linux-kernel - Re: [PATCH v6 3/3] drm/stm: ltdc: add lvds pixel clock

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Date: Fri, 28 Jun 2024 14:45:34 +0200
From: Philippe CORNU <philippe.cornu@...s.st.com>
To: Yannick FERTRE <yannick.fertre@...s.st.com>,
        Raphael Gallais-Pou
	<raphael.gallais-pou@...s.st.com>,
        David Airlie <airlied@...il.com>, Daniel
 Vetter <daniel@...ll.ch>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre
 Torgue <alexandre.torgue@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>
CC: <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 3/3] drm/stm: ltdc: add lvds pixel clock


On 6/21/24 16:55, Yannick FERTRE wrote:
> Hi Raphaël,
> 
> Thanks for your patch, it will not merged due to a new clock management.
> 
> Philippe,
> 
> this patch will be replaced by another which manages all clocks that the 
> display controller
> 
>   will need (pixel clock, bus clock reference clock).

Hi Raphaël & Yannick,
I applied 1 & 2 on drm-misc-next.
Many thanks,
Philippe :-)


> 
> 
> Best regards
> 
> 
> Le 26/02/2024 à 11:48, Raphael Gallais-Pou a écrit :
>> The STM32MP25x display subsystem presents a mux which feeds the loopback
>> pixel clock of the current bridge in use into the LTDC. This mux is only
>> accessible through sysconfig registers which is not yet available in the
>> STM32MP25x common clock framework.
>>
>> While waiting for a complete update of the clock framework, this would
>> allow to use the LVDS.
>>
>> Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
>> Signed-off-by: Yannick Fertre <yannick.fertre@...s.st.com>
>> ---
>> Changes in v2:
>>     - Fixed my address
>>     - Fixed smatch warning
>> ---
>>   drivers/gpu/drm/stm/ltdc.c | 19 +++++++++++++++++++
>>   drivers/gpu/drm/stm/ltdc.h |  1 +
>>   2 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
>> index 5576fdae4962..23011a8913bd 100644
>> --- a/drivers/gpu/drm/stm/ltdc.c
>> +++ b/drivers/gpu/drm/stm/ltdc.c
>> @@ -838,6 +838,12 @@ ltdc_crtc_mode_valid(struct drm_crtc *crtc,
>>       int target_max = target + CLK_TOLERANCE_HZ;
>>       int result;
>> +    if (ldev->lvds_clk) {
>> +        result = clk_round_rate(ldev->lvds_clk, target);
>> +        DRM_DEBUG_DRIVER("lvds pixclk rate target %d, available %d\n",
>> +                 target, result);
>> +    }
>> +
>>       result = clk_round_rate(ldev->pixel_clk, target);
>>       DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, 
>> result);
>> @@ -1896,6 +1902,8 @@ void ltdc_suspend(struct drm_device *ddev)
>>       DRM_DEBUG_DRIVER("\n");
>>       clk_disable_unprepare(ldev->pixel_clk);
>> +    if (ldev->lvds_clk)
>> +        clk_disable_unprepare(ldev->lvds_clk);
>>   }
>>   int ltdc_resume(struct drm_device *ddev)
>> @@ -1910,6 +1918,13 @@ int ltdc_resume(struct drm_device *ddev)
>>           DRM_ERROR("failed to enable pixel clock (%d)\n", ret);
>>           return ret;
>>       }
>> +    if (ldev->lvds_clk) {
>> +        if (clk_prepare_enable(ldev->lvds_clk)) {
>> +            clk_disable_unprepare(ldev->pixel_clk);
>> +            DRM_ERROR("Unable to prepare lvds clock\n");
>> +            return -ENODEV;
>> +        }
>> +    }
>>       return 0;
>>   }
>> @@ -1981,6 +1996,10 @@ int ltdc_load(struct drm_device *ddev)
>>           }
>>       }
>> +    ldev->lvds_clk = devm_clk_get(dev, "lvds");
>> +    if (IS_ERR(ldev->lvds_clk))
>> +        ldev->lvds_clk = NULL;
>> +
>>       rstc = devm_reset_control_get_exclusive(dev, NULL);
>>       mutex_init(&ldev->err_lock);
>> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
>> index 9d488043ffdb..4a60ce5b610c 100644
>> --- a/drivers/gpu/drm/stm/ltdc.h
>> +++ b/drivers/gpu/drm/stm/ltdc.h
>> @@ -44,6 +44,7 @@ struct ltdc_device {
>>       void __iomem *regs;
>>       struct regmap *regmap;
>>       struct clk *pixel_clk;    /* lcd pixel clock */
>> +    struct clk *lvds_clk;    /* lvds pixel clock */
>>       struct mutex err_lock;    /* protecting error_status */
>>       struct ltdc_caps caps;
>>       u32 irq_status;
>>