From patchwork Wed Jun 22 08:04:22 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Boris BREZILLON X-Patchwork-Id: 9192145 X-Patchwork-Delegate: geert@linux-m68k.org Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A1E73601C0 for ; Wed, 22 Jun 2016 08:15:14 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 88E71283E6 for ; Wed, 22 Jun 2016 08:15:14 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7D349283ED; Wed, 22 Jun 2016 08:15:14 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B5EF2283E6 for ; Wed, 22 Jun 2016 08:15:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750721AbcFVIPM (ORCPT ); Wed, 22 Jun 2016 04:15:12 -0400 Received: from down.free-electrons.com ([37.187.137.238]:56633 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750770AbcFVIPE convert rfc822-to-8bit (ORCPT ); Wed, 22 Jun 2016 04:15:04 -0400 Received: by mail.free-electrons.com (Postfix, from userid 110) id A069425C; Wed, 22 Jun 2016 10:04:22 +0200 (CEST) Received: from bbrezillon (LStLambert-657-1-97-87.w90-63.abo.wanadoo.fr [90.63.216.87]) by mail.free-electrons.com (Postfix) with ESMTPSA id 3811B202; Wed, 22 Jun 2016 10:04:22 +0200 (CEST) Date: Wed, 22 Jun 2016 10:04:22 +0200 From: Boris Brezillon To: Brian Norris Cc: Geert Uytterhoeven , Thierry Reding , Linux PWM List , "linux-kernel@vger.kernel.org" , Brian Norris , Doug Anderson , linux-renesas-soc@vger.kernel.org, Laurent Pinchart Subject: Re: [PATCH v2] pwm: improve args checking in pwm_apply_state() Message-ID: <20160622100422.5c34f975@bbrezillon> In-Reply-To: <20160621183730.GA130978@google.com> References: <1464367549-111530-1-git-send-email-briannorris@chromium.org> <20160621183730.GA130978@google.com> Organization: Free Electrons X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Tue, 21 Jun 2016 11:37:31 -0700 Brian Norris wrote: > Hi Geert, > > On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote: > > On Fri, May 27, 2016 at 6:45 PM, Brian Norris wrote: > > > It seems like in the process of refactoring pwm_config() to utilize the > > > newly-introduced pwm_apply_state() API, some args/bounds checking was > > > dropped. > > > > > > In particular, I noted that we are now allowing invalid period > > > selections. e.g.: > > > > > > # echo 1 > /sys/class/pwm/pwmchip0/export > > > # cat /sys/class/pwm/pwmchip0/pwm1/period > > > 100 > > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle > > > [... driver may or may not reject the value, or trigger some logic bug ...] > > > > > > It's better to see: > > > > > > # echo 1 > /sys/class/pwm/pwmchip0/export > > > # cat /sys/class/pwm/pwmchip0/pwm1/period > > > 100 > > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle > > > -bash: echo: write error: Invalid argument > > > > > > This patch reintroduces some bounds checks in both pwm_config() (for its > > > signed parameters; we don't want to convert negative values into large > > > unsigned values) and in pwm_apply_state() (which fix the above described > > > behavior, as well as other potential API misuses). > > > > > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates") > > > Signed-off-by: Brian Norris > > > --- > > > v2: > > > * changed subject, as this covers more scope now > > > * add Fixes tag, as this is a v4.7-rc regression > > > * add more bounds/args checks in pwm_apply_state() and pwm_config() > > > > > > drivers/pwm/core.c | 3 ++- > > > include/linux/pwm.h | 3 +++ > > > 2 files changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > > > index dba3843c53b8..ed337a8c34ab 100644 > > > --- a/drivers/pwm/core.c > > > +++ b/drivers/pwm/core.c > > > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state) > > > { > > > int err; > > > > > > - if (!pwm) > > > + if (!pwm || !state || !state->period || > > > + state->duty_cycle > state->period) > > > return -EINVAL; > > > > This check breaks the LCD backlight on r8a7740/armadillo. > > Apparently both period and duty_cycle are zero during the first invocation. > > Later, these are initialized from DT, cfr. > > > > pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>; > > > > in arch/arm/boot/dts/r8a7740-armadillo800eva.dts. > > Hmm, this isn't super obvious how to best fix. On one hand, the > pwm_config() API used to reject period<=0, but on the other hand, I > think its replacement (pwm_apply_state()) is getting used in more places > than it used to be, and not all of them are really handling the "atomic > update" concept yet. Seems like a product of Boris's multi-phase attempt > to convert the PWM APIs to support atomic updates -- and many users > haven't really converted yet. > > > With added debug printing, the difference between failure and success is: > > > > renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered > > tpu_pwm_request:223 > > pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0 > > +Ignoring failure > > +pwm_apply_state:479: polarity 0 -> 1 > > +tpu_pwm_set_polarity:343 > > +pwm_apply_state:502: period 0 -> 0 > > +pwm_apply_state:503: duty_cycle 0 -> 0 > > +pwm_apply_state:516: enabled 0 -> 0 > > pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333 > > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333 > > -pwm_apply_state:479: polarity 0 -> 0 > > +pwm_apply_state:479: polarity 1 -> 1 > > pwm_apply_state:502: period 0 -> 33333 > > pwm_apply_state:503: duty_cycle 0 -> 33333 > > tpu_pwm_config:267 > > pwm_apply_state:516: enabled 0 -> 0 > > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333 > > -pwm_apply_state:479: polarity 0 -> 0 > > +pwm_apply_state:479: polarity 1 -> 1 > > pwm_apply_state:502: period 33333 -> 33333 > > pwm_apply_state:503: duty_cycle 33333 -> 33333 > > pwm_apply_state:516: enabled 0 -> 1 > > tpu_pwm_enable:354 > > I'm not sure I 100% understand this debug log, but I think maybe the > problem is in pwm_apply_args(), which calls pwm_disable() and > pwm_set_polarity() sequentially, without ever configuring a period? What > if pwm_apply_args() were to configure the period for us? > > Boris, any thoughts? > I had second thoughts and I think you're right: pwm_apply_args() should set the pargs.period period for us. Here is a patch addressing that. Geert, can you test it? --->8--- From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001 From: Boris Brezillon Date: Wed, 22 Jun 2016 09:25:14 +0200 Subject: [PATCH] pwm: Fix pwm_apply_args() Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates"), implemented pwm_disable() as a wrapper around pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args checking in pwm_apply_state()") added missing checks on the ->period value in pwm_apply_state() to ensure we were not passing inappropriate values to the ->config() or ->apply() methods. The conjunction of these 2 commits led to a case where pwm_disable() was no longer succeeding, thus preventing the polarity setting done in pwm_apply_args(). Set a valid period in pwm_apply_args() to ensure polarity setting won't be rejected. Signed-off-by: Boris Brezillon Reported-by: Geert Uytterhoeven Suggested-by: Brian Norris Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates") Tested-by: Geert Uytterhoeven Reviewed-by: Brian Norris --- include/linux/pwm.h | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 908b67c847cd..c038ae36b10e 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -464,6 +464,8 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm) static inline void pwm_apply_args(struct pwm_device *pwm) { + struct pwm_state state = { }; + /* * PWM users calling pwm_apply_args() expect to have a fresh config * where the polarity and period are set according to pwm_args info. @@ -476,18 +478,20 @@ static inline void pwm_apply_args(struct pwm_device *pwm) * at startup (even if they are actually enabled), thus authorizing * polarity setting. * - * Instead of setting ->enabled to false, we call pwm_disable() - * before pwm_set_polarity() to ensure that everything is configured - * as expected, and the PWM is really disabled when the user request - * it. + * To fulfill this requirement, we apply a new state which disables + * the PWM device and set the reference period and polarity config. * * Note that PWM users requiring a smooth handover between the * bootloader and the kernel (like critical regulators controlled by * PWM devices) will have to switch to the atomic API and avoid calling * pwm_apply_args(). */ - pwm_disable(pwm); - pwm_set_polarity(pwm, pwm->args.polarity); + + state.enabled = false; + state.polarity = pwm->args.polarity; + state.period = pwm->args.period; + + pwm_apply_state(pwm, &state); } struct pwm_lookup {