[U-Boot] [PATCH 2/2] EXYNOS: SPI: Support SPI_PREAMBLE mode
Simon Glass
sjg at chromium.org
Mon May 6 14:06:24 CEST 2013
Hi Vadim,
On Thu, May 2, 2013 at 7:28 PM, Vadim Bendebury <vbendeb at chromium.org> wrote:
> On Thu, Mar 21, 2013 at 11:29 PM, Rajeshwari Shinde
> <rajeshwari.s at samsung.com> wrote:
>> 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 at chromium.org>
>> Signed-off-by: Rajeshwari Shinde <rajeshwari.s at samsung.com>
>> ---
>> drivers/spi/exynos_spi.c | 62 ++++++++++++++++++++++++++++++++++++++++------
>> 1 files changed, 54 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c
>> index be60ada..09e88d5 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)
>> @@ -107,6 +108,8 @@ 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);
>> @@ -219,17 +222,23 @@ static void spi_request_bytes(struct exynos_spi *regs, int count)
>> writel(count | SPI_PACKET_CNT_EN, ®s->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, preamable_count = 0;
>
> preamable_count: the name is misspelled, and the variable is never modified.
>
>> + 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.
>> @@ -240,6 +249,7 @@ 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;
>> while (in_bytes) {
>> int temp;
>>
>> @@ -252,13 +262,41 @@ static void spi_rx_tx(struct exynos_spi_slave *spi_slave, int todo,
>> }
>> if (rx_lvl > 0 && in_bytes) {
>> temp = readl(®s->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--;
>> + }
>> + /*
>> + * 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.
>> + */
>> + else if (in_bytes && !toread) {
>> + assert(!out_bytes);
>> + toread = out_bytes = 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);
>> + printf("count = %d\n", preamable_count);
>> + return -1;
>> }
>> }
>> *dinp = rxp;
>> *doutp = txp;
>> + return 0;
>> }
>>
>> /**
>> @@ -278,6 +316,7 @@ 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) {
>> @@ -291,16 +330,22 @@ 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);
>> }
>>
>> /* 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;
>> }
>>
>> /**
>> @@ -327,6 +372,7 @@ 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;
>
> who sets this bit in the 'mode' field?
This is set by whoever creates the slave - in the case of snow it is cros_ec.
Regards,
Simon
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