Re: [PATCH v6 2/6] drm/etnaviv: add a dedicated function to get various clocks

[Sui Jingfeng]

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@xxxxxxxxxxx>
> > ---
> >   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