linux-kernel - Re: [PATCH v7 2/3] drm/bridge: ti-sn65dsi83: Add ti,lvds-vod-swing optional properties

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Message-ID: <75aewnwpb6y73gqlrqmelzeia7bdar5ihm3ety5gfjaqalkuby@gwv4xjpomoit>
Date: Mon, 16 Dec 2024 11:59:33 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Andrej Picej <andrej.picej@...ik.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, airlied@...il.com, 
	simona@...ll.ch, maarten.lankhorst@...ux.intel.com, mripard@...nel.org, 
	tzimmermann@...e.de, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, 
	festevam@...il.com, marex@...x.de, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, upstream@...ts.phytec.de
Subject: Re: [PATCH v7 2/3] drm/bridge: ti-sn65dsi83: Add ti,lvds-vod-swing
 optional properties

On Mon, Dec 16, 2024 at 09:54:09AM +0100, Andrej Picej wrote:
> Add a optional properties to change LVDS output voltage. This should not
> be static as this depends mainly on the connected display voltage
> requirement. We have three properties:
> - "ti,lvds-termination-ohms", which sets near end termination,
> - "ti,lvds-vod-swing-data-microvolt" and
> - "ti,lvds-vod-swing-clock-microvolt" which both set LVDS differential
> output voltage for data and clock lanes. They are defined as an array
> with min and max values. The appropriate bitfield will be set if
> selected constraints can be met.
> 
> If "ti,lvds-termination-ohms" is not defined the default of 200 Ohm near
> end termination will be used. Selecting only one:
> "ti,lvds-vod-swing-data-microvolt" or
> "ti,lvds-vod-swing-clock-microvolt" can be done, but the output voltage
> constraint for only data/clock lanes will be met. Setting both is
> recommended.
> 
> Signed-off-by: Andrej Picej <andrej.picej@...ik.com>
> ---
> Changes in v7:
> - decrement refcount of the endpoint in all error cases,
> - add spaces to improve the readability of the long if statement conditions in
> sn65dsi83_select_lvds_vod_swing.
> Changes in v6:
> - rework termination resistor logic, default is now set by resistor value, not
> reg value,
> - move setting lvds_vod_swing_conf to default value of 0x1 inside if statement
> which checks if both properties are not set
> Changes in v5:
> - specify default values in sn65dsi83_parse_lvds_endpoint,
> - move sn65dsi83_parse_lvds_endpoint for channel B up, outside if,
> Changes in v4:
> - fix typo in commit message bitfiled -> bitfield
> - use arrays (lvds_vod_swing_conf and lvds_term_conf) in private data, instead
> of separate variables for channel A/B
> - add more checks on return value of "of_property_read_u32_array"
> Changes in v3:
> - use microvolts for default array values 1000 mV -> 1000000 uV.
> Changes in v2:
> - use datasheet tables to get the proper configuration
> - since major change was done change the authorship to myself
> ---
>  drivers/gpu/drm/bridge/ti-sn65dsi83.c | 145 +++++++++++++++++++++++++-
>  1 file changed, 142 insertions(+), 3 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

-- 
With best wishes
Dmitry