From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757407AbaIXCwF (ORCPT ); Tue, 23 Sep 2014 22:52:05 -0400 Received: from va-smtp01.263.net ([54.88.144.211]:56343 "EHLO va-smtp01.263.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755179AbaIXCwD (ORCPT ); Tue, 23 Sep 2014 22:52:03 -0400 X-RL-SENDER: zyw@rock-chips.com X-FST-TO: dianders@chromium.org X-SENDER-IP: 127.0.0.1 X-LOGIN-NAME: zyw@rock-chips.com X-UNIQUE-TAG: X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 1 Message-ID: <542231C9.1060903@rock-chips.com> Date: Wed, 24 Sep 2014 10:51:53 +0800 From: Chris Zhong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Doug Anderson CC: =?UTF-8?B?SGVpa28gU3TDvGJuZXI=?= , linux-rockchip@lists.infradead.org, Lee Jones , "broonie@kernel.org" , Liam Girdwood , Grant Likely , Rob Herring , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" Subject: Re: [PATCH v6 1/2] regulator: st-pwm: get voltage and duty table from dts References: <1411487622-10881-1-git-send-email-zyw@rock-chips.com> <1411487622-10881-2-git-send-email-zyw@rock-chips.com> <542222BC.4060203@rock-chips.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2014 10:13 AM, Doug Anderson wrote: > Chris, > > On Tue, Sep 23, 2014 at 6:47 PM, Chris Zhong wrote: >> On 09/24/2014 07:43 AM, Doug Anderson wrote: >>> Chris, >>> >>> On Tue, Sep 23, 2014 at 8:53 AM, Chris Zhong wrote: >>>> Get voltage & duty table from device tree might be better, other >>>> platforms can also use this >>>> driver without any modify. >>>> >>>> Signed-off-by: Chris Zhong >>>> Reviewed-by: Doug Anderson >>> I finally managed to get everything setup and I've now tested this >>> myself on an rk3288-based board. >>> >>> Tested-by: Doug Anderson >>> >>> I'd imagine the next step is for Lee to comment on the patch and when >>> he's happy with it Mark Brown will land it? >>> >>> >>> One thing that's still a bit odd (though no different than the >>> behavior of the driver from before you touched it, so it shouldn't >>> block landing IMHO) is that at boot time this regulator will report >>> that it's at the highest voltage but the voltage won't actually change >>> until the first client sets the voltage. >> Yes, I knew this problem, since the default of duty cycle is 0, not a true >> value. >> If we can get duty from pwm, this regulator will report a correct voltage. > I don't think it's possible in all cases to figure out what the > voltage was before this regulator was probed. > > * pin might have been input w/ pullup, pulldown, or no pull > * pin might have been driven high or driven low > > In that case trying to read the duty from the pwm wouldn't make sense. > ...but I guess you could add a property to the PWM driver to say that > it stays enabled at boot if the FW left it enabled (and keep the same > duty cycle / clocks?). That would at least solve the problem where > the firmware configured the PWM and left it in a specific state even > if it doesn't solve the above problem... > > > -Doug > If we want pwm stay enabled at boot(FW left it), needn't to modify anything, only need to init pwm duty in FW. And now reading the duty from pwm would make sense.