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SubjectRe: [PATCH v6 2/6] drm/etnaviv: add a dedicated function to get various clocks
From
Hi,

On 2023/6/1 02:07, Lucas Stach wrote:
> Am Mittwoch, dem 31.05.2023 um 00:06 +0800 schrieb Sui Jingfeng:
>> Because it is also platform-dependent, there are environments where don't
>> have CLK subsystem support, for example, discreted PCI gpu. So don't rage
>> quit if there is no CLK subsystem.
>>
>> For the GPU in LS7a1000 and LS2k2000, the working frequency of the GPU is
>> tuned by configuring the PLL register directly.
>>
> Is this PLL under control of system firmware and invisible to Linux?
Yes, it is registers, both system firmware and kernel space driver can
access it.
>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
>> ---
>> drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 62 ++++++++++++++++++---------
>> drivers/gpu/drm/etnaviv/etnaviv_gpu.h | 1 +
>> 2 files changed, 42 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
>> index 636d3f39ddcb..4937580551a5 100644
>> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
>> @@ -1565,10 +1565,45 @@ static irqreturn_t irq_handler(int irq, void *data)
>> return ret;
>> }
>>
>> +static int etnaviv_gpu_clk_get(struct etnaviv_gpu *gpu)
>> +{
>> + struct device *dev = gpu->dev;
>> +
>> + if (gpu->no_clk)
>> + return 0;
>> +
>> + gpu->clk_reg = devm_clk_get_optional(dev, "reg");
>> + DBG("clk_reg: %p", gpu->clk_reg);
>> + if (IS_ERR(gpu->clk_reg))
>> + return PTR_ERR(gpu->clk_reg);
>> +
>> + gpu->clk_bus = devm_clk_get_optional(dev, "bus");
>> + DBG("clk_bus: %p", gpu->clk_bus);
>> + if (IS_ERR(gpu->clk_bus))
>> + return PTR_ERR(gpu->clk_bus);
>> +
>> + gpu->clk_core = devm_clk_get(dev, "core");
>> + DBG("clk_core: %p", gpu->clk_core);
>> + if (IS_ERR(gpu->clk_core))
>> + return PTR_ERR(gpu->clk_core);
>> + gpu->base_rate_core = clk_get_rate(gpu->clk_core);
>> +
>> + gpu->clk_shader = devm_clk_get_optional(dev, "shader");
>> + DBG("clk_shader: %p", gpu->clk_shader);
>> + if (IS_ERR(gpu->clk_shader))
>> + return PTR_ERR(gpu->clk_shader);
>> + gpu->base_rate_shader = clk_get_rate(gpu->clk_shader);
>> +
>> + return 0;
>> +}
>> +
>> static int etnaviv_gpu_clk_enable(struct etnaviv_gpu *gpu)
>> {
>> int ret;
>>
>> + if (gpu->no_clk)
>> + return 0;
>> +
> I don't see why this would be needed? If your platform doesn't provide
> CONFIG_HAVE_CLK all those functions should be successful no-ops, so
> there is no need to special case this in the driver.
>
> Or does your platform in fact provide a clk subsystem, just the GPU
> clocks are managed by it?
>
> Also all those functions are fine with being called on a NULL clk,
right
> so
> shouldn't it be enough to simply avoid calling etnaviv_gpu_clk_get() in
> the PCI device case?

Yes, I just tried, your are right.

There also no need to add the 'no_clk' member into struct etnaviv_gpu

> Regards,
> Lucas
>
>> ret = clk_prepare_enable(gpu->clk_reg);
>> if (ret)
>> return ret;
>> @@ -1599,6 +1634,9 @@ static int etnaviv_gpu_clk_enable(struct etnaviv_gpu *gpu)
>>
>> static int etnaviv_gpu_clk_disable(struct etnaviv_gpu *gpu)
>> {
>> + if (gpu->no_clk)
>> + return 0;
>> +
>> clk_disable_unprepare(gpu->clk_shader);
>> clk_disable_unprepare(gpu->clk_core);
>> clk_disable_unprepare(gpu->clk_bus);
>> @@ -1865,27 +1903,9 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
>> return err;
>>
>> /* Get Clocks: */
>> - gpu->clk_reg = devm_clk_get_optional(&pdev->dev, "reg");
>> - DBG("clk_reg: %p", gpu->clk_reg);
>> - if (IS_ERR(gpu->clk_reg))
>> - return PTR_ERR(gpu->clk_reg);
>> -
>> - gpu->clk_bus = devm_clk_get_optional(&pdev->dev, "bus");
>> - DBG("clk_bus: %p", gpu->clk_bus);
>> - if (IS_ERR(gpu->clk_bus))
>> - return PTR_ERR(gpu->clk_bus);
>> -
>> - gpu->clk_core = devm_clk_get(&pdev->dev, "core");
>> - DBG("clk_core: %p", gpu->clk_core);
>> - if (IS_ERR(gpu->clk_core))
>> - return PTR_ERR(gpu->clk_core);
>> - gpu->base_rate_core = clk_get_rate(gpu->clk_core);
>> -
>> - gpu->clk_shader = devm_clk_get_optional(&pdev->dev, "shader");
>> - DBG("clk_shader: %p", gpu->clk_shader);
>> - if (IS_ERR(gpu->clk_shader))
>> - return PTR_ERR(gpu->clk_shader);
>> - gpu->base_rate_shader = clk_get_rate(gpu->clk_shader);
>> + err = etnaviv_gpu_clk_get(gpu);
>> + if (err)
>> + return err;
>>
>> /* TODO: figure out max mapped size */
>> dev_set_drvdata(dev, gpu);
>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
>> index 98c6f9c320fc..6da5209a7d64 100644
>> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
>> @@ -148,6 +148,7 @@ struct etnaviv_gpu {
>> struct clk *clk_reg;
>> struct clk *clk_core;
>> struct clk *clk_shader;
>> + bool no_clk;
>>
>> unsigned int freq_scale;
>> unsigned long base_rate_core;

--
Jingfeng

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