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Anson Huang
Best Regards!

-----Original Message-----
From: Anson Huang
Sent: Monday, September 3, 2018 3:21 PM
To: Stephen Boyd <sboyd@kernel.org>; kernel at pengutronix.de;
linux-arm-kernel at lists.infradead.org; linux-clk at vger.kernel.org;
linux-kernel at vger.kernel.org; mturquette at baylibre.com;
s.hauer at pengutronix.de; shawnguo at kernel.org; Fabio Estevam
[off-list ref]; Jerome Forissier [off-list ref];
Peng Fan [off-list ref]; Rob Herring [off-list ref]
Cc: dl-linux-imx <redacted>
Subject: RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array



Anson Huang
Best Regards!

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-----Original Message-----
From: Stephen Boyd <sboyd@kernel.org>
Sent: Saturday, September 1, 2018 1:58 AM
To: kernel at pengutronix.de; linux-arm-kernel at lists.infradead.org;
linux-clk at vger.kernel.org; linux-kernel at vger.kernel.org;
mturquette at baylibre.com; s.hauer at pengutronix.de;

shawnguo at kernel.org;

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Anson Huang [off-list ref]; Fabio Estevam
[off-list ref]; Jerome Forissier
[off-list ref]; Peng Fan [off-list ref]; Rob
Herring [off-list ref]
Cc: dl-linux-imx <redacted>
Subject: Re: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array

Quoting Jerome Forissier (2018-08-31 01:01:44)

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On 08/31/2018 03:29 AM, Stephen Boyd wrote:

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Quoting Peng Fan (2018-08-12 18:15:41)

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Hi Anson,

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-----Original Message-----
From: Anson Huang
Sent: 2018?8?8? 12:39
To: shawnguo at kernel.org; s.hauer at pengutronix.de;
kernel at pengutronix.de; Fabio Estevam [off-list ref];
mturquette at baylibre.com; sboyd at kernel.org;
linux-arm-kernel at lists.infradead.org;
linux-clk at vger.kernel.org; linux-kernel at vger.kernel.org
Cc: dl-linux-imx <redacted>
Subject: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on
array

Clock framework will enable those clocks registered with
CLK_IS_CRITICAL flag, so no need to have clks_init_on array
during clock

initialization now.

Will it be more flexible to parse dts saying "critical-clocks = <xxx>"
or "init-on-arrary=<xxx>"
and enable those clocks?

Parsing the clocks arrays from dtb is another way of enabling
critical clocks, but for current i.MX6/7 platforms, we implement
it in same way as most of other SoCs, currently I did NOT see
any necessity of putting them in dtb, just adding flag during
clock registering is more simple, if there is any special
requirement for different clocks set to be enabled, then we can
add support to enable

the method of parsing critical-clocks from dtb. Just my two cents.

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Thinking about OP-TEE want to use one device, but it's clocks are
registered by Linux, because there is no module in Linux side use
it, it will shutdown the clock, which cause OP-TEE could not
access the

device.

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Then people have to modify clk code to add CLK_IS_CRITICAL flag
to make sure the clocks are not shutdown by Linux.

However adding a new property in clk node and let driver code
parse the dts, there is no need to modify clk driver code when
OP-TEE needs

another device clock.

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If OP-TEE needs linux to keep things on then why can't the OP-TEE
driver in Linux probe, acquire clocks, and keep the clks enabled forever?

Sounds reasonable, but how could this be done without introducing
platform-specific stuff in the OP-TEE driver?

Why is that a goal?

I do NOT think we should consider such case in this patch series, whatever
OP-TEE needs for its own feature, it should do necessary operations either in its
driver or somewhere else by adding new patch.

Anson.