[U-Boot] [U-Boot, 2/2, V5] spi: exynos: Support SPI_PREAMBLE mode

[Jagan Teki]

On 29-05-2013 01:40, Rajeshwari Shinde 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>
>
> ---
> Changes in V2:
> 	- Remove preamable_count variable which is not really needed
> 	- Fix checkpatch warning (multiple assignments)
> Changes in V3:
> 	- Modified the if logic in spi_rx_tx function
> 	- Added blank lines as suggested by Minkyu Kang.
> 	- Removed in_bytes check in while loop.
> 	- Added a error check.
> Changes in V4:
> 	- Corrected a if condition.
> Changes in V5:
> 	- In commit message header changed EXYNOS: SPI: to spi:exynos.
>   drivers/spi/exynos_spi.c |   69 +++++++++++++++++++++++++++++++++++++++------
>   1 files changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c
> index 607e1cd..01378d0 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 +247,8 @@ 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;
>   }
>   
>   /**
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki at gmail.com>

--
Thanks,
Jagan.