linux-kernel - [PATCH] PCI: Restore the original INTX_DISABLE bit by pcim

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Message-ID: <20241024155539.19416-1-tiwai@suse.de>
Date: Thu, 24 Oct 2024 17:55:35 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Philipp Stanner <pstanner@...hat.com>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] PCI: Restore the original INTX_DISABLE bit by pcim_intx()

pcim_intx() tries to restore the INTX_DISABLE 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.  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 patch addresses those inconsistencies by saving the original
INTX_DISABLE state at the first devres_alloc(); this assures that the
original state is restored properly, and the later pcim_intx() calls
won't overwrite res->orig_intx any longer.

Fixes: 25216afc9db5 ("PCI: Add managed pcim_intx()")
Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/pci/devres.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
index b133967faef8..aed3c9a355cb 100644
--- a/drivers/pci/devres.c
+++ b/drivers/pci/devres.c
@@ -438,8 +438,17 @@ static void pcim_intx_restore(struct device *dev, void *data)
 	__pcim_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)
 {
+	u16 pci_command;
+
+	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
+	res->orig_intx = !(pci_command & PCI_COMMAND_INTX_DISABLE);
+}
+
+static struct pcim_intx_devres *get_or_create_intx_devres(struct pci_dev *pdev)
+{
+	struct device *dev = &pdev->dev;
 	struct pcim_intx_devres *res;
 
 	res = devres_find(dev, pcim_intx_restore, NULL, NULL);
@@ -447,8 +456,10 @@ static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
 		return res;
 
 	res = devres_alloc(pcim_intx_restore, sizeof(*res), GFP_KERNEL);
-	if (res)
+	if (res) {
+		save_orig_intx(pdev, res);
 		devres_add(dev, res);
+	}
 
 	return res;
 }
@@ -467,11 +478,10 @@ int pcim_intx(struct pci_dev *pdev, int enable)
 {
 	struct pcim_intx_devres *res;
 
-	res = get_or_create_intx_devres(&pdev->dev);
+	res = get_or_create_intx_devres(pdev);
 	if (!res)
 		return -ENOMEM;
 
-	res->orig_intx = !enable;
 	__pcim_intx(pdev, enable);
 
 	return 0;
-- 
2.43.0