linux-kernel - Re: [RFC PATCH 4/6] drm/bridge/nwl-dsi: Drop mux handling

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Message-ID: <20200528195717.GA568887@bogus>
Date:   Thu, 28 May 2020 13:57:17 -0600
From:   Rob Herring <robh@...nel.org>
To:     Guido Günther <agx@...xcpu.org>
Cc:     Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Anson Huang <Anson.Huang@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Peng Fan <peng.fan@....com>,
        Robert Chiras <robert.chiras@....com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 4/6] drm/bridge/nwl-dsi: Drop mux handling

On Fri, May 15, 2020 at 03:12:13PM +0200, Guido Günther wrote:
> This will be handled via the mux-input-bridge.

You can't do this. What happens booting a kernel with this change and an 
un-modified dtb? You just broke it.

> 
> Signed-off-by: Guido Günther <agx@...xcpu.org>
> ---
>  drivers/gpu/drm/bridge/Kconfig   |  1 -
>  drivers/gpu/drm/bridge/nwl-dsi.c | 61 --------------------------------
>  2 files changed, 62 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 3886c0f41bdd..11444f841e35 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -78,7 +78,6 @@ config DRM_NWL_MIPI_DSI
>  	select DRM_PANEL_BRIDGE
>  	select GENERIC_PHY_MIPI_DPHY
>  	select MFD_SYSCON
> -	select MULTIPLEXER
>  	select REGMAP_MMIO
>  	help
>  	  This enables the Northwest Logic MIPI DSI Host controller as
> diff --git a/drivers/gpu/drm/bridge/nwl-dsi.c b/drivers/gpu/drm/bridge/nwl-dsi.c
> index b14d725bf609..8839f333f39c 100644
> --- a/drivers/gpu/drm/bridge/nwl-dsi.c
> +++ b/drivers/gpu/drm/bridge/nwl-dsi.c
> @@ -12,7 +12,6 @@
>  #include <linux/math64.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/module.h>
> -#include <linux/mux/consumer.h>
>  #include <linux/of.h>
>  #include <linux/of_platform.h>
>  #include <linux/phy/phy.h>
> @@ -44,9 +43,6 @@ enum transfer_direction {
>  	DSI_PACKET_RECEIVE,
>  };
>  
> -#define NWL_DSI_ENDPOINT_LCDIF 0
> -#define NWL_DSI_ENDPOINT_DCSS 1
> -
>  struct nwl_dsi_plat_clk_config {
>  	const char *id;
>  	struct clk *clk;
> @@ -94,7 +90,6 @@ struct nwl_dsi {
>  	struct reset_control *rst_esc;
>  	struct reset_control *rst_dpi;
>  	struct reset_control *rst_pclk;
> -	struct mux_control *mux;
>  
>  	/* DSI clocks */
>  	struct clk *phy_ref_clk;
> @@ -1018,14 +1013,6 @@ static int nwl_dsi_parse_dt(struct nwl_dsi *dsi)
>  	}
>  	dsi->tx_esc_clk = clk;
>  
> -	dsi->mux = devm_mux_control_get(dsi->dev, NULL);
> -	if (IS_ERR(dsi->mux)) {
> -		ret = PTR_ERR(dsi->mux);
> -		if (ret != -EPROBE_DEFER)
> -			DRM_DEV_ERROR(dsi->dev, "Failed to get mux: %d\n", ret);
> -		return ret;
> -	}
> -
>  	base = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(base))
>  		return PTR_ERR(base);
> @@ -1073,47 +1060,6 @@ static int nwl_dsi_parse_dt(struct nwl_dsi *dsi)
>  	return 0;
>  }
>  
> -static int nwl_dsi_select_input(struct nwl_dsi *dsi)
> -{
> -	struct device_node *remote;
> -	u32 use_dcss = 1;
> -	int ret;
> -
> -	remote = of_graph_get_remote_node(dsi->dev->of_node, 0,
> -					  NWL_DSI_ENDPOINT_LCDIF);
> -	if (remote) {
> -		use_dcss = 0;
> -	} else {
> -		remote = of_graph_get_remote_node(dsi->dev->of_node, 0,
> -						  NWL_DSI_ENDPOINT_DCSS);
> -		if (!remote) {
> -			DRM_DEV_ERROR(dsi->dev,
> -				      "No valid input endpoint found\n");
> -			return -EINVAL;
> -		}
> -	}
> -
> -	DRM_DEV_INFO(dsi->dev, "Using %s as input source\n",
> -		     (use_dcss) ? "DCSS" : "LCDIF");
> -	ret = mux_control_try_select(dsi->mux, use_dcss);
> -	if (ret < 0)
> -		DRM_DEV_ERROR(dsi->dev, "Failed to select input: %d\n", ret);
> -
> -	of_node_put(remote);
> -	return ret;
> -}

You could however make these functions generic for any bridge to use. 
Define a function that checks for mux-control property and if found sets 
up the mux (IIRC, there's already a concept of a default state). That 
should be callable from somewhere generic too.

Rob