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spi: exynos: Support a delay after deactivate

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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.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rajeshwari S Shinde <rajeshwari.s@samsung.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
This commit is contained in:
Rajeshwari Shinde 2013-10-08 16:20:04 +05:30 committed by Jagannadha Sutradharudu Teki
parent fc9ae1bac4
commit 8d203afdd3
1 changed files with 20 additions and 0 deletions
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20
drivers/spi/exynos_spi.c
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@ -26,6 +26,7 @@ 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 */
@ -40,6 +41,8 @@ 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)
@ -85,6 +88,7 @@ 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;
@ -95,6 +99,7 @@ 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)
@ -359,9 +364,22 @@ 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);
}
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();
}
/**
@ -411,6 +429,8 @@ 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;
}