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

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Date:   Mon, 28 May 2018 17:53:08 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     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, dev@...xeye.de,
        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

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?).

--
Stefan