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SubjectRe: [PATCH 2/2] drm/panfrost: add devfreq regulator support
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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@gmail.com> wrote:
>>
>> Hi Steven,
>>
>> On Mon, 13 Apr 2020 at 17:55, Steven Price <steven.price@arm.com> wrote:
>>>
>>> On 13/04/2020 15:31, Clément Péron wrote:
>>>> Hi,
>>>>
>>>> On Mon, 13 Apr 2020 at 16:18, Clément Péron <peron.clem@gmail.com> wrote:
>>>>>
>>>>> Hi Steven,
>>>>>
>>>>> On Mon, 13 Apr 2020 at 15:18, Steven Price <steven.price@arm.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@gmail.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

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