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PCI/ASPM: Add pci_enable_link_state_locked()

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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: f492edb40b ("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: Johan Hovold <johan+linaro@kernel.org>
[bhelgaas: include helper name in subject, commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan 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>
This commit is contained in:
Johan Hovold 2023-11-28 09:15:07 +01:00 committed by Bjorn Helgaas
parent ef61a04057
commit 718ab82266
2 changed files with 43 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
drivers/pci/pcie/aspm.c
View File

@ -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);
@ -1136,7 +1126,8 @@ int pci_enable_link_state(struct pci_dev *pdev, int state)
return -EPERM;
}
down_read(&pci_bus_sem);
if (!locked)
down_read(&pci_bus_sem);
mutex_lock(&aspm_lock);
link->aspm_default = 0;
if (state & PCIE_LINK_STATE_L0S)
@ -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);
up_read(&pci_bus_sem);
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)
{

3
include/linux/pci.h
View File

@ -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; }