Quoting Anson Huang (2018-09-03 00:20:53)

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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.

Why can't we add clks to the op-tee node in DT's /firmware container?
Then any clks in there can be turned on forever and left enabled by the
linux driver?