linux-kernel - Re: [PATCH v3 2/2] drm: bridge: Add support for Solomon SSD2825 RGB/DSI bridge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <hz6amgqdmvr6tow5k3gj6n2bnaayejrdv6yhj6sjzs7v3dbjbv@3dcm45ydkkd3>
Date: Mon, 24 Feb 2025 04:10:08 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] drm: bridge: Add support for Solomon SSD2825
 RGB/DSI bridge

On Sun, Feb 23, 2025 at 05:32:44PM +0200, Svyatoslav Ryhel wrote:
> SSD2825 is a cost-effective MIPI Bridge Chip solution targeting mainly
> smartphones. It can convert 24bit RGB interface into 4-lane MIPI-DSI
> interface to drive display modules of up to 800 x 1366, while supporting
> AMOLED, a-si LCD or LTPS panel technologies for smartphone applications.
> 
> Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> ---
>  drivers/gpu/drm/bridge/Kconfig   |  13 +
>  drivers/gpu/drm/bridge/Makefile  |   1 +
>  drivers/gpu/drm/bridge/ssd2825.c | 821 +++++++++++++++++++++++++++++++
>  3 files changed, 835 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/ssd2825.c
> 

> +
> +	if (buf == MIPI_DCS_SET_DISPLAY_ON) {
> +		/*
> +		 * NOTE! This is here since it cannot be called in bridge enable because
> +		 * bridge pre enable and bridge enable have no gap in between.
> +		 *
> +		 * Existing framework bridge-panel seq is:
> +		 *	panel_prepare > bridge_pre_enable > bridge_enable > panel_enable
> +		 *
> +		 * Using prepare_prev_first was tested, but it switches seq like this:
> +		 *	bridge_pre_enable > panel_prepare > bridge_enable > panel_enable
> +		 *
> +		 * This will not work since panel hw MUST be prepared before bridge is
> +		 * configured. Correct seq should be:
> +		 *	panel_prepare > bridge_pre_enable > panel_enable > bridge_enable
> +		 *
> +		 * Last two functions are swapped related to existing framework. I am not
> +		 * aware about method which allows that.
> +		 *
> +		 * Once there will be such method/flag, code below should be moved into
> +		 * bridge_enable since it is basically a bridge configuration completing
> +		 * after initial panel DSI sequence is completed.

Will bridge_pre_enable -> panel_prepare (including
MIPI_DCS_SET_DISPLAY_ON) -> bridge_enable work?

The rest looks good to me.

> +		 */
> +		config = SSD2825_CONF_REG_HS | SSD2825_CONF_REG_DCS |
> +			 SSD2825_CONF_REG_ECD | SSD2825_CONF_REG_EOT;
> +
> +		if (dsi_dev->mode_flags & MIPI_DSI_MODE_VIDEO)
> +			config |= SSD2825_CONF_REG_VEN;
> +
> +		if (dsi_dev->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
> +			config &= ~SSD2825_CONF_REG_EOT;
> +
> +		/* Complete configuration after DSI commands were sent */
> +		ssd2825_write_reg(priv, SSD2825_CONFIGURATION_REG, config);
> +		ssd2825_write_reg(priv, SSD2825_PLL_CTRL_REG, 0x0001);
> +		ssd2825_write_reg(priv, SSD2825_VC_CTRL_REG, 0x0000);
> +	}
> +
> +	return 0;
> +}
> +
> 

-- 
With best wishes
Dmitry