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Date:   Tue, 10 Dec 2019 08:51:11 +0000
From:   Lee Jones <lee.jones@linaro.org>
To:     Hans de Goede <hdegoede@redhat.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Ville =?iso-8859-1?Q?Syrj=E4l=E4?= 
        <ville.syrjala@linux.intel.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-acpi@vger.kernel.org,
        intel-gfx <intel-gfx@lists.freedesktop.org>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] mfd: intel_soc_pmic: Rename pwm_backlight pwm-lookup
 to pwm_pmic_backlight
Message-ID: <20191210085111.GQ3468@dell>
References: <20191119151818.67531-1-hdegoede@redhat.com>
 <20191119151818.67531-3-hdegoede@redhat.com>
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On Tue, 19 Nov 2019, Hans de Goede wrote:

> At least Bay Trail (BYT) and Cherry Trail (CHT) devices can use 1 of 2
> different PWM controllers for controlling the LCD's backlight brightness.
> 
> Either the one integrated into the PMIC or the one integrated into the
> SoC (the 1st LPSS PWM controller).
> 
> So far in the LPSS code on BYT we have skipped registering the LPSS PWM
> controller "pwm_backlight" lookup entry when a Crystal Cove PMIC is
> present, assuming that in this case the PMIC PWM controller will be used.
> 
> On CHT we have been relying on only 1 of the 2 PWM controllers being
> enabled in the DSDT at the same time; and always registered the lookup.
> 
> So far this has been working, but the correct way to determine which PWM
> controller needs to be used is by checking a bit in the VBT table and
> recently I've learned about 2 different BYT devices:
> Point of View MOBII TAB-P800W
> Acer Switch 10 SW5-012
> 
> Which use a Crystal Cove PMIC, yet the LCD is connected to the SoC/LPSS
> PWM controller (and the VBT correctly indicates this), so here our old
> heuristics fail.
> 
> Since only the i915 driver has access to the VBT, this commit renames
> the "pwm_backlight" lookup entries for the Crystal Cove PMIC's PWM
> controller to "pwm_pmic_backlight" so that the i915 driver can do a
> pwm_get() for the right controller depending on the VBT bit, instead of
> the i915 driver relying on a "pwm_backlight" lookup getting registered
> which magically points to the right controller.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/mfd/intel_soc_pmic_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

For my own reference:
  Acked-for-MFD-by: Lee Jones <lee.jones@linaro.org>

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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