According to the datasheet we need to wait 100us before accessing any registers in the KS8995 after a reset de-assertion. Add this delay, if and only if we obtained a GPIO descriptor, otherwise it is just a pointless delay. Signed-off-by: Linus Walleij --- drivers/net/dsa/ks8995.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/net/dsa/ks8995.c b/drivers/net/dsa/ks8995.c index d135b061d810b7ba0c0731d43d176f3ba46b3f52..bdee8c62315f336e380313558c66127ff0b701d3 100644 --- a/drivers/net/dsa/ks8995.c +++ b/drivers/net/dsa/ks8995.c @@ -438,9 +438,15 @@ static int ks8995_probe(struct spi_device *spi) if (err) return err; - /* de-assert switch reset */ - /* FIXME: this likely requires a delay */ - gpiod_set_value_cansleep(ks->reset_gpio, 0); + if (ks->reset_gpio) { + /* + * If a reset line was obtained, wait for 100us after + * de-asserting RESET before accessing any registers, see + * the KS8995MA datasheet, page 44. + */ + gpiod_set_value_cansleep(ks->reset_gpio, 0); + udelay(100); + } spi_set_drvdata(spi, ks); -- 2.50.1