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    Subject[PATCH 5.19 0451/1157] drm/radeon: avoid bogus "vram limit (0) must be a power of 2" warning
    Date
    From: Mateusz Jończyk <mat.jonczyk@o2.pl>

    [ Upstream commit 9da2902609f7519c48eda84f953f72fee53f2b71 ]

    I was getting the following message on boot on Linux 5.19-rc5:
    radeon 0000:01:05.0: vram limit (0) must be a power of 2
    (I didn't use any radeon.vramlimit commandline parameter).

    This is caused by
    commit 8c2d34eb53b9 ("drm/radeon: use kernel is_power_of_2 rather than local version")
    which removed radeon_check_pot_argument() and converted its users to
    is_power_of_2(). The two functions differ in its handling of 0, which is
    the default value of radeon_vram_limit: radeon_check_pot_argument()
    "incorrectly" considered it a power of 2, while is_power_of_2() does not.

    An appropriate conditional silences the warning message.

    It is not necessary to add a similar test to other callers of
    is_power_of_2() in radeon_device.c. The matching commit in amdgpu:
    commit 761175078466 ("drm/amdgpu: use kernel is_power_of_2 rather than local version")
    is unaffected by this bug.

    Tested on Radeon HD 3200.

    Not ccing stable, this is not serious enough.

    Fixes: 8c2d34eb53b9 ("drm/radeon: use kernel is_power_of_2 rather than local version")
    Cc: Alex Deucher <alexander.deucher@amd.com>
    Cc: Christian König <christian.koenig@amd.com>
    Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
    Cc: David Airlie <airlied@linux.ie>
    Cc: Daniel Vetter <daniel@ffwll.ch>
    Cc: Jonathan Gray <jsg@jsg.id.au>
    Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/radeon/radeon_device.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
    index 15692cb241fc..429644d5ddc6 100644
    --- a/drivers/gpu/drm/radeon/radeon_device.c
    +++ b/drivers/gpu/drm/radeon/radeon_device.c
    @@ -1113,7 +1113,7 @@ static int radeon_gart_size_auto(enum radeon_family family)
    static void radeon_check_arguments(struct radeon_device *rdev)
    {
    /* vramlimit must be a power of two */
    - if (!is_power_of_2(radeon_vram_limit)) {
    + if (radeon_vram_limit != 0 && !is_power_of_2(radeon_vram_limit)) {
    dev_warn(rdev->dev, "vram limit (%d) must be a power of 2\n",
    radeon_vram_limit);
    radeon_vram_limit = 0;
    --
    2.35.1


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