[Bug 110675] Regression: EDP panel flickers with linux 5.1+

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110675

--- Comment #5 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
The immediate difference I see is:
[   12.400643] [drm:intel_dump_pipe_config] dp m_n: lanes: 2; gmch_m: 5146655,
gmch_n: 8388608, link_m: 285925, link_n: 524288, tu: 64
vs.
[   12.465994] [drm:intel_dump_pipe_config] dp m_n: lanes: 2; gmch_m: 20054,
gmch_n: 32768, link_m: 17825, link_n: 32768, tu: 64

Hmm. The relevant commit 53ca2edcf033 ("drm: Change limited M/N quirk to
constant N quirk.") is already in both kernels so these really should be
identical. I can't see how the quirk could get applied to only dp_m2_n2 but not
dp_m_n.

Can you try something silly like:
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7061,7 +7061,7 @@ static void compute_m_n(unsigned int m, unsigned int n,
         * specified fixed N value for asynchronous clock mode,
         * which the devices expect also in synchronous clock mode.
         */
-       if (constant_n)
+       if (1||constant_n)
                *ret_n = 0x8000;
        else
                *ret_n = min_t(unsigned int, roundup_pow_of_two(n),
DATA_LINK_N_MAX);

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