[PATCH 0/2] Fixes in snps-phy HDMI PLL algorithm

[PATCH 0/2] Fixes in snps-phy HDMI PLL algorithm

[Ankit Nautiyal]

Fixes/improvement in snps-phy HDMI PLL algorithm.

Ankit Nautiyal (2):
  drm/i915/snps_hdmi_pll: Fix 64-bit divisor truncation by using
    div64_u64
  drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())

 drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

-- 
2.45.2

[PATCH 1/2] drm/i915/snps_hdmi_pll: Fix 64-bit divisor truncation by using div64_u64

[Ankit Nautiyal]

DIV_ROUND_CLOSEST_ULL uses do_div(), which expects a 32-bit divisor.
When passing a 64-bit constant like CURVE2_MULTIPLIER, the value is
silently truncated to u32, potentially leading to incorrect results
on large divisors.

Replace DIV_ROUND_CLOSEST_ULL with DIV64_U64_ROUND_CLOSEST which correctly
handles full 64-bit division.

v2: Use DIV64_U64_ROUND_CLOSEST instead of div64_u64 macro. (Jani)

Fixes: 5947642004bf ("drm/i915/display: Add support for SNPS PHY HDMI PLL algorithm for DG2")
Reported-by: Vas Novikov <vasya.novikov@gmail.com>
Closes: https://lore.kernel.org/all/8d7c7958-9558-4c8a-a81a-e9310f2d8852@gmail.com/
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Vas Novikov <vasya.novikov@gmail.com>
Cc: <stable@vger.kernel.org> # v6.15+
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c | 4 ++--
 1 file changed, 2 insertions(+), 2 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 74bb3bedf30f..5111bdc3075b 100644
--- a/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
+++ b/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
@@ -103,8 +103,8 @@ static void get_ana_cp_int_prop(u64 vco_clk,
 			    DIV_ROUND_DOWN_ULL(curve_1_interpolated, CURVE0_MULTIPLIER)));
 
 	ana_cp_int_temp =
-		DIV_ROUND_CLOSEST_ULL(DIV_ROUND_DOWN_ULL(adjusted_vco_clk1, curve_2_scaled1),
-				      CURVE2_MULTIPLIER);
+		DIV64_U64_ROUND_CLOSEST(DIV_ROUND_DOWN_ULL(adjusted_vco_clk1, curve_2_scaled1),
+					CURVE2_MULTIPLIER);
 
 	*ana_cp_int = max(1, min(ana_cp_int_temp, 127));
 
-- 
2.45.2

[PATCH 2/2] drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())

[Ankit Nautiyal]

The values of ana_cp_int, and ana_cp_prop are clamped between 1 and 127.
Use the more intuitive and readable clamp() macro instead of using
nested max(min(...)).

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c | 4 ++--
 1 file changed, 2 insertions(+), 2 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 5111bdc3075b..7fe6b4a18213 100644
--- a/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
+++ b/drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c
@@ -106,7 +106,7 @@ static void get_ana_cp_int_prop(u64 vco_clk,
 		DIV64_U64_ROUND_CLOSEST(DIV_ROUND_DOWN_ULL(adjusted_vco_clk1, curve_2_scaled1),
 					CURVE2_MULTIPLIER);
 
-	*ana_cp_int = max(1, min(ana_cp_int_temp, 127));
+	*ana_cp_int = clamp(ana_cp_int_temp, 1, 127);
 
 	curve_2_scaled_int = curve_2_scaled1 * (*ana_cp_int);
 
@@ -125,7 +125,7 @@ static void get_ana_cp_int_prop(u64 vco_clk,
 						       curve_1_interpolated);
 
 	*ana_cp_prop = DIV64_U64_ROUND_UP(adjusted_vco_clk2, curve_2_scaled2);
-	*ana_cp_prop = max(1, min(*ana_cp_prop, 127));
+	*ana_cp_prop = clamp(*ana_cp_prop, 1, 127);
 }
 
 static void compute_hdmi_tmds_pll(u64 pixel_clock, u32 refclk,
-- 
2.45.2

Re: [PATCH 2/2] drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH 2/2] drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())
Link: https://lore.kernel.org/stable/20250618130951.1596587-3-ankit.k.nautiyal%40intel.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 0/2] Fixes in snps-phy HDMI PLL algorithm

[Jani Nikula]

On Wed, 18 Jun 2025, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
> Fixes/improvement in snps-phy HDMI PLL algorithm.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

>
> Ankit Nautiyal (2):
>   drm/i915/snps_hdmi_pll: Fix 64-bit divisor truncation by using
>     div64_u64
>   drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())
>
>  drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

-- 
Jani Nikula, Intel

Re: [PATCH 0/2] Fixes in snps-phy HDMI PLL algorithm

[Nautiyal, Ankit K]

On 6/19/2025 1:21 AM, Jani Nikula wrote:
> On Wed, 18 Jun 2025, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
>> Fixes/improvement in snps-phy HDMI PLL algorithm.
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>

Thank you once again, Jani, for pointing out the sparse warning and for 
your reviews.

The series has been pushed to drm-intel-next.

Regards,

Ankit

>
>> Ankit Nautiyal (2):
>>    drm/i915/snps_hdmi_pll: Fix 64-bit divisor truncation by using
>>      div64_u64
>>    drm/i915/snps_hdmi_pll: Use clamp() instead of max(min())
>>
>>   drivers/gpu/drm/i915/display/intel_snps_hdmi_pll.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)