Hi Jonathan, On Mon, Aug 15, 2016 at 07:04:31PM +0100, Jonathan Cameron wrote: > On 26/07/16 04:22, Guenter Roeck wrote: > > On 07/25/2016 07:51 PM, Caesar Wang wrote: > >> Hi Guenter, > >> > >> Thanks for fixing it. > >> > >> On 2016年07月26日 03:39, Guenter Roeck wrote: > >>> If the ADC is read for the first time, the caller gets a timeout error, > >>> and the kernel log shows > >>> > >>> read channel() error: -110 > >>> > >>> The ADC may be enabled on boot, and needs to be explicitly disabled > >>> for a read sequence to work (otherwise there is no completion interrupt). > >>> Disaple it explicitly in the probe function. > >>> > >>> Fixes: 44d6f2ef94f9 ("iio: adc: add driver for Rockchip saradc") > >>> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx> > >>> --- > >>> drivers/iio/adc/rockchip_saradc.c | 3 +++ > >>> 1 file changed, 3 insertions(+) > >>> > >>> diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c > >>> index f9ad6c2d6821..6aa3271d86b5 100644 > >>> --- a/drivers/iio/adc/rockchip_saradc.c > >>> +++ b/drivers/iio/adc/rockchip_saradc.c > >>> @@ -280,6 +280,9 @@ static int rockchip_saradc_probe(struct platform_device *pdev) > >>> goto err_pclk; > >>> } > >>> + /* Make sure ADC is disabled */ > >>> + writel_relaxed(0, info->regs + SARADC_CTRL); > >> > >> I think we should reset the saradc controller. > >> Since make sure the reset value is 0 and loader-->kernel may even cause harm, as my experience on tsadc. (drivers/thermal/rockchip_thermal.c) > >> > >> > >> e.g.: > >> /** > >> * Reset SARADC Controller, reset all saradc registers. > >> */ > >> static void rockchip_saradc_reset_controller(struct reset_control *reset) > >> { > >> reset_control_assert(reset); > >> usleep_range(10, 20); > >> reset_control_deassert(reset); > >> } > >> > >> ..probe() > >> { > >> ... > >> rockchip_saradc_reset_controller(); > >> ... > >> } > >> > > > > Ok, I'll give it a try. > > > > Guenter > Could you confirm if this patch is superseded by that > change or not? Yes, that is correct. The version using the reset has been applied to chromeos-4.4 [1] with commit 86aeb7c3f ("FROMLIST: iio: adc: rockchip_saradc: reset saradc controller before programming it"). Thanks, Guenter --- [1] https://chromium.googlesource.com/chromiumos/third_party/kernel -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html