[Lima] [PATCH] drm/lima: Convert to clk_bulk API

[Marek Vasut]

On 7/17/21 4:21 PM, Qiang Yu wrote:
> On Sat, Jul 17, 2021 at 9:08 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 7/17/21 2:34 PM, Qiang Yu wrote:
>>> On Sat, Jul 17, 2021 at 2:20 AM Marek Vasut <marex at denx.de> wrote:
>>>>
>>>> Instead of requesting two separate clock and then handling them
>>>> separately in various places of the driver, use clk_bulk_*() API.
>>>> This permits handling devices with more than "bus"/"core" clock,
>>>> like ZynqMP, which has "gpu"/"gpu_pp0"/"gpu_pp1" all as separate
>>>> clock.
>>>
>>> I can't find the ZynqMP DTS file under arch/arm64/boot/dts/xilinx
>>> which has mali GPU node with an upstream kernel, where is it?
>>
>> Posted here:
>> https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210716182544.219490-1-marex@denx.de/
>>
>>> So what's the relationship between "gpu" clk and "gpu_pp0"/"gpu_pp1"
>>> clk? Do they need to be controlled separately or we can just control the
>>> "gpu" clk? Because the devfreq code just controls a single module clk.
>>
>> Per the docs, they are separate enable bits and the zynqmp clock
>> controller exports them as separate clock, see bits 24..26 here:
>>
>> https://www.xilinx.com/html_docs/registers/ug1087/crf_apb___gpu_ref_ctrl.html
>>
>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>> Cc: Qiang Yu <yuq825 at gmail.com>
>>>> Cc: lima at lists.freedesktop.org
>>>> ---
>>>>    drivers/gpu/drm/lima/lima_devfreq.c | 17 +++++++++---
>>>>    drivers/gpu/drm/lima/lima_devfreq.h |  1 +
>>>>    drivers/gpu/drm/lima/lima_device.c  | 42 +++++++++++------------------
>>>>    drivers/gpu/drm/lima/lima_device.h  |  4 +--
>>>>    4 files changed, 32 insertions(+), 32 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/lima/lima_devfreq.c b/drivers/gpu/drm/lima/lima_devfreq.c
>>>> index 8989e215dfc9..533b36932f79 100644
>>>> --- a/drivers/gpu/drm/lima/lima_devfreq.c
>>>> +++ b/drivers/gpu/drm/lima/lima_devfreq.c
>>>> @@ -58,7 +58,7 @@ static int lima_devfreq_get_dev_status(struct device *dev,
>>>>           struct lima_devfreq *devfreq = &ldev->devfreq;
>>>>           unsigned long irqflags;
>>>>
>>>> -       status->current_frequency = clk_get_rate(ldev->clk_gpu);
>>>> +       status->current_frequency = clk_get_rate(devfreq->clk_gpu);
>>>>
>>>>           spin_lock_irqsave(&devfreq->lock, irqflags);
>>>>
>>>> @@ -110,12 +110,23 @@ int lima_devfreq_init(struct lima_device *ldev)
>>>>           struct lima_devfreq *ldevfreq = &ldev->devfreq;
>>>>           struct dev_pm_opp *opp;
>>>>           unsigned long cur_freq;
>>>> -       int ret;
>>>> +       int i, ret;
>>>>
>>>>           if (!device_property_present(dev, "operating-points-v2"))
>>>>                   /* Optional, continue without devfreq */
>>>>                   return 0;
>>>>
>>>> +       /* Find first clock which are not "bus" clock */
>>>> +       for (i = 0; i < ldev->nr_clks; i++) {
>>>> +               if (!strcmp(ldev->clks[i].id, "bus"))
>>>> +                       continue;
>>>> +               ldevfreq->clk_gpu = ldev->clks[i].clk;
>>>> +               break;
>>>> +       }
>>>
>>> I'd prefer an explicit name for the required clk name. If some DTS has different
>>> name other than "core" for the module clk (ie. "gpu"), it should be changed to
>>> "core".
>>
>> The problem here is, the zynqmp has no core clock, it has "gpu and both
>> pixel pipes" super-clock-gate which controls everything, and then
>> per-pixel-pipe sub-clock-gates.
> 
> So the "gpu" clk can gate both "gpu_pp0" and "gpu_pp1" clk, how about frequency?

I don't think it is a good idea to just gate off the root clock while 
the sub-clock are still enabled. That might lead to latch ups (+CC 
Michal, he might know more).

And who would enable the sub-clock anyway, it should be the GPU driver, no?

> Can we set clock rate for "gpu" then "gpu_pp0" and "gpu_pp1" pass
> through the same
> rate? If so, "gpu" works just like "core".

I don't think the zynqmp is capable of any DVFS on the GPU at all, it 
just runs at fixed frequency.