linux-kernel - Re: [PATCH v2 2/4] drivers: clk: zynqmp: Fix divider2 calculation

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Message-ID: <159054128348.88029.11223617733496629973@swboyd.mtv.corp.google.com>
Date:   Tue, 26 May 2020 18:01:23 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jolly Shah <jolly.shah@...inx.com>, arm@...nel.org,
        linux-clk@...r.kernel.org, michal.simek@...inx.com,
        mturquette@...libre.com, olof@...om.net
Cc:     rajanv@...inx.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Tejas Patel <tejas.patel@...inx.com>,
        Jolly Shah <jolly.shah@...inx.com>
Subject: Re: [PATCH v2 2/4] drivers: clk: zynqmp: Fix divider2 calculation

Quoting Jolly Shah (2020-03-02 13:50:41)
> From: Tejas Patel <tejas.patel@...inx.com>
> 
> zynqmp_get_divider2_val() calculates, divider value of type DIV2 clock,
> considering best possible combination of DIV1 and DIV2.
> 
> To find best possible values of DIV1 and DIV2, DIV1's parent rate
> should be consider and not DIV2's parent rate since it would rate of
> div1 clock. Consider a below topology,
> 
>         out_clk->div2_clk->div1_clk->fixed_parent
> 
> where out_clk = (fixed_parent/div1_clk) / div2_clk, so parent clock
> of div1_clk (i.e. out_clk) should be divided by div1_clk and div2_clk.
> 
> Existing code divides parent rate of div2_clk's clock instead of
> div1_clk's parent rate, which is wrong.
> 
> Fix the same by considering div1's parent clock rate.
> 
> Fixes: 4ebd92d2e228 ("clk: zynqmp: Fix divider calculation")
> Signed-off-by: Tejas Patel <tejas.patel@...inx.com>
> Signed-off-by: Jolly Shah <jolly.shah@...inx.com>
> ---

Applied to clk-next