Commit 718ab822 authored by Johan Hovold's avatar Johan Hovold Committed by Bjorn Helgaas
Browse files

PCI/ASPM: Add pci_enable_link_state_locked() 

Add pci_enable_link_state_locked() for enabling link states that can be
used in contexts where a pci_bus_sem read lock is already held (e.g. from
pci_walk_bus()).

This helper will be used to fix a couple of potential deadlocks where
the current helper is called with the lock already held, hence the CC
stable tag.

Fixes: f492edb4 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
Link: https://lore.kernel.org/r/20231128081512.19387-2-johan+linaro@kernel.org


Signed-off-by: default avatarJohan Hovold <johan+linaro@kernel.org>
[bhelgaas: include helper name in subject, commit log]
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: <stable@vger.kernel.org>	# 6.3
Cc: Michael Bottini <michael.a.bottini@linux.intel.com>
Cc: David E. Box <david.e.box@linux.intel.com>
parent ef61a040

drivers/pci/pcie/aspm.c

+40 −13
Original line number Diff line number Diff line
@@ -1109,17 +1109,7 @@ int pci_disable_link_state(struct pci_dev *pdev, int state) 
}

EXPORT_SYMBOL(pci_disable_link_state);



/**

 * pci_enable_link_state - Clear and set the default device link state so that

 * the link may be allowed to enter the specified states. Note that if the

 * BIOS didn't grant ASPM control to the OS, this does nothing because we can't

 * touch the LNKCTL register. Also note that this does not enable states

 * disabled by pci_disable_link_state(). Return 0 or a negative errno.

 *

 * @pdev: PCI device

 * @state: Mask of ASPM link states to enable

 */

int pci_enable_link_state(struct pci_dev *pdev, int state)

static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)

{

	struct pcie_link_state *link = pcie_aspm_get_link(pdev);
@@ -1136,6 +1126,7 @@ int pci_enable_link_state(struct pci_dev *pdev, int state) 
		return -EPERM;

	}



	if (!locked)

		down_read(&pci_bus_sem);

	mutex_lock(&aspm_lock);

	link->aspm_default = 0;
@@ -1157,12 +1148,48 @@ int pci_enable_link_state(struct pci_dev *pdev, int state) 
	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;

	pcie_set_clkpm(link, policy_to_clkpm_state(link));

	mutex_unlock(&aspm_lock);

	if (!locked)

		up_read(&pci_bus_sem);



	return 0;

}



/**

 * pci_enable_link_state - Clear and set the default device link state so that

 * the link may be allowed to enter the specified states. Note that if the

 * BIOS didn't grant ASPM control to the OS, this does nothing because we can't

 * touch the LNKCTL register. Also note that this does not enable states

 * disabled by pci_disable_link_state(). Return 0 or a negative errno.

 *

 * @pdev: PCI device

 * @state: Mask of ASPM link states to enable

 */

int pci_enable_link_state(struct pci_dev *pdev, int state)

{

	return __pci_enable_link_state(pdev, state, false);

}

EXPORT_SYMBOL(pci_enable_link_state);



/**

 * pci_enable_link_state_locked - Clear and set the default device link state

 * so that the link may be allowed to enter the specified states. Note that if

 * the BIOS didn't grant ASPM control to the OS, this does nothing because we

 * can't touch the LNKCTL register. Also note that this does not enable states

 * disabled by pci_disable_link_state(). Return 0 or a negative errno.

 *

 * @pdev: PCI device

 * @state: Mask of ASPM link states to enable

 *

 * Context: Caller holds pci_bus_sem read lock.

 */

int pci_enable_link_state_locked(struct pci_dev *pdev, int state)

{

	lockdep_assert_held_read(&pci_bus_sem);



	return __pci_enable_link_state(pdev, state, true);

}

EXPORT_SYMBOL(pci_enable_link_state_locked);



static int pcie_aspm_set_policy(const char *val,

				const struct kernel_param *kp)

{

include/linux/pci.h

+3 −0
Original line number Diff line number Diff line
@@ -1829,6 +1829,7 @@ extern bool pcie_ports_native; 
int pci_disable_link_state(struct pci_dev *pdev, int state);

int pci_disable_link_state_locked(struct pci_dev *pdev, int state);

int pci_enable_link_state(struct pci_dev *pdev, int state);

int pci_enable_link_state_locked(struct pci_dev *pdev, int state);

void pcie_no_aspm(void);

bool pcie_aspm_support_enabled(void);

bool pcie_aspm_enabled(struct pci_dev *pdev);
@@ -1839,6 +1840,8 @@ static inline int pci_disable_link_state_locked(struct pci_dev *pdev, int state) 
{ return 0; }

static inline int pci_enable_link_state(struct pci_dev *pdev, int state)

{ return 0; }

static inline int pci_enable_link_state_locked(struct pci_dev *pdev, int state)

{ return 0; }

static inline void pcie_no_aspm(void) { }

static inline bool pcie_aspm_support_enabled(void) { return false; }

static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; }