[PATCH 2/2] clk: imx: imx7d: remove clks_init_on array

Hi, Stephen

Anson Huang
Best Regards!

-----Original Message-----
From: Stephen Boyd <sboyd@kernel.org>
Sent: Friday, August 31, 2018 9:29 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;
Anson Huang [off-list ref]; Fabio Estevam
[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 Peng Fan (2018-08-12 18:15:41)

quoted

Hi Anson,

quoted

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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.

quoted

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.

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.

quoted

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?

 
Yes, I agree with you, OP-TEE should maintain its clocks when OP-TEE is enabled.

This is ONLY a concern raised by Peng, all platforms' current clock driver does NOT consider
this case, so I think this patch should be fine for now? Thanks.

Anson.