Re: [PATCH pci] PCI: don't skip probing entire device if first fn OF node has status = "disabled"

[Vladimir Oltean <vladimir.oltean@nxp.com>]

Hi Rob,

On Fri, Jun 16, 2023 at 11:57:43AM -0600, Rob Herring wrote:
> On Sun, Jun 4, 2023 at 2:55 AM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> >
> 
> Sorry, just now seeing this as I've been out the last month.
> 
> > On Sat, Jun 03, 2023 at 10:35:50AM +0800, Jianmin Lv wrote:
> > > > How about 3. handle of_device_is_available() in the probe function of
> > > > the "loongson, pci-gmac" driver? Would that not work?
> > > >
> > > This way does work only for the specified device. There are other devices,
> > > such as HDA, I2S, etc, which have shared pins. Then we have to add
> > > of_device_is_available() checking to those drivers one by one. And we are
> > > not sure if there are other devices in new generation chips in future. So
> > > I'm afraid that the way you mentioned is not suitable for us.
> 
> If we decided that disabled devices should probe, then that is exactly
> what will have to be done. The restriction (of shared pins) is in the
> devices and is potentially per device, so it makes more sense for the
> device's drivers to handle than the host bridge IMO. (Assuming the
> core doesn't handle a per device property.)
> 
> 
> > Got it, so you have more on-chip PCIe devices than the ones listed in
> > loongson64-2k1000.dtsi, and you don't want to describe them in the
> > device tree just to put status = "disabled" for those devices/functions
> > that you don't want Linux to use - although you could, and it wouldn't
> > be that hard or have unintended side effects.
> >
> > Though you need to admit, in case you had an on-chip multi-function PCIe
> > device like the NXP ENETC, and you wanted Linux to not use function 0,
> > the strategy you're suggesting here that is acceptable for Loongson
> > would not have worked.
> >
> > I believe we need a bit of coordination from PCIe and device tree
> > maintainers, to suggest what would be the encouraged best practices and
> > ways to solve this regression for the ENETC.
> 
> I think we need to define what behavior is correct for 'status =
> "disabled"'. For almost everywhere in DT, it is equivalent to the
> device is not present. A not present device doesn't probe. There are
> unfortunately cases where status got ignored/forgotten and PCI was one
> of those. PCI is a bit different since there are 2 sources of
> information about a device being present. The intent with PCI is DT
> overrides what's discovered. For example, 'vendor-id' overrides what's
> read from the h/w.
> 
> I think we can fix making the status per function simply by making
> 'match_driver' be set based on the status. This would move the check
> later to just before probing. That would not work for a case where
> accessing the config registers is a problem. It doesn't sound like
> that's a problem for Loongson based on the above response, but their
> original solution did prevent that. This change would also mean the
> PCI quirks would run. Perhaps the func0 memory clearing you need could
> be run as a quirk instead?
> 
> Rob

Sorry to return to this thread very late. I had lots of other stuff to
take care of, and somehow *this* breakage had less priority :)

So, first off, there's a confusion regarding the "func0 memory clearing"
that could be run as a quirk instead. It's not memory clearing for fn 0,
but memory clearing for all ENETC functions, regardless or not whether
they have status = "disabled" or not in the device tree.

That being said, I've implemented the workaround below in a quirk as
you've said, and the quirks only get applied for those PCI functions
which don't have status = "disabled" in the device tree. So, as things
stand, it won't work.

Also, the original patch on which we're commenting ("PCI: don't skip
probing entire device if first fn OF node has status = "disabled"") is
needed in any case, because of the other issue: the PCI core thinks that
when fn 0 has status = "disabled", fn 1 .. 6 are also unavailable. False.

From 9c3b88196a7c7e2b010d051c6d48faf36791e220 Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Tue, 20 Jun 2023 16:31:07 +0300
Subject: [PATCH] net: enetc: reimplement RFS/RSS memory clearing as PCI quirk

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 .../net/ethernet/freescale/enetc/enetc_pf.c   | 57 ++++++++++++++-----
 1 file changed, 43 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
index 1416262d4296..b8f6f0799170 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
@@ -1242,18 +1242,6 @@ static int enetc_pf_probe(struct pci_dev *pdev,
 	if (err)
 		goto err_setup_cbdr;

-	err = enetc_init_port_rfs_memory(si);
-	if (err) {
-		dev_err(&pdev->dev, "Failed to initialize RFS memory\n");
-		goto err_init_port_rfs;
-	}
-
-	err = enetc_init_port_rss_memory(si);
-	if (err) {
-		dev_err(&pdev->dev, "Failed to initialize RSS memory\n");
-		goto err_init_port_rss;
-	}
-
 	if (node && !of_device_is_available(node)) {
 		dev_info(&pdev->dev, "device is disabled, skipping\n");
 		err = -ENODEV;
@@ -1339,8 +1327,6 @@ static int enetc_pf_probe(struct pci_dev *pdev,
 	si->ndev = NULL;
 	free_netdev(ndev);
 err_alloc_netdev:
-err_init_port_rss:
-err_init_port_rfs:
 err_device_disabled:
 err_setup_mac_addresses:
 	enetc_teardown_cbdr(&si->cbd_ring);
@@ -1377,6 +1363,49 @@ static void enetc_pf_remove(struct pci_dev *pdev)
 	enetc_pci_remove(pdev);
 }

+static void enetc_fixup_clear_rss_rfs(struct pci_dev *pdev)
+{
+	struct enetc_si *si;
+	struct enetc_pf *pf;
+	int err;
+
+	err = enetc_pci_probe(pdev, KBUILD_MODNAME, sizeof(*pf));
+	if (err)
+		goto out;
+
+	si = pci_get_drvdata(pdev);
+	if (!si->hw.port || !si->hw.global) {
+		err = -ENODEV;
+		goto out_pci_remove;
+	}
+
+	err = enetc_setup_cbdr(&pdev->dev, &si->hw, ENETC_CBDR_DEFAULT_SIZE,
+			       &si->cbd_ring);
+	if (err)
+		goto out_pci_remove;
+
+	err = enetc_init_port_rfs_memory(si);
+	if (err)
+		goto out_teardown_cbdr;
+
+	err = enetc_init_port_rss_memory(si);
+	if (err)
+		goto out_teardown_cbdr;
+
+out_teardown_cbdr:
+	enetc_teardown_cbdr(&si->cbd_ring);
+out_pci_remove:
+	enetc_pci_remove(pdev);
+out:
+	if (err) {
+		dev_err(&pdev->dev,
+			"Failed to apply PCI fixup for clearing RFS/RSS memories: %pe\n",
+			ERR_PTR(err));
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_FREESCALE, ENETC_DEV_ID_PF,
+			enetc_fixup_clear_rss_rfs);
+
 static const struct pci_device_id enetc_pf_id_table[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_FREESCALE, ENETC_DEV_ID_PF) },
 	{ 0, } /* End of table. */
--
2.34.1