linux-kernel - Re: [PATCH v2 4/6] clk: tegra20: init NDFLASH clock to sensible rate

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Date:   Mon, 28 May 2018 17:58:11 +0200
From:   Lucas Stach <dev@...xeye.de>
To:     Stefan Agner <stefan@...er.ch>,
        Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     boris.brezillon@...tlin.com, dwmw2@...radead.org,
        computersforpeace@...il.com, marek.vasut@...il.com,
        robh+dt@...nel.org, mark.rutland@....com, thierry.reding@...il.com,
        mturquette@...libre.com, sboyd@...nel.org,
        miquel.raynal@...tlin.com, richard@....at, marcel@...wiler.com,
        krzk@...nel.org, digetx@...il.com, benjamin.lindqvist@...ian.se,
        jonathanh@...dia.com, pgaikwad@...dia.com, mirza.krak@...il.com,
        linux-mtd@...ts.infradead.org, linux-tegra@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 4/6] clk: tegra20: init NDFLASH clock to sensible rate

Am Montag, den 28.05.2018, 17:53 +0200 schrieb Stefan Agner:
> On 28.05.2018 09:55, Peter De Schrijver wrote:
> > On Sun, May 27, 2018 at 11:54:40PM +0200, Stefan Agner wrote:
> > > From: Lucas Stach <dev@...xeye.de>
> > > 
> > > Set up the NAND Flash controller clock to run at 150MHz
> > > instead of the rate set by the bootloader. This is a
> > > conservative rate which also yields good performance.
> > > 
> > > Signed-off-by: Lucas Stach <dev@...xeye.de>
> > > Signed-off-by: Stefan Agner <stefan@...er.ch>
> > > ---
> > >  drivers/clk/tegra/clk-tegra20.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/clk/tegra/clk-tegra20.c b/drivers/clk/tegra/clk-tegra20.c
> > > index 0ee56dd04cec..dff8c425cd28 100644
> > > --- a/drivers/clk/tegra/clk-tegra20.c
> > > +++ b/drivers/clk/tegra/clk-tegra20.c
> > > @@ -1049,6 +1049,7 @@ static struct tegra_clk_init_table init_table[] __initdata = {
> > >  	{ TEGRA20_CLK_GR2D, TEGRA20_CLK_PLL_C, 300000000, 0 },
> > >  	{ TEGRA20_CLK_GR3D, TEGRA20_CLK_PLL_C, 300000000, 0 },
> > >  	{ TEGRA20_CLK_VDE, TEGRA20_CLK_CLK_MAX, 300000000, 0 },
> > > +	{ TEGRA20_CLK_NDFLASH, TEGRA20_CLK_PLL_P, 150000000, 0 },
> > >  	/* must be the last entry */
> > >  	{ TEGRA20_CLK_CLK_MAX, TEGRA20_CLK_CLK_MAX, 0, 0 },
> > >  };
> > > --
> > > 2.17.0
> > > 
> > 
> > Maybe better to specify this in the Tegra20 dtsi? See 
> > "Assigned clock parents and rates" in
> > Documentation/devicetree/bindings/clock/clock-bindings.txt
> 
> assigned-clocks indeed works just fine for this case. Thanks for
> bringing this up, will drop this patch and add the device tree
> properties in v3.
> 
> Hm, interesting that none of the Tegra device tree make use of the
> feature so far. I guess there would be other cases where this would be
> useful as well (the one just above, VDE?).

Most of the Tegra clock init stuff (including this patch) was written
before we had assigned-clocks as some common DT facility. But fully
agree on dropping this patch.

Regards,
Lucas