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

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Date:   Mon, 23 Oct 2023 20:38:46 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jay Buddhabhatti <jay.buddhabhatti@....com>, michal.simek@....com,
        mturquette@...libre.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 1/2] drivers: clk: zynqmp: calculate closest mux rate

Quoting Jay Buddhabhatti (2023-10-16 04:30:01)
> 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
> 
> Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@....com>
> ---

Any Fixes tag here?