Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx> 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 <cyrille.pitchen@xxxxxxxxx>
> ---
> drivers/spi/spi-atmel.c | 37 ++++++++++++++++++++++++++++---------
> 1 file changed, 28 insertions(+), 9 deletions(-)
[...]
> @@ -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.
--
Måns Rullgård
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
