Remove preamable_count variable which is not really needed
• Fix checkpatch warning (multiple assignments)

drivers/spi/exynos_spi.c | 62 +++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 54 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c index 607e1cd..b7b2ea5 100644 --- a/drivers/spi/exynos_spi.c +++ b/drivers/spi/exynos_spi.c @@ -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 +247,7 @@ 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;

please add blank line here.

while (in_bytes) { int temp;

@@ -250,13 +260,41 @@ static void spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo, } if (rx_lvl > 0 && in_bytes) {

I think, in_bytes is always true. It's a redundant checking.

	temp = readl(&regs->rx_data);

• 	if (rxp)
  

• 	if (!rxp && !stopping) {
  

• 		in_bytes--;
  

• 	} else if (spi_slave->skip_preamble) {
  

• 		if (temp == SPI_PREAMBLE_END_BYTE) {
  

• 			spi_slave->skip_preamble = 0;
  

• 			stopping = 0;
  

• 		}
  

• 	} else {
  	*rxp++ = temp;
  

• 	in_bytes--;
  

• 		in_bytes--;
  

• 	}
  

• 	toread--;
  

• }
  

I think, this if statement is not logical. The checking condition is differ, so it looks confused.

How about this?

+ temp = readl(&regs->rx_data); + 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--;

• /*
  

•  * 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.
  

•  */
  

This comment is what for? please move this comment into the brace.

• else if (in_bytes && !toread) {
  

in_bytes.. ditto.

And please fix brace. } else if (

• 	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;

please add blank line here.

• return 0;

}

/** @@ -276,6 +314,7 @@ 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 +328,22 @@ 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);
  

It looks good. But I think, it's better to checking the error explicitly.

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 +370,7 @@ 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;

}

/**

Thanks, Minkyu Kang.