From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] iio: adc: rockchip_saradc: Explicitly disable ADC on probe Date: Mon, 15 Aug 2016 12:52:29 -0700 Message-ID: <20160815195229.GB4400@roeck-us.net> References: <1469475540-26855-1-git-send-email-linux@roeck-us.net> <5796D036.1060101@rock-chips.com> <5796D792.4080407@roeck-us.net> <8ebf4c53-21e2-0220-1756-beb57af32304@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <8ebf4c53-21e2-0220-1756-beb57af32304-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jonathan Cameron Cc: Caesar Wang , Heiko Stuebner , linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-rockchip.vger.kernel.org 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 > >>> --- > >>> 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