Patch "clk: meson: mpll: use 64-bit maths in params_from_rate" has been added to the 4.14-stable tree

Patch "clk: meson: mpll: use 64-bit maths in params_from_rate" has been added to the 4.14-stable tree

[gregkh]

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 4.14-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-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Apr  9 13:58:16 CEST 2018
From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date: Sat, 23 Dec 2017 22:38:32 +0100
Subject: clk: meson: mpll: use 64-bit maths in params_from_rate

From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>


[ 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.

Fixes: 007e6e5c5f01d3 ("clk: meson: mpll: add rw operation")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/clk/meson/clk-mpll.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/clk/meson/clk-mpll.c
+++ b/drivers/clk/meson/clk-mpll.c
@@ -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 martin.blumenstingl@googlemail.com are

queue-4.14/clk-meson-mpll-use-64-bit-maths-in-params_from_rate.patch