drm/amd/display: fix MALL hysteresis timer underflow at high refresh rates

dcn30_apply_idle_power_optimizations() derives the MALL frame cache
hysteresis timer with

tmr_delay = (uint32_t)(div_u64(

drm/amd/display: fix MALL hysteresis timer underflow at high refresh rates

dcn30_apply_idle_power_optimizations() derives the MALL frame cache
hysteresis timer with

tmr_delay = (uint32_t)(div_u64(..., denom) - 64LL);

div_u64() returns a u64, so when the quotient is smaller than 64 the
subtraction wraps instead of going negative and tmr_delay ends up huge.
The loop that follows tries to squeeze it into the 6 bit register field
by doubling denom, but that only makes the quotient smaller, so tmr_delay
can never converge. tmr_scale is bumped past 3 and the function gives up
with

/* Delay exceeds range of hysteresis timer */
ASSERT(false);

even though the requested delay is too *short* to encode, not too long.

With mall_additional_timer_percent left at its default of 0, the quotient
drops below 64 once the refresh rate used for the calculation goes above
~243 Hz. Every DCN 3.0 display above that loses MALL static screen
entirely and splats a WARN once per boot. Reproduced on Navi 23
(RX 6600) driving 1920x1080, resetting /sys/kernel/debug/clear_warn_once
between modes:

refresh MALL ASSERT
144 Hz enabled no
240 Hz enabled no
280 Hz skipped yes
360 Hz skipped yes

Commit 3bb68cec4db8 ("drm/amd/display: Add Overflow check to skip MALL")
already covered the other end of the range, where a large stutter period
makes the delay too long to encode. Cover the short end by clamping to
0, which selects the shortest hysteresis the register can express,
65.28us * 64 = ~4.18ms. That is marginally longer than what the formula
asks for at these refresh rates, and erring long is the safe direction:
it only delays MALL entry, it can never enter early.

The numerator does not change between iterations, only denom does, so
compute it once and keep both call sites inside 100 columns.

The genuinely out of range case at very low refresh rates still reaches
the ASSERT, which is where it belongs.

Fixes: 52f2e83e2fe5 ("drm/amdgpu/display: add MALL support (v2)")
Signed-off-by: Francis Marlou Pacaro <pacaro.francis.marlou.n@gmail.com>
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 387550e53e1405f1f960b62b22f8783db17c8e1d)

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drm/amd/display: Fix NULL dereference in dcn50/dcn60 init_hw

dc->clk_mgr is checked for NULL earlier in dcn50_init_hw() and
dcn60_init_hw(), but dcn50_initialize_min_clocks() and
dcn401_initialize_m

drm/amd/display: Fix NULL dereference in dcn50/dcn60 init_hw

dc->clk_mgr is checked for NULL earlier in dcn50_init_hw() and
dcn60_init_hw(), but dcn50_initialize_min_clocks() and
dcn401_initialize_min_clocks() are called without any guard,
causing Smatch to report potential NULL dereferences.

Guard both call sites with the same pattern used throughout
both functions:

if (dc->clk_mgr && dc->clk_mgr->funcs)

Also fix dcn50_initialize_min_clocks() which calls
get_dispclk_from_dentist without checking the function pointer,
unlike the dcn401 equivalent which guards that call.

Fix kernel-doc in dcn60_hwseq.c by adding missing parameter descriptions
for @probe in dcn60_update_probe_status() and @type in
is_probe_measurement_type_for_hubbub().

Fixes: 7f7d7ea1fa51 ("drm/amd/display: Add new sources for DCN6")
Reported-by: Dan Carpenter <error27@gmail.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Ivan Lipski <ivan.lipski@amd.com>
Cc: Dan Wheeler <daniel.wheeler@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 325c9a827cdd748e126eafeadaffc556204773d2)

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