Re: [PATCH 6/7] drm: atmel-hlcdc: enable sys_clk during initalization.

[Claudiu.Beznea]

On 28.02.2019 23:55, Sam Ravnborg wrote:
> Hi Claudiu
> 
> On Wed, Feb 27, 2019 at 04:24:40PM +0000, Claudiu.Beznea@xxxxxxxxxxxxx wrote:
>> From: Sandeep Sheriker Mallikarjun <sandeepsheriker.mallikarjun@xxxxxxxxxxxxx>
>>
>> For SAM9X60 SoC, sys_clk is through lcd_gclk clock source and this
>> needs to be enabled before enabling lcd_clk.
> 
> We have "ownership" of the clocks in the mfd device.
> So it would make more sense to let the mfd device handle
> the base clocks.
> In other words - what about pushing enable of perigh_clk and sys_clk to
> the mfd driver.

I think this could be achieved, but how is better? To have individual
drivers (in this care I would say, child drivers, like e.g. this lcd
driver) taking decisions on their own for their resources (even if shared)
or to have parents taking decisions for them? Just asking.

> 
> This may have the nice side-effect that we avoid
> that both the drm driver and the pwm driver enable/disable the periph_clk
> as it is today.
> 
> Another comment - fixed_clksrc is used to determine if sys_clk is enabled.
> But that flag is about the clksource selection, and it is just a coincidence
> that the same flag can be used here.

Yes, agree on this, I took advantage of fixed_clksrc to also enable the
sys_clk based on fixed_clksrc to avoid introducing another member in struct
atmel_hlcdc_dc_desc. At this moment this is valid only for SAM9X60 and I
was thinking that in case some other scenario will appear I will do the
appropriate changes.

> Why we cannot always enable sys_clk? Do we need to do this only
> for sam9x60?

Only SAM9X60 requires this explicitly at probe.

> IF yes, then add a new falg. If no, then skip the flag.
> 
> 	Sam
> 
> 
>>
>> Signed-off-by: Sandeep Sheriker Mallikarjun <sandeepsheriker.mallikarjun@xxxxxxxxxxxxx>
>> [claudiu.beznea@xxxxxxxxxxxxx: add fixed_clksrc checks]
>> Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c | 19 ++++++++++++++++++-
>>  1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c
>> index 0be13eceedba..8bf51f853721 100644
>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c
>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c
>> @@ -625,10 +625,18 @@ static int atmel_hlcdc_dc_load(struct drm_device *dev)
>>  	dc->hlcdc = dev_get_drvdata(dev->dev->parent);
>>  	dev->dev_private = dc;
>>  
>> +	if (dc->desc->fixed_clksrc) {
>> +		ret = clk_prepare_enable(dc->hlcdc->sys_clk);
>> +		if (ret) {
>> +			dev_err(dev->dev, "failed to enable sys_clk\n");
>> +			goto err_destroy_wq;
>> +		}
>> +	}
>> +
>>  	ret = clk_prepare_enable(dc->hlcdc->periph_clk);
>>  	if (ret) {
>>  		dev_err(dev->dev, "failed to enable periph_clk\n");
>> -		goto err_destroy_wq;
>> +		goto err_sys_clk_disable;
>>  	}
>>  
>>  	pm_runtime_enable(dev->dev);
>> @@ -664,6 +672,9 @@ static int atmel_hlcdc_dc_load(struct drm_device *dev)
>>  err_periph_clk_disable:
>>  	pm_runtime_disable(dev->dev);
>>  	clk_disable_unprepare(dc->hlcdc->periph_clk);
>> +err_sys_clk_disable:
>> +	if (dc->desc->fixed_clksrc)
>> +		clk_disable_unprepare(dc->hlcdc->sys_clk);
>>  
>>  err_destroy_wq:
>>  	destroy_workqueue(dc->wq);
>> @@ -688,6 +699,8 @@ static void atmel_hlcdc_dc_unload(struct drm_device *dev)
>>  
>>  	pm_runtime_disable(dev->dev);
>>  	clk_disable_unprepare(dc->hlcdc->periph_clk);
>> +	if (dc->desc->fixed_clksrc)
>> +		clk_disable_unprepare(dc->hlcdc->sys_clk);
>>  	destroy_workqueue(dc->wq);
>>  }
>>  
>> @@ -805,6 +818,8 @@ static int atmel_hlcdc_dc_drm_suspend(struct device *dev)
>>  	regmap_read(regmap, ATMEL_HLCDC_IMR, &dc->suspend.imr);
>>  	regmap_write(regmap, ATMEL_HLCDC_IDR, dc->suspend.imr);
>>  	clk_disable_unprepare(dc->hlcdc->periph_clk);
>> +	if (dc->desc->fixed_clksrc)
>> +		clk_disable_unprepare(dc->hlcdc->sys_clk);
>>  
>>  	return 0;
>>  }
>> @@ -814,6 +829,8 @@ static int atmel_hlcdc_dc_drm_resume(struct device *dev)
>>  	struct drm_device *drm_dev = dev_get_drvdata(dev);
>>  	struct atmel_hlcdc_dc *dc = drm_dev->dev_private;
>>  
>> +	if (dc->desc->fixed_clksrc)
>> +		clk_prepare_enable(dc->hlcdc->sys_clk);
>>  	clk_prepare_enable(dc->hlcdc->periph_clk);
>>  	regmap_write(dc->hlcdc->regmap, ATMEL_HLCDC_IER, dc->suspend.imr);
>>  
>> -- 
>> 2.7.4
>>
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