[PATCH] clk: sunxi-ng: ccu_mp: fix clocks without P dividers

[Enzo Adriano <enzo.adriano.code@gmail.com>]

Some sunxi-ng MP clocks have an M divider but no P divider. The A523
MBUS, IOMMU and DRAM clocks use this layout and also require the update
bit when changing their rate.

ccu_mp_set_rate() unconditionally builds and applies a mask for the P
field. With a zero-width P field this produces an invalid GENMASK()
range and can clear bits outside a P divider, including the clock gate.

The callback also ignores CCU_FEATURE_UPDATE_BIT, so hardware that
requires the update bit may not latch the new divider value.

Only update the P field when it exists, and set CCU_SUNXI_UPDATE_BIT for
MP clocks carrying the feature. This matches the existing sunxi-ng div,
mux and gate helper behavior.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/r/20260712081341.9D1431F00A3D@smtp.kernel.org
Fixes: 6702d17f54a8 ("clk: sunxi-ng: a523: add video mod clocks")
Assisted-by: Codex:gpt-5
Signed-off-by: Enzo Adriano <enzo.adriano.code@gmail.com>
---
Based on clk-next 8cdeaa50eae8 (Linux 7.2-rc2).
Tested with strict checkpatch and an arm64 W=1 build of ccu_mp.o.
No hardware runtime claim is made.

 drivers/clk/sunxi-ng/ccu_mp.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu_mp.c b/drivers/clk/sunxi-ng/ccu_mp.c
index 7cdb0eedc69b..aa6cb20447f1 100644
--- a/drivers/clk/sunxi-ng/ccu_mp.c
+++ b/drivers/clk/sunxi-ng/ccu_mp.c
@@ -237,12 +237,17 @@ static int ccu_mp_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	reg = readl(cmp->common.base + cmp->common.reg);
 	reg &= ~GENMASK(cmp->m.width + cmp->m.shift - 1, cmp->m.shift);
-	reg &= ~GENMASK(cmp->p.width + cmp->p.shift - 1, cmp->p.shift);
+	if (cmp->p.width)
+		reg &= ~GENMASK(cmp->p.width + cmp->p.shift - 1, cmp->p.shift);
+	if (cmp->common.features & CCU_FEATURE_UPDATE_BIT)
+		reg |= CCU_SUNXI_UPDATE_BIT;
 	reg |= (m - cmp->m.offset) << cmp->m.shift;
-	if (shift)
-		reg |= ilog2(p) << cmp->p.shift;
-	else
-		reg |= (p - cmp->p.offset) << cmp->p.shift;
+	if (cmp->p.width) {
+		if (shift)
+			reg |= ilog2(p) << cmp->p.shift;
+		else
+			reg |= (p - cmp->p.offset) << cmp->p.shift;
+	}
 
 	writel(reg, cmp->common.base + cmp->common.reg);
 
-- 
2.53.0