Re: [PATCH v2 1/7] PCI: Keep the ACS capability offset in device

From: Rajat Jain <rajatja@google.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Joerg Roedel <joro@8bytes.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <lenb@kernel.org>,
	"open list:AMD IOMMU (AMD-VI)" <iommu@lists.linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
	Raj Ashok <ashok.raj@intel.com>,
	"Krishnakumar,
	Lalithambika" <lalithambika.krishnakumar@intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Prashant Malani <pmalani@google.com>,
	Benson Leung <bleung@google.com>, Todd Broch <tbroch@google.com>,
	Alex Levin <levinale@google.com>,
	Mattias Nissler <mnissler@google.com>,
	Rajat Jain <rajatxjain@gmail.com>,
	Bernie Keany <bernie.keany@intel.com>,
	Aaron Durbin <adurbin@google.com>,
	Diego Rivas <diegorivas@google.com>,
	Duncan Laurie <dlaurie@google.com>,
	Furquan Shaikh <furquan@google.com>,
	Jesse Barnes <jsbarnes@google.com>,
	Christian Kellner <christian@kellner.me>,
	Alex Williamson <alex.williamson@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Oliver O'Halloran" <oohall@gmail.com>,
	Saravana Kannan <saravanak@google.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>
Subject: Re: [PATCH v2 1/7] PCI: Keep the ACS capability offset in device
Date: Mon, 6 Jul 2020 15:16:42 -0700	[thread overview]
Message-ID: <CACK8Z6GtOH4o6J17YXnesf0VvQSQRTCR011RRD2U7gkrwA8ziQ@mail.gmail.com> (raw)
In-Reply-To: <20200706155815.GA119406@bjorn-Precision-5520>

Hi Bjorn,

Thanks for taking a look.

On Mon, Jul 6, 2020 at 8:58 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Mon, Jun 29, 2020 at 09:49:37PM -0700, Rajat Jain wrote:
> > Currently this is being looked up at a number of places. Read and store it
> > once at bootup so that it can be used by all later.
>
> Write the commit log so it is complete even without the subject.
> Right now, you have to read the subject to know what "this" refers to.
>
> The subject is like the title; the log is like the body of an article.
> The title isn't *part* of the article, so the article has to make
> sense all by itself.

Fixed.

>
> > +static void pci_enable_acs(struct pci_dev *dev);
>
> I don't think we need this forward declaration, do we?

We need it unless we move its definition further up in the file:

drivers/pci/pci.c: In function ‘pci_restore_state’:
drivers/pci/pci.c:1551:2: error: implicit declaration of function
‘pci_enable_acs’; did you mean ‘pci_enable_ats’?
[-Werror=implicit-function-declaration]
 1551 |  pci_enable_acs(dev);

Do you want me to move it up in the file so that we do not need the
forward declaration?

>
> > @@ -4653,7 +4653,7 @@ static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags)
> >       if (!pci_quirk_intel_spt_pch_acs_match(dev))
> >               return -ENOTTY;
> >
> > -     pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
> > +     pos = dev->acs_cap;
>
> I assume you verified that all these quirks are FINAL quirks, since
> pci_init_capabilities() is called after HEADER quirks.  I'll
> double-check before applying this.

None of these quirks are applied via DECLARE_PCI_FIXUP_*(). All these
quirks are called (directly or indirectly) from either
pci_enable_acs() or pci_acs_enabled(),

EXCEPT

pci_idt_bus_quirk(). That one is called from
pci_bus_read_dev_vendor_id() which should be called only after the
parent bridge has been added and setup correctly.

So it looks all good to me.

Thanks,

Rajat

>
> Bjorn