[U-Boot] [PATCH 2/2 V3] spi: exynos: Support a delay after deactivate

[Jagan Teki]

Hi,

On 30-05-2013 10:49, Rajeshwari Shinde wrote:
> For devices that need some time to react after a spi transaction
> finishes, add the ability to set a delay.
>
> Implement this as a delay on the first/next transaction to avoid
> any delay in the fairly common case where a SPI transaction is
> followed by other processing.
>
> Based on:
> "[U-Boot] [PATCH 0/2 V5] spi: Enable SPI_PREAMBLE Mode"

Please use the below format for referring previous commits
ex:
"<PREVIOUS_COMMIT_HEAD>"
(sha1: PREVIOUS_COMMIT_ID)

in this case
"spi: exynos: Support SPI_PREAMBLE mode"
(sha1: e4eaef8910df805d511b1cb9b2caafa7d2827fdc)

>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Signed-off-by: Rajeshwari Shinde <rajeshwari.s at samsung.com>
> ---
> Changes in V2:
> 	- None.
> Changes in V3:
> 	- Rebased on "[PATCH 0/2 V5] spi: Enable SPI_PREAMBLE Mode"
>   drivers/spi/exynos_spi.c |   19 +++++++++++++++++++
>   1 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c
> index 01378d0..03cf503 100644
> --- a/drivers/spi/exynos_spi.c
> +++ b/drivers/spi/exynos_spi.c
> @@ -38,6 +38,7 @@ struct spi_bus {
>   	struct exynos_spi *regs;
>   	int inited;		/* 1 if this bus is ready for use */
>   	int node;
> +	uint deactivate_delay_us;	/* Delay to wait after deactivate */
>   };
>
>   /* A list of spi buses that we know about */
> @@ -52,6 +53,8 @@ struct exynos_spi_slave {
>   	enum periph_id periph_id;	/* Peripheral ID for this device */
>   	unsigned int fifo_size;
>   	int skip_preamble;
> +	struct spi_bus *bus;		/* Pointer to our SPI bus info */
> +	ulong last_transaction_us;	/* Time of last transaction end */
>   };
>
>   static struct spi_bus *spi_get_bus(unsigned dev_index)
> @@ -97,6 +100,7 @@ struct spi_slave *spi_setup_slave(unsigned int busnum, unsigned int cs,
>   	}
>
>   	bus = &spi_bus[busnum];
> +	spi_slave->bus = bus;
>   	spi_slave->regs = bus->regs;
>   	spi_slave->mode = mode;
>   	spi_slave->periph_id = bus->periph_id;
> @@ -107,6 +111,7 @@ struct spi_slave *spi_setup_slave(unsigned int busnum, unsigned int cs,
>   		spi_slave->fifo_size = 256;
>
>   	spi_slave->skip_preamble = 0;
> +	spi_slave->last_transaction_us = timer_get_us();
>
>   	spi_slave->freq = bus->frequency;
>   	if (max_hz)
> @@ -371,9 +376,21 @@ void spi_cs_activate(struct spi_slave *slave)
>   {
>   	struct exynos_spi_slave *spi_slave = to_exynos_spi(slave);
>
> +	/* If it's too soon to do another transaction, wait */
> +	if (spi_slave->bus->deactivate_delay_us &&
> +	    spi_slave->last_transaction_us) {
> +		ulong delay_us;		/* The delay completed so far */
> +		delay_us = timer_get_us() - spi_slave->last_transaction_us;
> +		if (delay_us < spi_slave->bus->deactivate_delay_us)
> +			udelay(spi_slave->bus->deactivate_delay_us - delay_us);
> +	}
Add one space

>   	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;
> +
> +	/* Remember time of this transaction so we can honour the bus delay */
> +	if (spi_slave->bus->deactivate_delay_us)
> +		spi_slave->last_transaction_us = timer_get_us();
>   }
>
>   /**
> @@ -423,6 +440,8 @@ static int spi_get_config(const void *blob, int node, struct spi_bus *bus)
>   	/* Use 500KHz as a suitable default */
>   	bus->frequency = fdtdec_get_int(blob, node, "spi-max-frequency",
>   					500000);
> +	bus->deactivate_delay_us = fdtdec_get_int(blob, node,
> +					"spi-deactivate-delay", 0);
>
>   	return 0;
>   }
>

Was this tested, usually what is the max deactivate delay?
In this case your are passing through dts is it?

Thanks,
Jagan.