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

Vladimir Oltean
2023-08-03T11:34:33Z

On Thu, Aug 03, 2023 at 01:39:55PM +0300, Vladimir Oltean wrote:
> 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
>

Ah, sorry, I completely missed your comment about match_driver.
So I've added this extra patch and both issues are solved. The fixup
runs for all functions (thus I see no AER errors), and functions 1 .. 6
continue to probe even when function 0 has status = "disabled".

From 3528d4a48cb37dce8d1d83d2fbb465f21a32adcd Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Thu, 3 Aug 2023 14:31:27 +0300
Subject: [PATCH] PCI: move OF status = "disabled" detection to
dev->match_driver

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
drivers/pci/bus.c | 4 +++-
drivers/pci/of.c | 5 -----
2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 5bc81cc0a2de..46b252bbe500 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -11,6 +11,7 @@
#include <linux/pci.h>
#include <linux/errno.h>
#include <linux/ioport.h>
+#include <linux/of.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>

@@ -332,6 +333,7 @@ void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
*/
void pci_bus_add_device(struct pci_dev *dev)
{
+ struct device_node *dn = dev->dev.of_node;
int retval;

/*
@@ -344,7 +346,7 @@ void pci_bus_add_device(struct pci_dev *dev)
pci_proc_attach_device(dev);
pci_bridge_d3_update(dev);

- dev->match_driver = true;
+ dev->match_driver = !dn || of_device_is_available(dn);
retval = device_attach(&dev->dev);
if (retval < 0 && retval != -EPROBE_DEFER)
pci_warn(dev, "device attach failed (%d)\n", retval);
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index e51219f9f523..3c158b17dcb5 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -34,11 +34,6 @@ int pci_set_of_node(struct pci_dev *dev)
if (!node)
return 0;

- if (!of_device_is_available(node)) {
- of_node_put(node);
- return -ENODEV;
- }
-
device_set_node(&dev->dev, of_fwnode_handle(node));
return 0;
}
--
2.34.1