From mboxrd@z Thu Jan  1 00:00:00 1970
From: jbrunet@baylibre.com (Jerome Brunet)
Date: Sat, 23 Dec 2017 23:28:51 +0100
Subject: [PATCH] clk: meson: mpll: use 64-bit maths in params_from_rate
In-Reply-To: <20171223213832.16552-1-martin.blumenstingl@googlemail.com>
References: <20171223213832.16552-1-martin.blumenstingl@googlemail.com>
Message-ID: <1514068131.4333.1.camel@baylibre.com>
To: linus-amlogic@lists.infradead.org
List-Id: linus-amlogic.lists.infradead.org

On Sat, 2017-12-23 at 22:38 +0100, Martin Blumenstingl wrote:
> "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>

Good catch !

Applied to next/drivers