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 --- drivers/spi/exynos_spi.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c index efc8b1e..d7fdaac 100644 --- a/drivers/spi/exynos_spi.c +++ b/drivers/spi/exynos_spi.c @@ -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; }