From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Price Subject: Re: [PATCH] drm/panfrost: Fix regulator_get_optional() misuse Date: Mon, 9 Sep 2019 17:22:55 +0100 Message-ID: <3e3a2c8a-b4fc-8af6-39e1-b26160db2c7c@arm.com> References: <20190904123032.23263-1-broonie@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: Tomeu Vizoso , David Airlie , "linux-kernel@vger.kernel.org" , dri-devel , Mark Brown List-Id: dri-devel@lists.freedesktop.org On 09/09/2019 16:41, Rob Herring wrote: > On Fri, Sep 6, 2019 at 4:23 PM Steven Price wrote: >> >> On 04/09/2019 13:30, Mark Brown wrote: >>> The panfrost driver requests a supply using regulator_get_optional() >>> but both the name of the supply and the usage pattern suggest that it is >>> being used for the main power for the device and is not at all optional >>> for the device for function, there is no meaningful handling for absent >>> supplies. Such regulators should use the vanilla regulator_get() >>> interface, it will ensure that even if a supply is not described in the >>> system integration one will be provided in software. >>> >>> Signed-off-by: Mark Brown >> >> Tested-by: Steven Price >> >> Looks like my approach to this was wrong - so we should also revert the >> changes I made previously. >> >> ----8<---- >> From fe20f8abcde8444bb41a8f72fb35de943a27ec5c Mon Sep 17 00:00:00 2001 >> From: Steven Price >> Date: Fri, 6 Sep 2019 15:20:53 +0100 >> Subject: [PATCH] drm/panfrost: Revert changes to cope with NULL regulator >> >> Handling a NULL return from devm_regulator_get_optional() doesn't seem >> like the correct way of handling this. Instead revert the changes in >> favour of switching to using devm_regulator_get() which will return a >> dummy regulator instead. >> >> Reverts commit 52282163dfa6 ("drm/panfrost: Add missing check for pfdev->regulator") >> Reverts commit e21dd290881b ("drm/panfrost: Enable devfreq to work without regulator") > > Does a straight revert of these 2 patches not work? If it does work, > can you do that and send to the list. I don't want my hand slapped > again reverting things. I wasn't sure what was best here - 52282163dfa6 is a bug fix, so reverting that followed by e21dd290881b would (re-)introduce a regression for that one commit (i.e. not completely bisectable). Reverting in the other order would work, but seems a little odd. Squashing the reverts seemed the neatest option - but it's not my hand at risk... :) Perhaps it would be best to simply apply Mark's change followed by something like the following. That way it's not actually a revert! It also avoids (re-)adding the now redundant check in panfrost_devfreq_init(). Steve ---8<---- >>From fb2956acdf46ca04095ef11363c136dc94a1ab18 Mon Sep 17 00:00:00 2001 From: Steven Price Date: Fri, 6 Sep 2019 15:20:53 +0100 Subject: [PATCH] drm/panfrost: Remove NULL checks for regulator devm_regulator_get() is now used to populate pfdev->regulator which ensures that this cannot be NULL (a dummy regulator will be returned if necessary). So remove the checks in panfrost_devfreq_target(). Signed-off-by: Steven Price --- drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c index a1f5fa6a742a..12ff77dacc95 100644 --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c @@ -39,7 +39,7 @@ static int panfrost_devfreq_target(struct device *dev, unsigned long *freq, * If frequency scaling from low to high, adjust voltage first. * If frequency scaling from high to low, adjust frequency first. */ - if (old_clk_rate < target_rate && pfdev->regulator) { + if (old_clk_rate < target_rate) { err = regulator_set_voltage(pfdev->regulator, target_volt, target_volt); if (err) { @@ -53,14 +53,12 @@ static int panfrost_devfreq_target(struct device *dev, unsigned long *freq, if (err) { dev_err(dev, "Cannot set frequency %lu (%d)\n", target_rate, err); - if (pfdev->regulator) - regulator_set_voltage(pfdev->regulator, - pfdev->devfreq.cur_volt, - pfdev->devfreq.cur_volt); + regulator_set_voltage(pfdev->regulator, pfdev->devfreq.cur_volt, + pfdev->devfreq.cur_volt); return err; } - if (old_clk_rate > target_rate && pfdev->regulator) { + if (old_clk_rate > target_rate) { err = regulator_set_voltage(pfdev->regulator, target_volt, target_volt); if (err) -- 2.20.1