Message-ID: <aAd-lIzIGxzxfWXC@pluto>
Date: Tue, 22 Apr 2025 12:33:40 +0100
From: Cristian Marussi <cristian.marussi@....com>
To: Johan Hovold <johan@...nel.org>
Cc: Sudeep Holla <sudeep.holla@....com>,
	Cristian Marussi <cristian.marussi@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	arm-scmi@...r.kernel.org, james.quinlan@...adcom.com,
	f.fainelli@...il.com, vincent.guittot@...aro.org,
	peng.fan@....nxp.com, michal.simek@....com, quic_sibis@...cinc.com,
	dan.carpenter@...aro.org, maz@...nel.org
Subject: Re: [PATCH 2/4] firmware: arm_scmi: Add Quirks framework

On Tue, Apr 22, 2025 at 12:41:47PM +0200, Johan Hovold wrote:
> On Thu, Apr 17, 2025 at 03:41:56PM +0100, Sudeep Holla wrote:
> > On Thu, Apr 17, 2025 at 12:10:25PM +0100, Cristian Marussi wrote:
> > > On Thu, Apr 17, 2025 at 10:44:24AM +0200, Johan Hovold wrote:
> > > > On Wed, Apr 16, 2025 at 05:37:13PM +0100, Cristian Marussi wrote:
> > > > > On Wed, Apr 16, 2025 at 06:00:37PM +0200, Johan Hovold wrote:
> > > > > > On Tue, Apr 15, 2025 at 03:29:31PM +0100, Cristian Marussi wrote:
> > > > 
> > > > > > > +static void scmi_enable_matching_quirks(struct scmi_info *info)
> > > > > > > +{
> > > > > > > +	struct scmi_revision_info *rev = &info->version;
> > > > > > > +	const char *compatible = NULL;
> > > > > > > +	struct device_node *root;
> > > > > > > +
> > > > > > > +	root = of_find_node_by_path("/");
> > > > > > > +	if (root) {
> > > > > > > +		of_property_read_string(root, "compatible", &compatible);
> > > > > > 
> > > > > > Looks like you still only allow matching on the most specific compatible
> > > > > > string.
> > > > > > 
> > > > > > As we discussed in the RFC thread, this will result in one quirk entry
> > > > > > for each machine in a SoC family in case the issue is not machine
> > > > > > specific.
> >

Hi,

a quick one that I am away from the keyboard currently ...
 
> > Agreed, but we can predict that. You can infer just from the current state
> > of affairs. Today all machines based on soc X may need the quirk but the
> > firmware may vary across machines with same SoC.
> 
> Sure, I was just highlighting this limitation in the current
> implementation...
> 
> > > > I was referring to the need to match on other compatible strings than
> > > > the most specific one. For the ThinkPad T14s the strings are:
> > > > 
> > > > 	"lenovo,thinkpad-t14s-lcd", "lenovo,thinkpad-t14s",
> > > > 	"qcom,x1e78100", "qcom,x1e80100"
> > > > 
> > > > Here you most certainly would not want to match on
> > > > "lenovo,thinkpad-t14s-lcd" but rather on "lenovo,thinkpad-t14s" or one
> > > > of the SoC compatibles.
> 
> ...and the fact that even if you want to avoid matching on SoC
> compatible, the current implementation seems to be too limited to allow
> matching on machine compatibles generally (i.e. given that there may be
> variants of a particular machine).
> 
> We may not even need this for the FC quirk, this was just a general
> observation.
> 
> > > > of_machine_is_compatible() can be used to match on any compatible
> > > > string, but not sure if that fits with your current implementation.
> > > > 
> > 
> > I was thinking about the same when I looked at the code. Using it is
> > more elegant IMO.
> 
> It would be more flexible, even if you never intend to accept any quirks
> that matches for an entire SoC.
> 


I already have a V2 under test that will define a quirk using a
__VA_ARGS__ so that you can specify a variable number of compats to
match against the platform running using of_machine_compatible_match()

+/*
+ * Define a quirk by name (_qn) and provide the matching tokens where:
+ *
+ *  _ven : SCMI Vendor ID string, NULL means any.
+ *  _sub : SCMI SubVendor ID string, NULL means any.
+ *  _impl : SCMI Implementation Version string, NULL means any.
+ *          This version string can express ranges using the following
+ *          syntax:
+ *
+ *                     NULL            [0, 0xFFFFFFFF]
+ *                     "X"             [X, X]
+ *                     "X-"            [X, 0xFFFFFFFF]
+ *                     "-X"            [0, X]
+ *                     "X-Y"           [X, Y]
+ *
+ *          where <v> in [MIN, MAX] means:
+ *
+ *             MIN <= <v> <= MAX  && MIN <= MAX
+ *
+ *  _comps : NULL terminated array of compatible strings.
+ *          An empty array means any.
+ *
+ *  This implicitly define also a properly named global static-key that
+ *  will be used to dynamically enable the quirk at initialization time.
+ *
+ *  Note that it is possible to associate multiple quirks to the same
+ *  matching pattern, if your firmware quality is really astounding :P
+ */
+#define DEFINE_SCMI_QUIRK(_qn, _ven, _sub, _impl, ...)                 \

I will post V2 soon.

> > > ...moreover this kind of carpet-quirking that hides the issue on any possible
> > > fw version gives ZERO incentives to the aforementioned vendor to fix its
> > > firmware...(or it fw-release process)...
> 
> If a vendor truly only cares about some other OS then perhaps this
> argument isn't that strong and we'll just increase our own maintenance
> burden.
> 

indeed.

> > > Indeed, cross posting from your other mail thread, as of now we cannot
> > > even be sure if the Vendor has somehow already updated the SCMI-related
> > > firmware NEITHER we can be sure about this in the future since it has not
> > > even confirmed how they are (or they will) be handling the Impl_Version field...
> > > 
> > > Having said that, I would add that in this specific case (FC quirk) since the
> > > only way to make use of all of this SCMI stuff from the MicroZoft/ACPI world
> > > is having working FCs and, since it's clear that our lovely vendor wont
> > > certainly break this other lovely OS way of working with SCMI, MAYBE it could
> > > be safe to just apply the quirk to this Vendor forever no matter what the
> > > platform or FW version will be in the future...(so not using compats at all)
> 
> My understanding is that the version has been bumped now albeit for
> other reasons than fixing this particular bug. And since enabling FC for
> these messages should be safe we will probably be able to match on
> vendor/impl_version here.

So what is your latest Firmware version read ? no more 0x20000

[    0.116746] arm-scmi arm-scmi.0.auto: SCMI Protocol ?? 'Qualcom:' Firmware version ???????

> 
> Sibi is looking into this and should be able to provide an answer
> shortly.
> 

Good.

Thanks,
Cristian

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