From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v2 4/6] clk: tegra20: init NDFLASH clock to sensible rate Date: Tue, 29 May 2018 15:19:47 +0300 Message-ID: <04cdfdf5-33c5-b569-9cd7-dda1b9ea0baf@gmail.com> References: <20180527215442.14760-5-stefan@agner.ch> <20180528075510.GQ6835@tbergstrom-lnx.Nvidia.com> <5665b799f763daa82dced238fb494863@agner.ch> <20180529074804.GA6708@tbergstrom-lnx.Nvidia.com> <90180dd9fc6e60175c54b9d70e50f0e5@agner.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <90180dd9fc6e60175c54b9d70e50f0e5@agner.ch> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Stefan Agner , Peter De Schrijver Cc: boris.brezillon@bootlin.com, dwmw2@infradead.org, computersforpeace@gmail.com, marek.vasut@gmail.com, robh+dt@kernel.org, mark.rutland@arm.com, thierry.reding@gmail.com, mturquette@baylibre.com, sboyd@kernel.org, dev@lynxeye.de, miquel.raynal@bootlin.com, richard@nod.at, marcel@ziswiler.com, krzk@kernel.org, benjamin.lindqvist@endian.se, jonathanh@nvidia.com, pgaikwad@nvidia.com, mirza.krak@gmail.com, linux-mtd@lists.infradead.org, linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org List-Id: devicetree@vger.kernel.org On 29.05.2018 15:12, Stefan Agner wrote: > On 29.05.2018 09:48, Peter De Schrijver wrote: >> On Mon, May 28, 2018 at 05:53:08PM +0200, Stefan Agner wrote: >>> 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 >>>>> >>>>> 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 >>>>> Signed-off-by: Stefan Agner >>>>> --- >>>>> 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?). >>> >> >> Yes, historically this feature wasn't available, so we used these init tables. >> Unfortunately it's not easy to get rid of them for parent and rate >> configuration, because new kernels should also work with existing DTBs, so we >> can't just add assigned-clock properties and remove the existing table >> entries. What we could do is use the CLK_IS_CRITICAL flag for all clocks which >> are only enabled by the init table. For not yet merged blocks, this is >> ofcourse not a concern. > > Sure I understand. > > Was just somewhat surprised that it isn't used at all yet (grep -r -e > assigned-clock arch/arm/boot/dts/tegra* returns nothing). After all, > assigned clocks bindings have been merged in 2014 :-) > > At least "clk: tegra: Specify VDE clock rate" merged earlier this year > would have been a candidate already. I wasn't even aware of existence of the assigned-clock properties, probably just like others.