linux-kernel - Re: [PATCH v2] drm: bridge: synopsys/dw-hdmi: Provide default configuration function for HDMI 2.0 PHY

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Date:   Fri, 7 Jul 2017 16:47:32 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Archit Taneja <architt@...eaurora.org>
CC:     <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Mark Yao <mark.yao@...k-chips.com>,
        Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        Heiko Stübner <heiko@...ech.de>
Subject: Re: [PATCH v2] drm: bridge: synopsys/dw-hdmi: Provide default
 configuration function for HDMI 2.0 PHY

Hi Archit,


On 23-06-2017 10:36, Jose Abreu wrote:
> Currently HDMI 2.0 PHYs do not have a default configuration function.
>
> As *some* of the HDMI 2.0 PHYs have the same register layout as the 3D
> PHYs we can provide the same default configuration function for both
> and still let user overwrite this with custom configuration function
> if needed.
>
> If, for some reason, the PHY is custom or has a register different
> register layout then custom configuration function *must* be provided
> in order for the system to work correctly. As we prefer the pdata
> provided configuration function over the internal one this change
> will not make any impact in custom platforms.
>
> This patch is based on today's drm-misc-next branch.
>
> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
> Tested-by: Mark Yao <mark.yao@...k-chips.com>

This is needed for RK3399 support. Can you please apply it?

Best regards,
Jose Miguel Abreu

> Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> Cc: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Mark Yao <mark.yao@...k-chips.com>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Heiko Stübner <heiko@...ech.de>
>
> Changes in v2:
> 	- Rebased and refrased commit message
> ---
>
> Hi All,
>
> There as been a little confusion about dw-hdmi phys so I will expand a little bit
> here so that I can base my decision about this patch and why does it only works
> in some platforms.
>
> First, if you read dw-hdmi.c code, you will see that there is an identification
> register for the phy type being used. Unfortunatelly, this only states the phy type
> and not the phy version.
>
> Second, we have many HDMI 2.0 phys (so, same phy type: 0xf3) but, as you may have guessed,
> HW team decided to change regbank between some versions.
>
> Third and last, each phy in a SoC has unique characteristics, so each phy (event if
> they are the same version) will have different PLL configuration parameters.
>
> Given all this I managed to conclude that Mark's phy is still an HDMI 2.0 phy but with
> the same register layout as previous 3D PHY's. I found at least 2 phys with the same
> register layout and only 1 phy which has a different layout, so I think majority wins
> here and we should let the default configuration function for HDMI 2.0 phys be the same
> one as the 3D.
>
> Short story: There is no way to correctly identify, at runtime, the phy version being
> used by the controller so we can't provide a default configuration function. We can,
> however assume that most of the HDMI 2.0 phys will have the 3D layout BUT each developer
> must confirm that the layout in its SoC is the expected one and if not, provide a custom
> configuration function.
>
> Best regards,
> Jose Miguel Abreu
>
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index ead1124..10c8d8c 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2170,6 +2170,7 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
>  		.name = "DWC HDMI 2.0 TX PHY",
>  		.gen = 2,
>  		.has_svsret = true,
> +		.configure = hdmi_phy_configure_dwc_hdmi_3d_tx,
>  	}, {
>  		.type = DW_HDMI_PHY_VENDOR_PHY,
>  		.name = "Vendor PHY",