[PATCH 1/7] drm/i915/panel: Fix the pixel clock overflow in the VRR vtotal

[ElXreno <elxreno@gmail.com>]

intel_panel_compute_config_vrr() multiplies the pixel clock in kHz by
1000 in a signed int. A 3840x2400@240 timing has a 2342.4 MHz pixel
clock, the product overflows, and the vertical total computed for a
refresh rate other than that of the fixed mode comes out negative.

Do the multiplication in 64 bits.

This needs a fixed mode above 2147 MHz, so one that uses the joiner,
inside the VRR range of the panel, and a request for another refresh
rate that ends up on that fixed mode, as the allow_modeset=false path
does for a mode that is VRR compatible with the current one.

Fixes: a2da67028cd0 ("drm/i915: Allow arbitrary refresh rates with VRR eDP panels")
Signed-off-by: ElXreno <elxreno@gmail.com>
---
 drivers/gpu/drm/i915/display/intel_panel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 81e638d0c7b3..157be3153c7e 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -277,8 +277,8 @@ static int intel_panel_compute_config_vrr(struct intel_atomic_state *state,
 		int vsync_end_offset = adjusted_mode->vtotal - adjusted_mode->vsync_end;
 
 		adjusted_mode->vtotal =
-			DIV_ROUND_CLOSEST(adjusted_mode->clock * 1000,
-					  adjusted_mode->htotal * vrefresh);
+			DIV_ROUND_CLOSEST_ULL(mul_u32_u32(adjusted_mode->clock, 1000),
+					      adjusted_mode->htotal * vrefresh);
 
 		adjusted_mode->vsync_start = adjusted_mode->vtotal - vsync_start_offset;
 		adjusted_mode->vsync_end = adjusted_mode->vtotal - vsync_end_offset;
-- 
2.56.0