From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Ni Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control Date: Tue, 10 Sep 2013 19:29:40 +0800 Message-ID: <522F02A4.7060702@nvidia.com> References: <20130909111242.GW29403@sirena.org.uk> <522DB253.6000707@roeck-us.net> <20130909135022.GZ29403@sirena.org.uk> <20130909155043.GA18975@roeck-us.net> <20130909160237.GR29403@sirena.org.uk> <20130909161735.GC18975@roeck-us.net> <20130909203910.GV29403@sirena.org.uk> <522E9A85.9050803@nvidia.com> <522EA51C.90706@roeck-us.net> <522EB0AF.9030708@nvidia.com> <20130910101359.GX29403@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130910101359.GX29403@sirena.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Mark Brown Cc: Guenter Roeck , "khali@linux-fr.org" , "swarren@wwwdotorg.org" , "lm-sensors@lm-sensors.org" , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: linux-tegra@vger.kernel.org On 09/10/2013 06:13 PM, Mark Brown wrote: > * PGP Signed by an unknown key > > On Tue, Sep 10, 2013 at 01:39:59PM +0800, Wei Ni wrote: > >> I think the device need time to wait stable after power on, but it's >> difficult to get an exact delay value, and this delay may also relate >> with platform design, so how about to add a optional property in the DT >> node, such as "power-on-delay-ms" ? > > This is something you should *really* be able to get from the datasheet > for the part - this sort of stuff has to be documented for hardware to > be used robustly. It seems entirely possible that you are working > around an issue with the regulator driver you are using not correctly > providing its ramp time here. On my platform, it use palmas-regulator.c, ldo6 for this lm90 power rail. I checked this driver, it will handle ramp_delay except LDOx. Since I'm not familiar with this palmas device and driver, so do you mean I can set regulator-ramp-delay property in the DT for ldo6, but I really don't know what value should I set :( Thanks. Wei. > > * Unknown Key > * 0x7EA229BD >