Add helpers to convert between q4 fixed point and integer/fraction
values. Also add the format/argument macros required to printk q4 fixed
point variables. The q4 notation is based on the short variant described
by
https://en.wikipedia.org/wiki/Q_(number_format)
where only the number of fraction bits in the fixed point value are
defined, while the full size is deducted from the container type, that
is the size of int for these helpers. Using the fxp_ prefix, which makes
moving these helpers outside of drm to a more generic place easier, if
they prove to be useful.
These are needed by later patches dumping the Display Stream Compression
configuration in DRM core and in the i915 driver to replace the
corresponding bpp_x16 helpers defined locally in the driver.
v2: Use the more generic/descriptive fxp_q4 prefix instead of drm_x16.
(Jani)
Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240628164451.1177612-2-imre.deak@intel.com
As well noted by Pekka[1], the rounding of drm_fixp2int_round is wrong.
To round a number, you need to add 0.5 to the number and floor that,
drm_fixp2int_round() is adding 0.0000076. Make it add 0.5.
[1]: https://lore.kernel.org/all/20240301135327.22efe0dd.pekka.paalanen@collabora.com/
Fixes: 8b25320887d7 ("drm: Add fixed-point helper to get rounded integer values")
Suggested-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240316-drm_fixed-v2-1-c1bc2665b5ed@riseup.net
Unit testing this in VKMS shows that passing 0 into
this function returns -1, which is highly counter-
intuitive. Fix it by checking whether the input is
>= 0 instead of > 0.
Fixes: 64566b5e767f ("drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil")
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108163647.106853-2-harry.wentland@amd.com
Create a new fixed-point helper to allow us to return the rounded value
of our fixed point value.
[v2]:
* Create the function drm_fixp2int_round() (Melissa Wen).
[v3]:
* Use drm_fixp2int() instead of shifting manually (Arthur Grillo).
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230512104044.65034-1-mcanal@igalia.com
Several DRM core and helper source files include drm_crtc_helper.h
without needing it or only to get its transitive include statements;
leading to unnecessary compile-time dependencies.
Directly include required headers and drop drm_crtc_helper.h where
possible. The header file, drm_fixed.h, includes <linux/kernel.h>
for lower_32_bits().
v2:
* include drm_crtc_helper.h in drm_crtc_helper.c (Sam)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230116131235.18917-3-tzimmermann@suse.de
drm_fixp_from_fraction allows us to create a fixed point directly
from a fraction, rather than creating fixed point values and dividing
later. This avoids overflow of our 64 bit value for large numbers.
drm_fixp2int_ceil allows us to return the ceiling of our fixed point
value.
[airlied: squash Jordan's fix]
32-bit-build-fix: Jordan Lazare <Jordan.Lazare@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Sign bit wasn't handled properly and a small typo.
Thanks to Christian for helping me sort this out.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Required for certain driver calculations. Code
was written by Christian König and ported to the
drm by me.
v2: fix 64 bit divides
v3: fix 64 bit for real (math64.h)
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This helper macro retrieves the fractional part of a fixed20_12 20.12
fixed-point number.
Signed-off-by: Robert Morell <rmorell@nvidia.com>
Signed-off-by: Olof Johansson <olofj@chromium.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
