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"
Signed-off-by: Simon Glass <s...@chromium.org>
Signed-off-by: Rajeshwari Shinde <rajeshwar...@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);
+ }
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;
}
--
1.7.4.4
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