RE: [PATCH] clk: imx: introduce imx_clk_hw_critical

[Aisheng Dong <aisheng.dong@nxp.com>]

> From: Peng Fan <peng.fan@nxp.com>
> Sent: Friday, April 24, 2020 9:08 AM
> 
> > Subject: RE: [PATCH] clk: imx: introduce imx_clk_hw_critical
> >
> > > From: Peng Fan <peng.fan@nxp.com>
> > > Sent: Thursday, April 23, 2020 6:54 PM
> > >
> > > > Subject: RE: [PATCH] clk: imx: introduce imx_clk_hw_critical
> > > >
> > > > > From: Peng Fan <peng.fan@nxp.com>
> > > > > 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@nxp.com>
> > > > > ---
> > > > >  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.

> 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#L4891

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