From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: Re: [PATCH REGRESSION-FIX resend] pwm: lpss: Set enable-bit before waiting for update-bit Date: Tue, 28 Mar 2017 19:20:11 +0200 Message-ID: References: <20170325140658.26868-1-hdegoede@redhat.com> <1490712327.708.30.camel@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:23795 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754410AbdC1RUU (ORCPT ); Tue, 28 Mar 2017 13:20:20 -0400 In-Reply-To: <1490712327.708.30.camel@linux.intel.com> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Andy Shevchenko , Thierry Reding Cc: linux-pwm@vger.kernel.org, "Koskinen, Ilkka" Hi, On 03/28/2017 04:45 PM, Andy Shevchenko wrote: > On Sat, 2017-03-25 at 15:06 +0100, Hans de Goede wrote: >> Hi Andy, Thierry, >> >> This patch fixes a regression with the pwm-lpss driver in 4.11, >> where it once turned off will not turn back on again on some >> machines. Yet it has been silent around this patch for some >> time now. Can you please review this and get it queued as a fix >> for 4.11 ? > > I have tested this patch (*) on 3 boards: > 1) internal development board (ApolloLake) > 2) MinnowBoard MAX (BayTrail) > 3) Intel Edison / Arduino break out (Tangier) > 4) ...not yet... (CherryTrail / Braswell) > > So, the patch *broke* functionality on 1), while 2) and 3) are survived. Bummer, so on Apollo Lake we need to set the update bit *and* wait for it to get acked before setting enable ? NOte my patch does not change the order of writes, only when we do the wait. The only good options I see to fix this is to introduce SoC family specific code paths :| If you can whip up a new version which is tested on Apollo Lake and Bay Trail I can run some tests on Cherry Trail. Regards, Hans > > (*) The base is my eds branch (https://github.com/andy-shev/linux/tree/e > ds, v4.11-rc4 based) + few pin control related patches to enable PWM > output. > > P.S. I'll continue looking for CherryTrail / Braswell based board to > have some coverage there in the future. >