spi: atmel: add support for the internal chip-select of the spi controller
This patch relies on the CSAAT (Chip Select Active After Transfer) feature
introduced by the version 2 of the spi controller. This new mode allows to
use properly the internal chip-select output pin of the spi controller
instead of using external gpios. Consequently, the "cs-gpios" device-tree
property becomes optional.
When the new CSAAT bit is set into the Chip Select Register, the internal
chip-select output pin remains asserted till both the following conditions
become true:
- the LASTXFER bit is set into the Control Register (or the Transmit Data
Register)
- the Transmit Data Register and its shift register are empty.
WARNING: if the LASTXFER bit is set into the Control Register then new
data are written into the Transmit Data Register fast enough to keep its
shifter not empty, the chip-select output pin remains asserted. Only when
the shifter becomes empty, the chip-select output pin is unasserted.
When the CSAAT bit is clear in the Chip Select Register, the LASTXFER bit
is ignored in both the Control Register and the Transmit Data Register.
The internal chip-select output pin remains active as long as the Transmit
Data Register or its shift register are not empty.
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index a2f40b1..aa7d202 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -246,6 +246,7 @@
bool use_dma;
bool use_pdc;
+ bool use_cs_gpios;
/* dmaengine data */
struct atmel_spi_dma dma;
@@ -321,7 +322,8 @@
}
mr = spi_readl(as, MR);
- gpio_set_value(asd->npcs_pin, active);
+ if (as->use_cs_gpios)
+ gpio_set_value(asd->npcs_pin, active);
} else {
u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0;
int i;
@@ -337,7 +339,7 @@
mr = spi_readl(as, MR);
mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);
- if (spi->chip_select != 0)
+ if (as->use_cs_gpios && spi->chip_select != 0)
gpio_set_value(asd->npcs_pin, active);
spi_writel(as, MR, mr);
}
@@ -366,7 +368,9 @@
asd->npcs_pin, active ? " (low)" : "",
mr);
- if (atmel_spi_is_v2(as) || spi->chip_select != 0)
+ if (!as->use_cs_gpios)
+ spi_writel(as, CR, SPI_BIT(LASTXFER));
+ else if (atmel_spi_is_v2(as) || spi->chip_select != 0)
gpio_set_value(asd->npcs_pin, !active);
}
@@ -996,6 +1000,8 @@
csr |= SPI_BIT(CPOL);
if (!(spi->mode & SPI_CPHA))
csr |= SPI_BIT(NCPHA);
+ if (!as->use_cs_gpios)
+ csr |= SPI_BIT(CSAAT);
/* DLYBS is mostly irrelevant since we manage chipselect using GPIOs.
*
@@ -1009,7 +1015,9 @@
/* chipselect must have been muxed as GPIO (e.g. in board setup) */
npcs_pin = (unsigned long)spi->controller_data;
- if (gpio_is_valid(spi->cs_gpio))
+ if (!as->use_cs_gpios)
+ npcs_pin = spi->chip_select;
+ else if (gpio_is_valid(spi->cs_gpio))
npcs_pin = spi->cs_gpio;
asd = spi->controller_state;
@@ -1018,15 +1026,19 @@
if (!asd)
return -ENOMEM;
- ret = gpio_request(npcs_pin, dev_name(&spi->dev));
- if (ret) {
- kfree(asd);
- return ret;
+ if (as->use_cs_gpios) {
+ ret = gpio_request(npcs_pin, dev_name(&spi->dev));
+ if (ret) {
+ kfree(asd);
+ return ret;
+ }
+
+ gpio_direction_output(npcs_pin,
+ !(spi->mode & SPI_CS_HIGH));
}
asd->npcs_pin = npcs_pin;
spi->controller_state = asd;
- gpio_direction_output(npcs_pin, !(spi->mode & SPI_CS_HIGH));
}
asd->csr = csr;
@@ -1338,6 +1350,13 @@
atmel_get_caps(as);
+ as->use_cs_gpios = true;
+ if (atmel_spi_is_v2(as) &&
+ !of_get_property(pdev->dev.of_node, "cs-gpios", NULL)) {
+ as->use_cs_gpios = false;
+ master->num_chipselect = 4;
+ }
+
as->use_dma = false;
as->use_pdc = false;
if (as->caps.has_dma_support) {