linux-kernel - Re: [RFC V6 2/2] firmware: arm_scmi: Add quirk to bypass SCP fw bug

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Message-ID: <759226e1-05aa-4ca2-b2f5-7f1a84dc427f@stanley.mountain>
Date: Wed, 26 Feb 2025 12:31:27 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Sibi Sankar <quic_sibis@...cinc.com>, sudeep.holla@....com,
	cristian.marussi@....com, dmitry.baryshkov@...aro.org,
	maz@...nel.org, linux-kernel@...r.kernel.org,
	arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org, konradybcio@...nel.org
Subject: Re: [RFC V6 2/2] firmware: arm_scmi: Add quirk to bypass SCP fw bug

On Wed, Feb 26, 2025 at 09:55:21AM +0100, Johan Hovold wrote:
> On Wed, Feb 26, 2025 at 09:12:23AM +0100, Johan Hovold wrote:
> > On Wed, Feb 26, 2025 at 08:13:38AM +0530, Sibi Sankar wrote:
> 
> > >  scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
> > >  			     u8 describe_id, u32 message_id, u32 valid_size,
> > >  			     u32 domain, void __iomem **p_addr,
> > > -			     struct scmi_fc_db_info **p_db, u32 *rate_limit)
> > > +			     struct scmi_fc_db_info **p_db, u32 *rate_limit,
> > > +			     bool skip_check)
> > 
> > This does not look like it will scale.
> 
> After taking a closer look, perhaps it needs to be done along these
> lines.
> 
> But calling the parameter 'force' or similar as Dan suggested should
> make it more readable.
> 
> > 
> > >  {
> > >  	int ret;
> > >  	u32 flags;
> > > @@ -1919,7 +1920,7 @@ scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
> > >  
> > >  	/* Check if the MSG_ID supports fastchannel */
> > >  	ret = scmi_protocol_msg_check(ph, message_id, &attributes);
> > > -	if (!ret && !MSG_SUPPORTS_FASTCHANNEL(attributes))
> > > +	if (!ret && !MSG_SUPPORTS_FASTCHANNEL(attributes) && !skip_check)
> > 
> > Why can't you just make sure that the bit is set in attributes as I
> > suggested? That seems like it should allow for a minimal implementation
> > of this.
> 
> My idea here was that you could come up with some way of abstracting
> this so that you did not have to update every call site. Not sure how
> feasible that is.
> 

I'm having a hard time finding your email.

Why does the scmi_proto_helpers_ops struct even exist?  We could just
call all these functions directly.  Do we have plans to actually create
different implementations?

If we got rid of the scmi_proto_helpers_ops struct then we could just
rename scmi_common_fastchannel_init() to __scmi_common_fastchannel_init()
and create a default wrapper around it and a _forced() wrapper.

Some other potentially stupid ideas in the spirit of brainstorming are
that we could add a quirks parameter which takes a flag instead of a
bool.  Or we could add a quirks flag to the scmi_protocol_handle struct.

regards,
dan carpenter