Re: clk mess on omap4460 with mpu clock

[Andreas Kemnade <andreas@kemnade.info>]

Am Tue, 24 Sep 2024 17:53:17 +0100
schrieb "Russell King (Oracle)" <linux@armlinux.org.uk>:

> On Mon, Sep 23, 2024 at 02:04:47PM +0200, Andreas Kemnade wrote:
> > So the way forward is to check whether that registration is really
> > needed at:
> > https://elixir.bootlin.com/linux/v6.11/source/drivers/bus/ti-sysc.c#L2380
> > If yes, then
> > a) increade the size of the name in the clk subsystem or
> > b) workaround like
> > https://elixir.bootlin.com/linux/v6.11/source/drivers/bus/ti-sysc.c#L353
> >  
> 
> I'll also mention that if one is using DT, then the clkdev tables
> should not be relevant - the lookups of clocks should be done by
> parsing the clocks property in the description of the device.
> 
I played around to ensure I know really what I am doing and what I am
messing around with:
we have in i2c-omap.c:
      
fclk = clk_get(omap->dev, "fck");
just for getting the module clock rate to configure i2c accordingly
That only works if
https://elixir.bootlin.com/linux/v6.11/source/drivers/bus/ti-sysc.c#L2380

is working. Here some clk_get(omap->dev->parent, ...) would also just
work without said line in ti-sysc.c because then dt lookup kicks in.

In the omap3 case, there are several devices using the older hwmod
mechanism and are not converted to ti-sysc yet. Then the clock gets
registered here:
https://elixir.bootlin.com/linux/v6.11/source/arch/arm/mach-omap2/omap_device.c#L116

In the case, a clk_get(omap->dev->parent, ...) in e.g. i2c-omap.c would
fail. No dt lookup can kick in.

The background of this is to ensure to keep soc-specific pm out of the
drivers and do it in a common place.

Regards,
Andreas