linux-kernel - Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

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Message-ID: <000f26f4-3640-797f-c7f6-4b31a5e2669e@arm.com>
Date:   Tue, 14 Apr 2020 14:10:36 +0100
From:   Steven Price <steven.price@....com>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

Hi Clément,

On 13/04/2020 18:28, Clément Péron wrote:
> Hi Steven,
> 
> On Mon, 13 Apr 2020 at 18:35, Clément Péron <peron.clem@...il.com> wrote:
>>
>> Hi Steven,
>>
>> On Mon, 13 Apr 2020 at 17:55, Steven Price <steven.price@....com> wrote:
>>>
>>> On 13/04/2020 15:31, Clément Péron wrote:
>>>> Hi,
>>>>
>>>> On Mon, 13 Apr 2020 at 16:18, Clément Péron <peron.clem@...il.com> wrote:
>>>>>
>>>>> Hi Steven,
>>>>>
>>>>> On Mon, 13 Apr 2020 at 15:18, Steven Price <steven.price@....com> wrote:
>>>>>>
>>>>>> On 11/04/2020 21:06, Clément Péron wrote:
>>>>>>> OPP table can defined both frequency and voltage.
>>>>>>>
>>>>>>> Register the mali regulator if it exist.
>>>>>>>
>>>>>>> Signed-off-by: Clément Péron <peron.clem@...il.com>
>>>>>>> ---
>>>>>>>     drivers/gpu/drm/panfrost/panfrost_devfreq.c | 34 ++++++++++++++++++---
>>>>>>>     drivers/gpu/drm/panfrost/panfrost_device.h  |  1 +
>>>>>>>     2 files changed, 31 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>>>>>> index 62541f4edd81..2dc8e2355358 100644
>>>>>>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>>>>>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>>>>>> @@ -78,12 +78,26 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>>>>>>>         struct device *dev = &pfdev->pdev->dev;
>>>>>>>         struct devfreq *devfreq;
>>>>>>>         struct thermal_cooling_device *cooling;
>>>>>>> +     const char *mali = "mali";
>>>>>>> +     struct opp_table *opp_table = NULL;
>>>>>>> +
>>>>>>> +     /* Regulator is optional */
>>>>>>> +     opp_table = dev_pm_opp_set_regulators(dev, &mali, 1);
>>>>>>
>>>>>> This looks like it applies before 3e1399bccf51 ("drm/panfrost: Add
>>>>>> support for multiple regulators") which is currently in drm-misc-next
>>>>>> (and linux-next). You want something more like:
>>>>>
>>>>> Thanks for you review, indeed I didn't see that multiple regulators
>>>>> support has been added.
>>>>> Will update in v2.
>>>>>
>>>>>>
>>>>>>        opp_table = dev_pm_opp_set_regulators(dev,
>>>>>>                                              pfdev->comp->supply_names,
>>>>>>                                              pfdev->comp->num_supplies);
>>>>>>
>>>>>> Otherwise a platform with multiple regulators won't work correctly.
>>>>>>
>>>>>> Also running on my firefly (RK3288) board I get the following warning:
>>>>>>
>>>>>>       debugfs: Directory 'ffa30000.gpu-mali' with parent 'vdd_gpu' already
>>>>>> present!
> 
> I try to reproduce but it can't
> regulator is mount at :
> ./regulator/vdd-gpu
> whereas OPP is mount :
> ./opp/soc-1800000.gpu/opp:756000000/supply-0/

Getting a backtrace from the two occurrences, I see one added from:

   (debugfs_create_dir) from [<c04633f8>] (create_regulator+0xe0/0x220)
   (create_regulator) from [<c04681d8>] (_regulator_get+0x168/0x204)
   (_regulator_get) from [<c04682e0>] (regulator_bulk_get+0x64/0xf4)
   (regulator_bulk_get) from [<c04696f0>] 
(devm_regulator_bulk_get+0x40/0x74)
   (devm_regulator_bulk_get) from [<bf00af44>] 
(panfrost_device_init+0x1b4/0x48c [panfrost])
   (panfrost_device_init [panfrost]) from [<bf00a4d4>] 
(panfrost_probe+0x94/0x184 [panfrost])
   (panfrost_probe [panfrost]) from [<c04ee694>] 
(platform_drv_probe+0x48/0x94)

And the other:

   (debugfs_create_dir) from [<c04633f8>] (create_regulator+0xe0/0x220)
   (create_regulator) from [<c04681d8>] (_regulator_get+0x168/0x204)
   (_regulator_get) from [<c05c1280>] (dev_pm_opp_set_regulators+0x6c/0x184)
   (dev_pm_opp_set_regulators) from [<bf00b4ac>] 
(panfrost_devfreq_init+0x38/0x1ac [panfrost])
   (panfrost_devfreq_init [panfrost]) from [<bf00a508>] 
(panfrost_probe+0xc8/0x184 [panfrost])
   (panfrost_probe [panfrost]) from [<c04ee694>] 
(platform_drv_probe+0x48/0x94)

Both are created at /regulator/vdd_gpu

> 
> I see that firefly as 2 regulators with the same name :
> vdd_gpu from syr828
> (https://github.com/mopplayer/Firefly-RK3288-Kernel-With-Mali764/blob/master/arch/arm/boot/dts/firefly-rk3288.dts#L453)
> vdd_gpu from rk808_dcdc2_reg
> (https://github.com/mopplayer/Firefly-RK3288-Kernel-With-Mali764/blob/master/arch/arm/boot/dts/firefly-rk3288.dts#L841)
> 
> So i think the issue is from the firefly device-tree.

I'm using the DTB from the kernel tree 
(/arch/arm/boot/dts/rk3288-firefly.dts) which as far as I can see 
doesn't contain this problem. Certainly decompiling the DTB I can see 
only one mention of vdd_gpu (in syr828).

Steve

> 
> Regards,
> Clement
> 
>>>>>>
>>>>>> This is due to the regulator debugfs entries getting created twice (once
>>>>>> in panfrost_regulator_init() and once here).
>>>>>
>>>>> Is it a warning that should be consider as an error? Look's more an info no?
>>>>> What should be the correct behavior if a device want to register two
>>>>> times the same regulator?
>>>>
>>>> Or we can change the name from vdd_XXX to opp_vdd_XXX ?
>>>> https://elixir.bootlin.com/linux/latest/source/drivers/opp/debugfs.c#L45
>>>
>>> Yes, I'm not sure that it's actually a problem in practice. And it may
>>> well be correct to change this in the generic code rather than try to
>>> work around it in Panfrost. But we shouldn't spam the user with warnings
>>> as that makes real issues harder to see.
>>>
>>> Your suggestion to change the name seems reasonable to me, but I don't
>>> fully understand the opp code, so we'd need some review from the OPP
>>> maintainers. Hopefully Viresh, Nishanth or Stephen can provide some insight.
>>
>> Agree, I will send a v2 with the rename and see if OPP Maintainers agree.
>>
>> Regards,
>> Clement
>>
>>>
>>> Steve