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* [PATCH] drm/i915/display: Fix u32 overflow in SNPS PHY HDMI PLL setup
@ 2025-05-28  6:45 Dibin Moolakadan Subrahmanian
  2025-05-28 13:52 ` ✓ i915.CI.BAT: success for " Patchwork
                   ` (4 more replies)
  0 siblings, 5 replies; 6+ messages in thread
From: Dibin Moolakadan Subrahmanian @ 2025-05-28  6:45 UTC (permalink / raw)
  To: intel-gfx, intel-xe; +Cc: ankit.k.nautiyal

When configuring the HDMI PLL, calculations use DIV_ROUND_UP_ULL and
DIV_ROUND_DOWN_ULL macros, which internally rely on do_div. However, do_div
expects a 32-bit (u32) divisor, and at higher data rates, the divisor can
exceed this limit. This leads to incorrect division results and
ultimately misconfigured PLL values.
This fix replaces do_div calls with  div64_base64 calls where diviser
can exceed u32 limit.

Signed-off-by: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Fixes: 5947642004bf ("drm/i915/display: Add support for SNPS PHY HDMI PLL algorithm for DG2")
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
---
 .../gpu/drm/i915/display/intel_snps_hdmi_pll.c   | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c b/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
index c6321dafef4f..74bb3bedf30f 100644
--- a/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
+++ b/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
@@ -41,12 +41,12 @@ static s64 interp(s64 x, s64 x1, s64 x2, s64 y1, s64 y2)
 {
 	s64 dydx;
 
-	dydx = DIV_ROUND_UP_ULL((y2 - y1) * 100000, (x2 - x1));
+	dydx = DIV64_U64_ROUND_UP((y2 - y1) * 100000, (x2 - x1));
 
-	return (y1 + DIV_ROUND_UP_ULL(dydx * (x - x1), 100000));
+	return (y1 + DIV64_U64_ROUND_UP(dydx * (x - x1), 100000));
 }
 
-static void get_ana_cp_int_prop(u32 vco_clk,
+static void get_ana_cp_int_prop(u64 vco_clk,
 				u32 refclk_postscalar,
 				int mpll_ana_v2i,
 				int c, int a,
@@ -115,16 +115,16 @@ static void get_ana_cp_int_prop(u32 vco_clk,
 								      CURVE0_MULTIPLIER));
 
 	scaled_interpolated_sqrt =
-			int_sqrt(DIV_ROUND_UP_ULL(interpolated_product, vco_div_refclk_float) *
+			int_sqrt(DIV64_U64_ROUND_UP(interpolated_product, vco_div_refclk_float) *
 			DIV_ROUND_DOWN_ULL(1000000000000ULL, 55));
 
 	/* Scale vco_div_refclk for ana_cp_int */
 	scaled_vco_div_refclk2 = DIV_ROUND_UP_ULL(vco_div_refclk_float, 1000000);
-	adjusted_vco_clk2 = 1460281 * DIV_ROUND_UP_ULL(scaled_interpolated_sqrt *
+	adjusted_vco_clk2 = 1460281 * DIV64_U64_ROUND_UP(scaled_interpolated_sqrt *
 						       scaled_vco_div_refclk2,
 						       curve_1_interpolated);
 
-	*ana_cp_prop = DIV_ROUND_UP_ULL(adjusted_vco_clk2, curve_2_scaled2);
+	*ana_cp_prop = DIV64_U64_ROUND_UP(adjusted_vco_clk2, curve_2_scaled2);
 	*ana_cp_prop = max(1, min(*ana_cp_prop, 127));
 }
 
@@ -165,10 +165,10 @@ static void compute_hdmi_tmds_pll(u64 pixel_clock, u32 refclk,
 	/* Select appropriate v2i point */
 	if (datarate <= INTEL_SNPS_PHY_HDMI_9999MHZ) {
 		mpll_ana_v2i = 2;
-		tx_clk_div = ilog2(DIV_ROUND_DOWN_ULL(INTEL_SNPS_PHY_HDMI_9999MHZ, datarate));
+		tx_clk_div = ilog2(div64_u64(INTEL_SNPS_PHY_HDMI_9999MHZ, datarate));
 	} else {
 		mpll_ana_v2i = 3;
-		tx_clk_div = ilog2(DIV_ROUND_DOWN_ULL(INTEL_SNPS_PHY_HDMI_16GHZ, datarate));
+		tx_clk_div = ilog2(div64_u64(INTEL_SNPS_PHY_HDMI_16GHZ, datarate));
 	}
 	vco_clk = (datarate << tx_clk_div) >> 1;
 
-- 
2.43.0


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end of thread, other threads:[~2025-06-03 16:31 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2025-05-28  6:45 [PATCH] drm/i915/display: Fix u32 overflow in SNPS PHY HDMI PLL setup Dibin Moolakadan Subrahmanian
2025-05-28 13:52 ` ✓ i915.CI.BAT: success for " Patchwork
2025-05-28 16:36 ` ✗ i915.CI.Full: failure " Patchwork
2025-06-02  6:44 ` ✓ i915.CI.Full: success " Patchwork
2025-06-03  7:53 ` [PATCH] " Nautiyal, Ankit K
2025-06-03 16:30 ` Nautiyal, Ankit K

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