linux-kernel - Re: [PATCH v11 10/12] drm/mediatek: dpi: Add dpintf support

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Date:   Mon, 13 Jun 2022 12:55:46 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Bo-Chen Chen <rex-bc.chen@...iatek.com>, chunkuang.hu@...nel.org,
        p.zabel@...gutronix.de, daniel@...ll.ch, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, matthias.bgg@...il.com,
        airlied@...ux.ie
Cc:     msp@...libre.com, granquet@...libre.com, jitao.shi@...iatek.com,
        wenst@...omium.org, ck.hu@...iatek.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v11 10/12] drm/mediatek: dpi: Add dpintf support

Il 13/06/22 08:48, Bo-Chen Chen ha scritto:
> From: Guillaume Ranquet <granquet@...libre.com>
> 
> dpintf is the displayport interface hardware unit. This unit is similar
> to dpi and can reuse most of the code.
> 
> This patch adds support for mt8195-dpintf to this dpi driver. Main
> differences are:
>   - Some features/functional components are not available for dpintf
>     which are now excluded from code execution once is_dpintf is set
>   - dpintf can and needs to choose between different clockdividers based
>     on the clockspeed. This is done by choosing a different clock parent.
>   - There are two additional clocks that need to be managed. These are
>     only set for dpintf and will be set to NULL if not supplied. The
>     clk_* calls handle these as normal clocks then.
>   - Some register contents differ slightly between the two components. To
>     work around this I added register bits/masks with a DPINTF_ prefix
>     and use them where different.
> 
> Based on a separate driver for dpintf created by
> Jitao shi <jitao.shi@...iatek.com>.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> [Bo-Chen: Modify reviewers' comments.]
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_dpi.c          | 115 ++++++++++++++++++--
>   drivers/gpu/drm/mediatek/mtk_dpi_regs.h     |  13 +++
>   drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c |   4 +
>   drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h |   1 +
>   drivers/gpu/drm/mediatek/mtk_drm_drv.c      |   3 +
>   5 files changed, 126 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index 6b8cf648a5b5..08c8f21b4421 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -71,6 +71,7 @@ struct mtk_dpi {
>   	void __iomem *regs;
>   	struct device *dev;
>   	struct clk *engine_clk;
> +	struct clk *pll_gate_clk;

You don't need this clock in this driver, at all.

`pll_gate` would be CLK_VDO0_DP_INTF0_DP_INTF (parent = CLK_TOP_EDP);

Currently, you're assigning CLK_TOP_EDP to "pixel", but you can, at this point,
simply assign CLK_VDO0_DP_INTF0_DP_INTF to "pixel" instead... as when you call
clk_prepare_enable() on it, that'll also take care of enabling its CLK_TOP_EDP
parent for you.

You're not doing anything special if not taking care of enabling/disabling it.

Regards,
Angelo