Hi Jerome,

On Mon, Sep 23, 2019 at 11:29 AM Jerome Brunet [off-list ref] wrote:

On Sat 21 Sep 2019 at 17:12, Martin Blumenstingl [off-list ref] wrote:

quoted

So far the HHI clock controller has been providing the XTAL clock on
Amlogic Meson8/Meson8b/Meson8m2 SoCs.
This is not correct because the XTAL is actually a crystal on the
boards and the SoC has a dedicated input for it.

This updates the dt-bindings of the HHI clock controller and defines
a fixed-clock in meson.dtsi (along with switching everything over to
use this clock).
The clock driver needs three updates to use this:
- patch #2 uses clk_hw_set_parent in the CPU clock notifier. This drops
  the explicit reference to CLKID_XTAL while at the same time making
  the code much easier (thanks to Neil for providing this new method
  as part of the G12A CPU clock bringup!)
- patch #3 ensures that the clock driver doesn't rely on it's internal
  XTAL clock while not losing support for older .dtbs that don't have
  the XTAL clock input yet
- with patch #4 the clock controller's own XTAL clock is not registered
  anymore when a clock input is provided via OF

This series is a functional no-op. It's main goal is to better represent
how the actual hardware looks like.

I'm a bit unsure about this series.

On one hand, I totally agree with you ... having the xtal in DT is the
right way to do it ... when done from the start

yep

On the other hand, things have been this way for years, they are working
and going for xtal in DT does not solve any pending issue. Doing this
means adding complexity in the driver to support both methods. It is
also quite a significant change in DT :/

my two main motivations were:
- keeping the 32-bit SoCs as similar as possible to the 64-bit ones in
terms of "how are the [clock] drivers implemented"
- with the DDR clock controller the .dts looked weird: &ddr_clkc took
CLKID_XTAL from &clkc as input and &clkc took DDR_CLKID_DDR_PLL as
input from &ddr_clkc

RE complexity in the driver to support both:
I still have a cleanup of the meson8b.c init code on my TODO-list
because we're still supporting .dtbs without parent syscon
my plan is to drop that code-path along with the newly added fallback
for "skip CLKID_XTAL" (assuming this is accepted) together for v5.6 or
v5.7


Martin

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