linux-kernel - Re: [PATCH v5 02/10] drm/bridge: synopsys: Add DW DPTX Controller support library

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Message-ID: <svn2p46qguxrpn6fhqnjffqpgv7keabwgld53uw6ckkn4piu47@gedy4t22cqfx>
Date: Fri, 25 Jul 2025 18:22:55 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Andy Yan <andyshrk@....com>
Cc: heiko@...ech.de, hjc@...k-chips.com, mripard@...nel.org, naoki@...xa.com,
        stephen@...xa.com, cristian.ciocaltea@...labora.com,
        neil.armstrong@...aro.org, Laurent.pinchart@...asonboard.com,
        yubing.zhang@...k-chips.com, krzk+dt@...nel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, robh@...nel.org,
        sebastian.reichel@...labora.com, Andy Yan <andy.yan@...k-chips.com>
Subject: Re: [PATCH v5 02/10] drm/bridge: synopsys: Add DW DPTX Controller
 support library

On Wed, Jul 16, 2025 at 06:04:29PM +0800, Andy Yan wrote:
> From: Andy Yan <andy.yan@...k-chips.com>
> 
> The DW DP TX Controller is compliant with the DisplayPort Specification
> Version 1.4 with the following features:
> 
> * DisplayPort 1.4a
> * Main Link: 1/2/4 lanes
> * Main Link Support 1.62Gbps, 2.7Gbps, 5.4Gbps and 8.1Gbps
> * AUX channel 1Mbps
> * Single Stream Transport(SST)
> * Multistream Transport (MST)
> * Type-C support (alternate mode)
> * HDCP 2.2, HDCP 1.3
> * Supports up to 8/10 bits per color component
> * Supports RBG, YCbCr4:4:4, YCbCr4:2:2, YCbCr4:2:0
> * Pixel clock up to 594MHz
> * I2S, SPDIF audio interface
> 
> Add library with common helpers to make it can be shared with
> other SoC.
> 
> Signed-off-by: Andy Yan <andy.yan@...k-chips.com>
> 
> ---
> 
> Changes in v5:
> - Use drm_dp_read_sink_count_cap instead of the private implementation.
> 
> Changes in v4:
> - Drop unnecessary header files
> - Switch to devm_drm_bridge_alloc
> 
> Changes in v3:
> - Rebase on drm-misc-next
> - Switch to common helpers to power up/down dp link
> - Only pass parameters to phy that should be set
> 
> Changes in v2:
> - Fix compile error when build as module
> - Add phy init
> - Only use one dw_dp_link_train_set
> - inline dw_dp_phy_update_vs_emph
> - Use dp_sdp
> - Check return value of drm_modeset_lock
> - Merge code in atomic_pre_enable/mode_fixup to atomic_check
> - Return NULL if can't find a supported output format
> - Fix max_link_rate from plat_data
> 
>  drivers/gpu/drm/bridge/synopsys/Kconfig  |    7 +
>  drivers/gpu/drm/bridge/synopsys/Makefile |    1 +
>  drivers/gpu/drm/bridge/synopsys/dw-dp.c  | 2044 ++++++++++++++++++++++
>  include/drm/bridge/dw_dp.h               |   20 +
>  4 files changed, 2072 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/synopsys/dw-dp.c
>  create mode 100644 include/drm/bridge/dw_dp.h
> +
> +static int dw_dp_link_parse(struct dw_dp *dp, struct drm_connector *connector)
> +{
> +	struct dw_dp_link *link = &dp->link;
> +	u8 dpcd;
> +	int ret;
> +
> +	dw_dp_link_reset(link);
> +
> +	ret = drm_dp_read_dpcd_caps(&dp->aux, link->dpcd);
> +	if (ret < 0)
> +		return ret;
> +
> +	drm_dp_read_desc(&dp->aux, &link->desc, drm_dp_is_branch(link->dpcd));
> +
> +	if (drm_dp_read_sink_count_cap(connector, link->dpcd, &link->desc)) {
> +		ret = drm_dp_read_sink_count(&dp->aux);
> +		if (ret < 0)
> +			return ret;
> +
> +		link->sink_count = ret;
> +
> +		/* Dongle connected, but no display */
> +		if (!link->sink_count)
> +			return -ENODEV;
> +	}
> +
> +	ret = drm_dp_dpcd_readb(&dp->aux, DP_DPRX_FEATURE_ENUMERATION_LIST, &dpcd);
> +	if (ret < 0)
> +		return ret;
> +
> +	link->vsc_sdp_supported = !!(dpcd & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED);


drm_dp_vsc_sdp_supported()

> +
> +	link->revision = link->dpcd[DP_DPCD_REV];
> +	link->rate = min_t(u32, min(dp->plat_data.max_link_rate,
> +				    dp->phy->attrs.max_link_rate * 100),
> +			   drm_dp_max_link_rate(link->dpcd));
> +	link->lanes = min_t(u8, phy_get_bus_width(dp->phy),
> +			    drm_dp_max_lane_count(link->dpcd));
> +
> +	link->caps.enhanced_framing = drm_dp_enhanced_frame_cap(link->dpcd);
> +	link->caps.tps3_supported = drm_dp_tps3_supported(link->dpcd);
> +	link->caps.tps4_supported = drm_dp_tps4_supported(link->dpcd);
> +	link->caps.fast_training = drm_dp_fast_training_cap(link->dpcd);
> +	link->caps.channel_coding = drm_dp_channel_coding_supported(link->dpcd);
> +	link->caps.ssc = !!(link->dpcd[DP_MAX_DOWNSPREAD] & DP_MAX_DOWNSPREAD_0_5);
> +
> +	return 0;
> +}
> +

-- 
With best wishes
Dmitry