[PATCH v3 1/3] spi: atmel: add support for the internal chip-select of the spi controller
flat view
From: Måns Rullgård <hidden>
Date: 2016-01-05 21:50:59
Also in:
linux-devicetree, linux-spi, lkml
Cyrille Pitchen [off-list ref] writes:
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 <redacted> --- drivers/spi/spi-atmel.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-)
[...]
quoted hunk
@@ -1338,6 +1350,13 @@ static int atmel_spi_probe(struct platform_device *pdev) 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; + }
This part breaks the AVR32 boards and probably anything else that doesn't use devicetree but does use GPIOs for chip select. -- M?ns Rullg?rd