linux-kernel - Re: [PATCH 0/3] pwm-backlight: add subdrivers & Tegra support

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Date:	Sun, 20 Jan 2013 11:38:04 +0800
From:	Mark Zhang <markz@...dia.com>
To:	Alexandre Courbot <acourbot@...dia.com>
CC:	Thierry Reding <thierry.reding@...onic-design.de>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"gnurou@...il.com" <gnurou@...il.com>
Subject: Re: [PATCH 0/3] pwm-backlight: add subdrivers & Tegra support

Yeah, thanks Alex. :)

So this is a non power sequence version of backlight & panel enabling,
isn't it? I remember we talked about this several days ago and you
mentioned kernel guys want an ad-hoc version(power sequence logics
inside driver, not in DT) and I believe this is it, right?

I think finally I can enable Tegra30 cardhu's display after this patch
merged.

Mark
On 01/19/2013 06:30 PM, Alexandre Courbot wrote:
> This series introduces a way to use pwm-backlight hooks with platforms
> that use the device tree through a subdriver system. It also adds support
> for the Tegra-based Ventana board, adding the last missing block to enable
> its panel. Support for other Tegra board can thus be easily added.
> 
> I have something else in mind to properly support this (power
> sequences), but this work relies on the GPIO subsystem redesign which will
> take some time. The pwm-backlight subdrivers can do the job by the meantime.
> 
> There are a few design points that might need to be discussed:
> 1) Link order is important: subdrivers register themselves in their
> module_init function, which must be called before pwm-backlight's probe.
> This forbids linking subdrivers as separate modules from pwm-backlight.
> 2) The subdriver's data is temporarily passed through the backlight
> device's driver data. This should not hurt, but maybe there is a better way
> to do this.
> 3) Subdrivers must add themselves into pwm-backlight's own of_device_id
> table. It would be cleaner to not have to list subdrivers into
> pwm-backlight's main file, but I cannot think of a way to do otherwise.
> 
> Suggestions for the 3 points listed above are very welcome - in any case,
> I hope to make this converge into something mergeable quickly.
> 
> Note that these patches are the last missing block to get a functional
> panel on Tegra boards. Using 3.8rc4 and these patches, the internal panel
> on Ventana is usable out-of-the-box. Yay.
> 
> Alexandre Courbot (3):
>   pwm-backlight: add subdriver mechanism
>   tegra: pwm-backlight: add tegra pwm-bl driver
>   tegra: ventana: of: add host1x device to DT
> 
>  arch/arm/boot/dts/tegra20-ventana.dts  |  29 +++++-
>  arch/arm/configs/tegra_defconfig       |   1 +
>  drivers/video/backlight/Kconfig        |   7 ++
>  drivers/video/backlight/Makefile       |   4 +
>  drivers/video/backlight/pwm_bl.c       |  70 ++++++++++++++-
>  drivers/video/backlight/pwm_bl_tegra.c | 159 +++++++++++++++++++++++++++++++++
>  include/linux/pwm_backlight.h          |  15 ++++
>  7 files changed, 281 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/video/backlight/pwm_bl_tegra.c
> 
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