linux-kernel - Re: [PATCH v1 1/1] drm/mediatek/dp: The register is written with the parsed DTS SSC value.

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Message-ID: <bc785b80e109fc04c5973ee4efad115e0c3907c4.camel@mediatek.com>
Date: Thu, 11 Apr 2024 06:30:50 +0000
From: LIANKUN YANG (杨连坤) <Liankun.Yang@...iatek.com>
To: "krzk@...nel.org" <krzk@...nel.org>, "kishon@...nel.org"
	<kishon@...nel.org>, "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
	Mac Shen (沈俊) <Mac.Shen@...iatek.com>,
	Chunfeng Yun (云春峰) <Chunfeng.Yun@...iatek.com>,
	Jitao Shi (石记涛) <jitao.shi@...iatek.com>,
	"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>, "vkoul@...nel.org"
	<vkoul@...nel.org>, "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>, "linux-phy@...ts.infradead.org"
	<linux-phy@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] drm/mediatek/dp: The register is written with the
 parsed DTS SSC value.

On Wed, 2024-04-03 at 16:56 +0200, Krzysztof Kozlowski wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 03/04/2024 08:41, Krzysztof Kozlowski wrote:
> > On 03/04/2024 06:05, Liankun Yang wrote:
> >> [Description]
> >> Severe screen flickering has been observed on the external display
> >> when the DP projection function is used with the market expansion
> dock.
> >>
> > 
> >> +if (!strcmp(mode_name, RG_XTP_GLB_TXPLL_SSC_DELTA_RBR)) {
> >> +regmap_update_bits(dp_phy->regs, ssc_reg_offset,
> >> +   XTP_GLB_TXPLL_SSC_DELTA_RBR_DEFAULT, read_value);
> >> +} else if (!strcmp(mode_name, RG_XTP_GLB_TXPLL_SSC_DELTA_HBR)) {
> >> +read_value = read_value << 16 | 0x0000;
> >> +regmap_update_bits(dp_phy->regs, ssc_reg_offset,
> >> +   XTP_GLB_TXPLL_SSC_DELTA_HBR_DEFAULT, read_value);
> >> +}
> >> +
> >> +return 0;
> >> +}
> >> +
> >> +static struct device_node *mtk_dp_get_ssc_node(struct phy *phy,
> struct mtk_dp_phy *dp_phy)
> >> +{
> >> +struct device_node *mode_node = NULL;
> >> +
> >> +mode_node = of_find_node_by_name(dp_phy->dev->of_node,
> SSC_SETTING);
> > 
> > ?!?!
> > You have the node, why do you try to find it?
> > 
> 
> Wait, that was brainfuck from my side or -ENOCOFFEE. Ignore.
> 
> I still have a question though, where did you document new ABI:
> dependency on the node name here?
> 
> Also, why you are not going through direct children -
> of_get_child_by_name()?
> 
> Best regards,
> Krzysztof
> 
> 

Sorry, there is formatting issue in the previous email.

The dp_phy device has already been registered through the
mtk_dp_register_phy function in the mtk_dp.c file, 
so it cannot be redefined in the dts. Avoid using of_get_child_by_name
for this purpose.

To find the node name, utilize of_find_node_by_name since it has
already been registered.

Best regards,
Liankun Yang
>