linux-kernel - Re: [PATCH v1 04/10] phy: phy-rockchip-samsung-hdptx: Add support for eDP mode

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Message-ID: <4260470.1IzOArtZ34@diego>
Date: Wed, 27 Nov 2024 10:29:09 +0100
From: Heiko Stübner <heiko@...ech.de>
To: Damon Ding <damon.ding@...k-chips.com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 rfoss@...nel.org, vkoul@...nel.org, sebastian.reichel@...labora.com,
 cristian.ciocaltea@...labora.com, l.stach@...gutronix.de,
 andy.yan@...k-chips.com, hjc@...k-chips.com, algea.cao@...k-chips.com,
 kever.yang@...k-chips.com, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org, Damon Ding <damon.ding@...k-chips.com>,
 sebastian.reichel@...labora.com
Subject:
 Re: [PATCH v1 04/10] phy: phy-rockchip-samsung-hdptx: Add support for eDP
 mode

Hi Damon,

Am Mittwoch, 27. November 2024, 08:51:51 CET schrieb Damon Ding:
> Add basic support for RBR/HBR/HBR2 link rates, and the voltage swing and
> pre-emphasis configurations of each link rate have been verified according
> to the eDP 1.3 requirements.
> 
> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
> ---

[ ... huge block of DP phy support ...]

yes that block was huge, but I also don't see a way to split that up in a
useful way, so it should be fine.


> +static int rk_hdptx_phy_set_mode(struct phy *phy, enum phy_mode mode,
> +				 int submode)
> +{
> +	return 0;
> +}

I think it might make sense to go the same way as the DCPHY and also
naneng combophy, to use #phy-cells = 1 to select the phy-mode via DT .

See [0] for Sebastians initial suggestion regarding the DC-PHY.
The naneng combophy already uses that scheme of mode-selection too.

There is of course the issue of backwards-compatibility, but that can be
worked around in the binding with something like:

 '#phy-cells':
    enum: [0, 1]
    description: |
      If #phy-cells is 0, PHY mode is set to PHY_TYPE_HDMI
      If #phy-cells is 1 mode is set in the PHY cells. Supported modes are:
        - PHY_TYPE_HDMI
        - PHY_TYPE_DP
      See include/dt-bindings/phy/phy.h for constants.

PHY_TYPE_HDMI needs to be added to include/dt-bindings/phy/phy.h
but PHY_TYPE_DP is already there.

That way we would standardize on one form of accessing phy-types
on rk3588 :-) .

Also see the Mediatek CSI rx phy doing this too already [1]


Heiko

[0] https://lore.kernel.org/linux-rockchip/udad4qf3o7kt45nuz6gxsvsmprh4rnyfxfogopmih6ucznizih@7oj2jrnlfonz/
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml