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Revision d2e3fce9ddafe689c6f7cb355f23560637e30b9d authored by Ville Syrjälä on 10 November 2020, 21:04:47 UTC, committed by Rodrigo Vivi on 19 November 2020, 06:52:25 UTC 
drm/i915: Handle max_bpc==16
 
EDID can declare the maximum supported bpc up to 16,
and apparently there are displays that do so. Currently
we assume 12 bpc is tha max. Fix the assumption and
toss in a MISSING_CASE() for any other value we don't
expect to see.

This fixes modesets with a display with EDID max bpc > 12.
Previously any modeset would just silently fail on platforms
that didn't otherwise limit this via the max_bpc property.
In particular we don't add the max_bpc property to HDMI
ports on gmch platforms, and thus we would see the raw
max_bpc coming from the EDID.

I suppose we could already adjust this to also allow 16bpc,
but seeing as no current platform supports that there is
little point.

Cc: stable@vger.kernel.org
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2632
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201110210447.27454-1-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
(cherry picked from commit 2ca5a7b85b0c2b97ef08afbd7799b022e29f192e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
1 parent b5462cc
Raw File
lm77.rst 
Kernel driver lm77
==================

Supported chips:

  * National Semiconductor LM77

    Prefix: 'lm77'

    Addresses scanned: I2C 0x48 - 0x4b

    Datasheet: Publicly available at the National Semiconductor website

	       http://www.national.com/


Author: Andras BALI <drewie@freemail.hu>

Description
-----------

The LM77 implements one temperature sensor. The temperature
sensor incorporates a band-gap type temperature sensor,
10-bit ADC, and a digital comparator with user-programmable upper
and lower limit values.

The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and
critical (temp1_crit.) It also implements an hysteresis mechanism which
applies to all 3 limits. The relative difference is stored in a single
register on the chip, which means that the relative difference between
the limit and its hysteresis is always the same for all 3 limits.

This implementation detail implies the following:

* When setting a limit, its hysteresis will automatically follow, the
  difference staying unchanged. For example, if the old critical limit
  was 80 degrees C, and the hysteresis was 75 degrees C, and you change
  the critical limit to 90 degrees C, then the hysteresis will
  automatically change to 85 degrees C.
* All 3 hysteresis can't be set independently. We decided to make
  temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are
  read-only. Setting temp1_crit_hyst writes the difference between
  temp1_crit_hyst and temp1_crit into the chip, and the same relative
  hysteresis applies automatically to the low and high limits.
* The limits should be set before the hysteresis.
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