spi: exynos: Support a delay after deactivate
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>
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 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 @@
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 @@
}
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 @@
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 @@
{
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 @@
/* 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;
}