Messages in this thread | | | From | Peng Fan <> | Subject | RE: [PATCH] clk: clk-conf: bypass setting rate/parent if already same | Date | Thu, 26 Oct 2023 08:01:45 +0000 |
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> Subject: Re: [PATCH] clk: clk-conf: bypass setting rate/parent if already same > > Hi Peng, > > On Thu, Oct 26, 2023 at 8:35 AM Peng Fan (OSS) <peng.fan@oss.nxp.com> > wrote: > > From: Peng Fan <peng.fan@nxp.com> > > > > If the original rate and parent is already the same as what users > > wanna to configure through assigned clock rate and parent, there is no > > need to configure them again which may cause more cpu cycles or more > > SCMI RPC calls. > > > > So check the rate and parent first, and bypass when the original rate > > and parent are same as requested by device tree node. > > > > Signed-off-by: Peng Fan <peng.fan@nxp.com> > > Thanks for your patch! > > > --- a/drivers/clk/clk-conf.c > > +++ b/drivers/clk/clk-conf.c > > @@ -65,7 +65,11 @@ static int __set_clk_parents(struct device_node > *node, bool clk_supplier) > > goto err; > > } > > > > - rc = clk_set_parent(clk, pclk); > > + if (__clk_get_hw(pclk) != __clk_get_hw(clk_get_parent(clk))) > > + rc = clk_set_parent(clk, pclk); > > + else > > + rc = 0; > > The else branch is not needed, as rc already indicates a non-error condition. > > > + > > if (rc < 0) > > pr_err("clk: failed to reparent %s to %s: %d\n", > > __clk_get_name(clk), > > __clk_get_name(pclk), rc); @@ -112,7 +116,10 @@ static int > __set_clk_rates(struct device_node *node, bool clk_supplier) > > return PTR_ERR(clk); > > } > > > > - rc = clk_set_rate(clk, rate); > > + if (clk_get_rate(clk) != rate) > > + rc = clk_set_rate(clk, rate); > > + else > > + rc = 0; > > Likewise. > > > if (rc < 0) > > pr_err("clk: couldn't set %s clk rate to %u (%d), current > rate: %lu\n", > > __clk_get_name(clk), rate, rc, > > However, one can wonder whether this check should be done in > clk_set_parent() resp. clk_set_rate() instead, so it would benefit all callers?
Yeah, I could do that, but first Let's see whether Stephen is ok with your suggestion or not.
> > Also: > > /** > * clk_get_rate - obtain the current clock rate (in Hz) for a clock source. > * This is only valid once the clock source has been enabled. > * @clk: clock source > */ > > So at least the second part is not guaranteed to work?
I am not sure, but seems there is no clk enabled check in clk_get_rate function.
Thanks, Peng.
> > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux- > m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds
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