linux-kernel - Re: [PATCH RESEND v2 1/2] drivers: clk: zynqmp: calculate closest mux rate

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Message-ID: <3ddba76f5f44a7b32c5852094667d189.sboyd@kernel.org>
Date: Sat, 16 Dec 2023 17:21:19 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Jay Buddhabhatti <jay.buddhabhatti@....com>, michal.simek@....com, mturquette@...libre.com, shubhrajyoti.datta@...inx.com
Cc: linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Jay Buddhabhatti <jay.buddhabhatti@....com>
Subject: Re: [PATCH RESEND v2 1/2] drivers: clk: zynqmp: calculate closest mux rate

Quoting Jay Buddhabhatti (2023-11-29 03:29:15)
> Currently zynqmp clock driver is not calculating closest mux rate and
> because of that Linux is not setting proper frequency for CPU and
> not able to set given frequency for dynamic frequency scaling.
> 
> E.g., In current logic initial acpu clock parent and frequency as below
> apll1                  0    0    0  2199999978    0     0  50000      Y
>     acpu0_mux          0    0    0  2199999978    0     0  50000      Y
>         acpu0_idiv1    0    0    0  2199999978    0     0  50000      Y
>             acpu0      0    0    0  2199999978    0     0  50000      Y
> 
> After changing acpu frequency to 549999994 Hz using CPU freq scaling its
> selecting incorrect parent which is not closest frequency.
> rpll_to_xpd            0    0    0  1599999984    0     0  50000      Y
>     acpu0_mux          0    0    0  1599999984    0     0  50000      Y
>         acpu0_div1     0    0    0   533333328    0     0  50000      Y
>             acpu0      0    0    0   533333328    0     0  50000      Y
> 
> Parent should remain same since 549999994 = 2199999978 / 4.
> 
> So use __clk_mux_determine_rate_closest() generic function to calculate
> closest rate for mux clock. After this change its selecting correct
> parent and correct clock rate.
> apll1                  0    0    0  2199999978    0     0  50000      Y
>     acpu0_mux          0    0    0  2199999978    0     0  50000      Y
>         acpu0_div1     0    0    0   549999995    0     0  50000      Y
>             acpu0      0    0    0   549999995    0     0  50000      Y
> 
> Fixes: 3fde0e16d016 ("drivers: clk: Add ZynqMP clock driver")
> Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@....com>
> ---

Applied to clk-next