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PCI: Restore original INTX_DISABLE bit by pcim_intx()

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pcim_intx() tries to restore the INTx bit at removal via devres, but there
is a chance that it restores a wrong value.

Because the value to be restored is blindly assumed to be the negative of
the enable argument, when a driver calls pcim_intx() unnecessarily for the
already enabled state, it'll restore to the disabled state in turn.  That
is, the function assumes the case like:

  // INTx == 1
  pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> correct

but it might be like the following, too:

  // INTx == 0
  pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> wrong

Also, when a driver calls pcim_intx() multiple times with different enable
argument values, the last one will win no matter what value it is.  This
can lead to inconsistency, e.g.

  // INTx == 1
  pcim_intx(pdev, 0); // OK
  ...
  pcim_intx(pdev, 1); // now old INTx wrongly assumed to be 0

This patch addresses those inconsistencies by saving the original INTx
state at the first pcim_intx() call.  For that, get_or_create_intx_devres()
is folded into pcim_intx() caller side; it allows us to simply check the
already allocated devres and record the original INTx along with the
devres_alloc() call.

Link: https://lore.kernel.org/r/20241031134300.10296-1-tiwai@suse.de
Fixes: 25216afc9d ("PCI: Add managed pcim_intx()")
Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Philipp Stanner <pstanner@redhat.com>
Cc: stable@vger.kernel.org	# v6.11+
This commit is contained in:
Takashi Iwai 2024-10-31 14:42:56 +01:00 • committed by Bjorn Helgaas
parent 647d69605c
commit d555ed45a5
1 changed files with 19 additions and 15 deletions
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34
drivers/pci/devres.c
View file

@ -419,19 +419,12 @@ static void pcim_intx_restore(struct device *dev, void *data)
pci_intx(pdev, res->orig_intx);
}
static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
static void save_orig_intx(struct pci_dev *pdev, struct pcim_intx_devres *res)
{
struct pcim_intx_devres *res;
u16 pci_command;
res = devres_find(dev, pcim_intx_restore, NULL, NULL);
if (res)
return res;
res = devres_alloc(pcim_intx_restore, sizeof(*res), GFP_KERNEL);
if (res)
devres_add(dev, res);
return res;
pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
res->orig_intx = !(pci_command & PCI_COMMAND_INTX_DISABLE);
}
/**
@ -447,12 +440,23 @@ static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
int pcim_intx(struct pci_dev *pdev, int enable)
{
struct pcim_intx_devres *res;
struct device *dev = &pdev->dev;
res = get_or_create_intx_devres(&pdev->dev);
if (!res)
return -ENOMEM;
/*
* pcim_intx() must only restore the INTx value that existed before the
* driver was loaded, i.e., before it called pcim_intx() for the
* first time.
*/
res = devres_find(dev, pcim_intx_restore, NULL, NULL);
if (!res) {
res = devres_alloc(pcim_intx_restore, sizeof(*res), GFP_KERNEL);
if (!res)
return -ENOMEM;
save_orig_intx(pdev, res);
devres_add(dev, res);
}
res->orig_intx = !enable;
pci_intx(pdev, enable);
return 0;