[PATCH V1] firmware: arm_scmi: clock: support clock denied flags

[Peng Fan]

> Subject: Re: [PATCH V1] firmware: arm_scmi: clock: support clock denied
> flags
> 
> On Tue, Oct 31, 2023 at 08:27:34PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan at nxp.com>
> >
> > The firmware may export flags to indicate whether the clock is allowed
> > to set rate, set parent, enable/disable from the Agent.
> >
> > If Agent is not allowed to enable/disable, directly return success.
> 
> ... even though, this success on deny built-in policy could be
> controversial..
Yeah. 

.Have you tried the different approach of not registerig the
> enable/prepare callbacks in clk-scmi instead ?

Not yet, I could give a look. But not have much time
in the following week.


> From the Clk framework code it seems could be handled gracefully.
> (I have not tried though...)

If there is no enable/disable/prepare/unprepared hooks, the enable
counter or prepare counter would be used.

Thanks,
Peng.
> 
> Thanks,
> Cristian
> 
> > If Agent is not allowed to set rate/parent, directly return -EACCES to
> > avoid SCMI RPC calls.
> >
> > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > ---
> >
> > V1:
> >  drop the changes in clock.c, add an attribute entry in clock info
> > which  may be easy for extending new flag.
> >
> >  SPEC still not have such support, this is for discussion
> >
> >  drivers/firmware/arm_scmi/clock.c | 19 +++++++++++++++++++
> >  include/linux/scmi_protocol.h     |  1 +
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/drivers/firmware/arm_scmi/clock.c
> > b/drivers/firmware/arm_scmi/clock.c
> > index 42b81c181d68..fad4329a21fc 100644
> > --- a/drivers/firmware/arm_scmi/clock.c
> > +++ b/drivers/firmware/arm_scmi/clock.c
> > @@ -46,6 +46,9 @@ struct scmi_msg_resp_clock_attributes {
> >  #define SUPPORTS_RATE_CHANGE_REQUESTED_NOTIF(x)	((x) &
> BIT(30))
> >  #define SUPPORTS_EXTENDED_NAMES(x)		((x) & BIT(29))
> >  #define SUPPORTS_PARENT_CLOCK(x)		((x) & BIT(28))
> > +#define SCMI_CLOCK_SET_ENABLE_DENIED		BIT(15)
> > +#define SCMI_CLOCK_SET_RATE_DENIED		BIT(14)
> > +#define SCMI_CLOCK_SET_PARENT_DENIED		BIT(13)
> >  	u8 name[SCMI_SHORT_NAME_MAX_SIZE];
> >  	__le32 clock_enable_latency;
> >  };
> > @@ -307,6 +310,7 @@ static int scmi_clock_attributes_get(const struct
> scmi_protocol_handle *ph,
> >  		if (PROTOCOL_REV_MAJOR(version) >= 0x2)
> >  			latency = le32_to_cpu(attr->clock_enable_latency);
> >  		clk->enable_latency = latency ? : U32_MAX;
> > +		clk->attributes = attributes;
> >  	}
> >
> >  	ph->xops->xfer_put(ph, t);
> > @@ -499,6 +503,10 @@ static int scmi_clock_rate_set(const struct
> scmi_protocol_handle *ph,
> >  	struct scmi_xfer *t;
> >  	struct scmi_clock_set_rate *cfg;
> >  	struct clock_info *ci = ph->get_priv(ph);
> > +	struct scmi_clock_info *clk = ci->clk + clk_id;
> > +
> > +	if (clk->attributes & SCMI_CLOCK_SET_RATE_DENIED)
> > +		return -EACCES;
> >
> >  	ret = ph->xops->xfer_get_init(ph, CLOCK_RATE_SET, sizeof(*cfg), 0,
> &t);
> >  	if (ret)
> > @@ -585,6 +593,9 @@ scmi_clock_set_parent(const struct
> scmi_protocol_handle *ph, u32 clk_id,
> >  	if (parent_id >= clk->num_parents)
> >  		return -EINVAL;
> >
> > +	if (clk->attributes & SCMI_CLOCK_SET_PARENT_DENIED)
> > +		return -EACCES;
> > +
> >  	ret = ph->xops->xfer_get_init(ph, CLOCK_PARENT_SET,
> >  				      sizeof(*cfg), 0, &t);
> >  	if (ret)
> > @@ -668,6 +679,10 @@ static int scmi_clock_enable(const struct
> scmi_protocol_handle *ph, u32 clk_id,
> >  			     bool atomic)
> >  {
> >  	struct clock_info *ci = ph->get_priv(ph);
> > +	struct scmi_clock_info *clk = ci->clk + clk_id;
> > +
> > +	if (clk->attributes & SCMI_CLOCK_SET_ENABLE_DENIED)
> > +		return 0;
> >
> >  	return ci->clock_config_set(ph, clk_id, CLK_STATE_ENABLE,
> >  				    NULL_OEM_TYPE, 0, atomic);
> > @@ -677,6 +692,10 @@ static int scmi_clock_disable(const struct
> scmi_protocol_handle *ph, u32 clk_id,
> >  			      bool atomic)
> >  {
> >  	struct clock_info *ci = ph->get_priv(ph);
> > +	struct scmi_clock_info *clk = ci->clk + clk_id;
> > +
> > +	if (clk->attributes & SCMI_CLOCK_SET_ENABLE_DENIED)
> > +		return 0;
> >
> >  	return ci->clock_config_set(ph, clk_id, CLK_STATE_DISABLE,
> >  				    NULL_OEM_TYPE, 0, atomic);
> > diff --git a/include/linux/scmi_protocol.h
> > b/include/linux/scmi_protocol.h index f2f05fb42d28..ddf5363c8cfd
> > 100644
> > --- a/include/linux/scmi_protocol.h
> > +++ b/include/linux/scmi_protocol.h
> > @@ -58,6 +58,7 @@ struct scmi_clock_info {
> >  			u64 step_size;
> >  		} range;
> >  	};
> > +	u32 attributes;
> >  	int num_parents;
> >  	u32 *parents;
> >  };
> > --
> > 2.37.1
> >