Re: [PATCH v6 3/6] drm: sun4i: dsi: Add bridge support

[Maxime Ripard <maxime@cerno.tech>]

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On Fri, Dec 10, 2021 at 04:47:08PM +0530, Jagan Teki wrote:
> Some display panels would come up with a non-DSI output, those
> can have an option to connect the DSI host by means of interface
> bridge converter.
> 
> This DSI to non-DSI interface bridge converter would require
> DSI Host to handle drm bridge functionalities in order to
> communicate interface bridge.
> 
> This patch adds support for bridge functionalities in Allwinner
> DSI controller.
> 
> Supporting down-stream bridge makes few changes in the driver.
> 
> - It drops drm_connector and related operations as drm_bridge_attach
>   creates connector during attachment.
> 
> - It drop panel pointer and iterate the bridge, so-that it can operate
>   the normal bridge and panel_bridge in constitutive callbacks.
> 
> - It uses devm_drm_of_get_bridge for panel or bridge lookup. It uses
>   port 0 and endpoint 0 to support I2C-based bridges eventhough the
>   usual Allwinner DSI OF graph doesn't require this for panel and
>   non-I2C based downstream bridges.
> 
> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> ---
> Changes for v6:
> - support donwstream bridge
> - drop bridge conversion
> - devm_drm_of_get_bridge() require child lookup
> https://patchwork.kernel.org/project/dri-devel/cover/20211207054747.461029-1-jagan@amarulasolutions.com/
> Changes for v5:
> - add atomic APIs
> - find host and device variant DSI devices.
> Changes for v4, v3:
> - none
> 
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 83 ++++++++++----------------
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  9 +--
>  2 files changed, 33 insertions(+), 59 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 9cf91dcac3f2..f1d612bf1a0b 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -21,6 +21,7 @@
>  
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
> @@ -720,6 +721,7 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	struct mipi_dsi_device *device = dsi->device;
>  	union phy_configure_opts opts = { };
>  	struct phy_configure_opts_mipi_dphy *cfg = &opts.mipi_dphy;
> +	struct drm_bridge *iter;
>  	u16 delay;
>  	int err;
>  
> @@ -769,8 +771,10 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	phy_configure(dsi->dphy, &opts);
>  	phy_power_on(dsi->dphy);
>  
> -	if (dsi->panel)
> -		drm_panel_prepare(dsi->panel);
> +	list_for_each_entry(iter, &dsi->bridge_chain, chain_node) {
> +		if (iter->funcs->pre_enable)
> +			iter->funcs->pre_enable(iter);
> +	}

Like we discussed in the previous version already, this is unnecessary,
just like the poking at bridge_chain in the encoder.

Maxime

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