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

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Message-ID: <Z77W-fKBUqAALZKJ@hovoldconsulting.com>
Date: Wed, 26 Feb 2025 09:55:21 +0100
From: Johan Hovold <johan@...nel.org>
To: Sibi Sankar <quic_sibis@...cinc.com>
Cc: 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 09:12:23AM +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.

> >  		return;
> >  
> >  	if (!p_addr) {

Johan