Patch "clk: meson: mpll: use 64-bit maths in params_from_rate" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

clk: meson: mpll: use 64-bit maths in params_from_rate

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
clk-meson-mpll-use-64-bit-maths-in-params_from_rate.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Martin Blumenstingl <[email protected]>
Date: Sat, 23 Dec 2017 22:38:32 +0100
Subject: clk: meson: mpll: use 64-bit maths in params_from_rate

From: Martin Blumenstingl <[email protected]>

[ Upstream commit 86aacdca66774051cbc0958110a48074b57a060b ]

"rem * SDM_DEN" can easily overflow on the 32-bit Meson8 and Meson8b SoCs if the "remainder" (after the division operation) is greater than 262143Hz. This is likely to happen since the input clock for the MPLLs on Meson8 and Meson8b is "fixed_pll", which is running at a rate of 2550MHz.

One example where this was observed to be problematic was the Ethernet clock calculation (which takes MPLL2 as input). When requesting a rate of 125MHz there is a remainder of 2500000Hz.
The resulting MPLL2 rate before this patch was 127488329Hz. The resulting MPLL2 rate after this patch is 124999103Hz.

Commit b609338b26f5 ("clk: meson: mpll: use 64bit math in rate_from_params") already fixed a similar issue in rate_from_params.

---
 drivers/clk/meson/clk-mpll.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -98,7 +98,7 @@ static void params_from_rate(unsigned lo
 		*sdm = SDM_DEN - 1;
 	} else {
 		*n2 = div;
-		*sdm = DIV_ROUND_UP(rem * SDM_DEN, requested_rate);
+		*sdm = DIV_ROUND_UP_ULL((u64)rem * SDM_DEN, requested_rate);
 	}
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/clk-meson-mpll-use-64-bit-maths-in-params_from_rate.patch