On 9/1/2018 1:10 AM, Stephen Boyd wrote:
Quoting Zhu, Yi Xin (2018-08-28 23:56:22)
On 8/28/2018 3:09 AM, Stephen Boyd wrote:
Quoting yixin zhu (2018-08-08 01:52:20)
On 8/8/2018 1:50 PM, Stephen Boyd wrote:
+/* clock flags definition */
+#define CLOCK_FLAG_VAL_INIT BIT(16)
+#define GATE_CLK_HW BIT(17)
+#define GATE_CLK_SW BIT(18)
+#define GATE_CLK_VT BIT(19)
What does VT mean? Virtual?
Yes. VT means virtual here.
Will change to GATE_CLK_VIRT.
Is it a hardware concept? Or virtualization with hypervisor?
Some peripheral drivers want to use same code cross platforms.
But not all platforms provide HW gate clock. So in this case, clock
driver creates
a virtual gate clock to make it work if no HW gate clock in the SoC.
That's not how things are supposed to work. If a clk isn't there in the
hardware we don't make them up in software so that the consumer software
drivers can keep requesting clks on different platforms. On a different
platform, the driver needs to know that the clks aren't there with a
different compatible string.
OK. Will remove virtual gate clock.
+}
+
+CLK_OF_DECLARE(intel_grx500_cgu, "intel,grx500-cgu", grx500_clk_init);
Any reason a platform driver can't be used instead of CLK_OF_DECLARE()?
It provides CPU clock which is used in early boot stage.
Ok. What is the CPU clock doing in early boot stage? Some sort of timer
frequency? If the driver can be split into two pieces, one to handle the
really early stuff that must be in place to get timers up and running
and the other to register the rest of the clks that aren't critical from
a regular platform driver it would be good. That's preferred model if
something is super critical.
Yes, CPU clock is providing CPU frequency in the early boot stage.
Will put the non-critical clocks in the platform driver.
Sure the CPU clock is handling frequency, but does that matter for early
boot to get going? If timers aren't involved here then it doesn't sound
like this needs CLK_OF_DECLARE.
Yes, timer is involved here.
CPU frequency get by early stage platform code used in clockevent
registration.
