linux-kernel - Re: [RFC] drm/msm/dp: Allow attaching a drm

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Message-ID: <ZG3d0pW1qN55lWTZ@kuha.fi.intel.com>
Date:   Wed, 24 May 2023 12:50:10 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Prashant Malani <pmalani@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Vara Reddy <varar@...eaurora.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Benson Leung <bleung@...omium.org>
Subject: Re: [RFC] drm/msm/dp: Allow attaching a drm_panel

On Mon, May 22, 2023 at 02:53:48PM -0700, Bjorn Andersson wrote:
> On Mon, May 22, 2023 at 03:51:01PM -0500, Bjorn Andersson wrote:
> > On Fri, Oct 08, 2021 at 03:38:21PM +0300, Heikki Krogerus wrote:
> > > Hi,
> > > 
> > > On Thu, Oct 07, 2021 at 09:15:12AM -0700, Bjorn Andersson wrote:
> > > > The one thing that I still don't understand though is, if the typec_mux
> > > > is used by the typec controller to inform _the_ mux about the function
> > > > to be used, what's up with the complexity in typec_mux_match()? This is
> > > > what lead me to believe that typec_mux was enabling/disabling individual
> > > > altmodes, rather just flipping the physical switch at the bottom.
> > > 
> > > Ah, typec_mux_match() is a mess. I'm sorry about that. I think most of
> > > the code in that function is not used by anybody. If I remember
> > > correctly, all that complexity is attempting to solve some
> > > hypothetical corner case(s). Probable a case where we have multiple
> > > muxes per port to deal with.
> > > 
> > > I think it would probable be best to clean the function to the bare
> > > minimum by keeping only the parts that are actually used today
> > > (attached).
> > > 
> > 
> > Sorry for not replying to this in a timely manner Heikki. I've been
> > ignoring this issue for a long time now, just adding "svid" to our dts
> > files. But, this obviously shows up in DT validation - and I'd prefer
> > not defining these properties as valid.
> > 
> > The attached patch works as expected.
> > 
> 
> Sorry, I must have failed at applying the patch - it doesn't work...
> 
> > Could you please spin this as a proper patch, so we can get it merged?
> > 
> > Regards,
> > Bjorn
> > 
> > > thanks,
> > > 
> > > -- 
> > > heikki
> > 
> > > diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
> > > index c8340de0ed495..44f168c9bd9bf 100644
> > > --- a/drivers/usb/typec/mux.c
> > > +++ b/drivers/usb/typec/mux.c
> > > @@ -193,56 +193,15 @@ static int mux_fwnode_match(struct device *dev, const void *fwnode)
> > >  static void *typec_mux_match(struct fwnode_handle *fwnode, const char *id,
> > >  			     void *data)
> > >  {
> > > -	const struct typec_altmode_desc *desc = data;
> > >  	struct device *dev;
> > > -	bool match;
> > > -	int nval;
> > > -	u16 *val;
> > > -	int ret;
> > > -	int i;
> > >  
> > >  	/*
> > > -	 * Check has the identifier already been "consumed". If it
> > > -	 * has, no need to do any extra connection identification.
> > > +	 * The connection identifier will be needed with device graph (OF graph).
> > > +	 * Device graph is not supported by this code yet, so bailing out.
> > >  	 */
> > > -	match = !id;
> > > -	if (match)
> > > -		goto find_mux;
> > > -
> > > -	/* Accessory Mode muxes */
> > > -	if (!desc) {
> > > -		match = fwnode_property_present(fwnode, "accessory");
> > > -		if (match)
> > > -			goto find_mux;
> > > -		return NULL;
> > > -	}
> > > -
> > > -	/* Alternate Mode muxes */
> > > -	nval = fwnode_property_count_u16(fwnode, "svid");
> > > -	if (nval <= 0)
> > > -		return NULL;
> > > -
> > > -	val = kcalloc(nval, sizeof(*val), GFP_KERNEL);
> > > -	if (!val)
> > > -		return ERR_PTR(-ENOMEM);
> > > -
> > > -	ret = fwnode_property_read_u16_array(fwnode, "svid", val, nval);
> > > -	if (ret < 0) {
> > > -		kfree(val);
> > > -		return ERR_PTR(ret);
> > > -	}
> > > -
> > > -	for (i = 0; i < nval; i++) {
> > > -		match = val[i] == desc->svid;
> > > -		if (match) {
> > > -			kfree(val);
> > > -			goto find_mux;
> > > -		}
> > > -	}
> > > -	kfree(val);
> > > -	return NULL;
> > > +	if (id)
> 
> We pass id as "mode-switch", so this will never be NULL. But we also only
> want to consider endpoints with "mode-switch", otherwise we'll fail if
> any of the referred endpoints is not implementing a typec_mux...
> 
> So this needs the same snippet we find in typec_switch_match():
> 
> 	/*
> 	 * Device graph (OF graph) does not give any means to identify the
> 	 * device type or the device class of the remote port parent that @fwnode
> 	 * represents, so in order to identify the type or the class of @fwnode
> 	 * an additional device property is needed. With typec switches the
> 	 * property is named "orientation-switch" (@id). The value of the device
> 	 * property is ignored.
> 	 */
> 	if (id && !fwnode_property_present(fwnode, id))
> 	        return NULL;
> 
> With that, this works as expected!

Okay. I'll change that and send the patch out.

thanks,

-- 
heikki