linux-kernel - Re: [PATCH] drm/stm: ltdc: remove clk_round

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Message-ID: <65e9219b-3f64-01bb-645c-d3746e2363e7@st.com>
Date:   Mon, 13 May 2019 13:12:56 +0000
From:   Yannick FERTRE <yannick.fertre@...com>
To:     Philippe CORNU <philippe.cornu@...com>,
        Benjamin GAIGNARD <benjamin.gaignard@...com>,
        Vincent ABRIOU <vincent.abriou@...com>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/stm: ltdc: remove clk_round_rate comment

Dear Philippe,

you're right, clk_disable() & clk_enable() are necessary with STM32F4 
SOC (not for STM32MP1).

I'll revert this part of the patch.

Many thanks


-- 
Yannick Fertré | TINA: 166 7152 | Tel: +33 244027152 | Mobile: +33 620600270
Microcontrollers and Digital ICs Group | Microcontrolleurs Division

On 5/10/19 6:40 PM, Philippe CORNU wrote:
> Dear Yannick,
> Thank you for your patch,
>
> In your patch, you have removed clk_disable() & clk_enable().
> Could you please double confirm ?
>
> thanks
> Philippe :-)
>
>
> On 5/10/19 5:03 PM, Yannick Fertré wrote:
>> Clk_round_rate returns rounded clock without changing
>> the hardware in any way.
>> This function couldn't replace set_rate/get_rate calls.
>> Todo comment has been removed & a new log inserted.
>>
>> Signed-off-by: Yannick Fertré <yannick.fertre@...com>
>> ---
>>    drivers/gpu/drm/stm/ltdc.c | 10 +++-------
>>    1 file changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
>> index 97912e2..2f8aa2e 100644
>> --- a/drivers/gpu/drm/stm/ltdc.c
>> +++ b/drivers/gpu/drm/stm/ltdc.c
>> @@ -507,20 +507,16 @@ static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
>>    	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
>>    	int rate = mode->clock * 1000;
>>    
>> -	/*
>> -	 * TODO clk_round_rate() does not work yet. When ready, it can
>> -	 * be used instead of clk_set_rate() then clk_get_rate().
>> -	 */
>> -
>> -	clk_disable(ldev->pixel_clk);
>>    	if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
>>    		DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
>>    		return false;
>>    	}
>> -	clk_enable(ldev->pixel_clk);
>>    
>>    	adjusted_mode->clock = clk_get_rate(ldev->pixel_clk) / 1000;
>>    
>> +	DRM_DEBUG_DRIVER("requested clock %dkHz, adjusted clock %dkHz\n",
>> +			 mode->clock, adjusted_mode->clock);
>> +
>>    	return true;
>>    }
>>    
-- 
Yannick Fertré | TINA: 166 7152 | Tel: +33 244027152 | Mobile: +33 620600270
Microcontrollers and Digital ICs Group | Microcontrolleurs Division