RE: [PATCH] clk: imx: introduce imx_clk_hw_critical

[Peng Fan]

> Subject: RE: [PATCH] clk: imx: introduce imx_clk_hw_critical
> 
> > From: Peng Fan <peng.fan@xxxxxxx>
> > Sent: Friday, April 24, 2020 9:08 AM
> >
> > > Subject: RE: [PATCH] clk: imx: introduce imx_clk_hw_critical
> > >
> > > > From: Peng Fan <peng.fan@xxxxxxx>
> > > > Sent: Thursday, April 23, 2020 6:54 PM
> > > >
> > > > > Subject: RE: [PATCH] clk: imx: introduce imx_clk_hw_critical
> > > > >
> > > > > > From: Peng Fan <peng.fan@xxxxxxx>
> > > > > > Sent: Thursday, April 23, 2020 2:52 PM
> > > > > >
> > > > > > To i.MX8M SoC, there is an case is when running dual OSes with
> > > > > > hypervisor, the clk of the hardware that passthrough to the
> > > > > > 2nd OS needs to be setup by 1st Linux OS.
> > > > > > So detect clock-critical from ccm node and enable the clocks
> > > > > > to let the 2nd OS could use the hardware without touch CCM
> module.
> > > > > >
> > > > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > > > > > ---
> > > > > >  drivers/clk/imx/clk.c | 19 +++++++++++++++++++
> > > > > > drivers/clk/imx/clk.h
> > > > > > |  1
> > > > > > +
> > > > > >  2 files changed, 20 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> > > > > > index
> > > > > > 87ab8db3d282..ec7d422540c1 100644
> > > > > > --- a/drivers/clk/imx/clk.c
> > > > > > +++ b/drivers/clk/imx/clk.c
> > > > > > @@ -177,3 +177,22 @@ static int __init imx_clk_disable_uart(void)
> > > > > >  	return 0;
> > > > > >  }
> > > > > >  late_initcall_sync(imx_clk_disable_uart);
> > > > > > +
> > > > > > +int imx_clk_hw_critical(struct device_node *np, struct clk_hw
> > > > > > +* const
> > > > > > +hws[]) {
> > > > > > +	struct property *prop;
> > > > > > +	const __be32 *cur;
> > > > > > +	u32 idx;
> > > > > > +	int ret;
> > > > > > +
> > > > > > +	if (!np || !hws)
> > > > > > +		return -EINVAL;
> > > > > > +
> > > > > > +	of_property_for_each_u32(np, "clock-critical", prop, cur,
> > > > > > +idx) {
> > > > >
> > > > > Is there a binding for it already?
> > > >
> > > > I think clock-critical is a common bindings? See of_clk_detect_critical.
> > > > Please review whether this approach is acceptable, if do need
> > > > bindings, I could add that in v2.
> > > >
> > >
> > > I'm ok if it's a common binding already supported by current clk
> framework.
> > > But it seems to be more like a common clk feature rather than
> > > platform feature.
> >
> > Here is to use it for dual Linux case running on i.MX plaforms.
> > It is to replace the init-on-array property in downstream kernel.
> >
> > The recommended critical clock is using CLK_IS_CRITICAL flag in clk
> > driver, not use clock-critical property.
> >
> 
> Clock-critical property seems DT usage of CLK_IS_CRITICAL flag and pure
> platform independent.
> So I wonder if this feature could be added into of_clk_add_hw_provider.

After check, of_clk_add_hw_provider takes node pointer and a function pointer
as parameter, however clock-critical needs clk index and the clk_hw array
pointer. It needs more changes to common code that I would not like
to do.

Thanks,
Peng.

> 
> > But here, we could not use CLK_IS_CRITICAL, because when support dual
> > OSes, it is not flexible, and it will affect non hypervisor case.
> >
> 
> A bit confuing because you said the critical-clock property will only be used by
> Hypervisor dts, then how to affect non hypervisor cases?
> 
> > > Also a bit strange that why I did not find the binding doc in latest kernel.
> > > Maybe Stephen could comment more.
> >
> > It is used here.
> > https://elixir.bootlin.com/linux/v5.7-rc2/source/drivers/clk/clk.c#L48
> > 91
> 
> Yes, I also saw it, but didn't find binding doc.
> 
> Regards
> Aisheng
> 
> >
> > >
> > > BTW, if using this for dual OSes case, will those critical clocks
> > > affect the normal users that not booting the second OS?
> >
> > No. dual os using x-root.dts, not x.dts. critical-clock will be push in
> x-root.dts.
> >
> > Thanks,
> > Peng.
> >
> > >
> > > Regards
> > > Aisheng
> > >
> > > > Thanks,
> > > > Peng.
> > > >
> > > > >
> > > > > Regards
> > > > > Aisheng
> > > > >
> > > > > > +		ret = clk_prepare_enable(hws[idx]->clk);
> > > > > > +		if (ret)
> > > > > > +			return ret;
> > > > > > +	}
> > > > > > +
> > > > > > +	return 0;
> > > > > > +}
> > > > > > diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
> > > > > > index d4ea1609bcb7..701d7440f98c 100644
> > > > > > --- a/drivers/clk/imx/clk.h
> > > > > > +++ b/drivers/clk/imx/clk.h
> > > > > > @@ -9,6 +9,7 @@ extern spinlock_t imx_ccm_lock;
> > > > > >
> > > > > >  void imx_check_clocks(struct clk *clks[], unsigned int
> > > > > > count); void imx_check_clk_hws(struct clk_hw *clks[], unsigned
> > > > > > int count);
> > > > > > +int imx_clk_hw_critical(struct device_node *np, struct clk_hw
> > > > > > +* const hws[]);
> > > > > >  void imx_register_uart_clocks(struct clk ** const clks[]);
> > > > > > void imx_mmdc_mask_handshake(void __iomem *ccm_base,
> unsigned
> > > > > > int
> > > chn);
> > > > > > void imx_unregister_clocks(struct clk *clks[], unsigned int
> > > > > > count);
> > > > > > --
> > > > > > 2.16.4