[PATCH v8 7/7] clk: rockchip: implement proper GATE_LINK support

[Sebastian Reichel]

Hi Dmitry,

On Fri, Jan 26, 2024 at 10:36:13PM +0300, Dmitry Osipenko wrote:
> On 1/26/24 21:18, Sebastian Reichel wrote:
> > Recent Rockchip SoCs have a new hardware block called Native Interface
> > Unit (NIU), which gates clocks to devices behind them. These effectively
> > need two parent clocks.
> > 
> > GATE_LINK type clocks handle the second parent via 'linkedclk' by using
> > runtime PM clocks. To make that possible a new platform device is created
> > for every clock handled in this way.
> > 
> > Note, that before this patch clk_rk3588_probe() has never been called,
> > because CLK_OF_DECLARE marks the DT node as processed. This patch replaces
> > that with CLK_OF_DECLARE_DRIVER and thus the probe function is used now.
> > This is necessary to have 'struct device' available.
> > 
> > Also instead of builtin_platform_driver_probe, the driver has been
> > switched to use core_initcall, since it should be fully probed before
> > the Rockchip PM domain driver (and that is using postcore_initcall).
> 
> Why clk driver needs to be fully probed before PD? The PD driver
> shouldn't probe until all clk providers that it uses are registered, and
> then both clk and PD should be registered at the default level.

The error handling in the rockchip PD driver needs rework to
properly handle -EPROBE_DEFER, which I consider a separate series.

Note, that the driver currently has 'builtin_platform_driver_probe',
but does not actually probe anything. All clocks are registered via
CLK_OF_DECLARE, which happens even before core_initcall. So this
does not make things worse.

Also the OF node is marked as initialized by the early clocks
(CLK_OF_DECLARE_DRIVER) via the call to of_clk_add_provider(). This
is necessary, since otherwise the early clocks cannot be referenced
and we need the early clocks for the timer registration (so it's not
possible to move all the clocks to late init). This effectively
results in fw_devlink not working properly. It will tell PM domain
driver too early, that it may start probing (so a bunch of useless
-EPROBE_DEFER will happen).

Greetings,

-- Sebastian
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