[PATCH v4 4/9] PCI/PTM: Add pci_suspend_ptm() and pci_resume_ptm()

Bjorn Helgaas
2022-09-09T20:25:26Z

We disable PTM during suspend because that allows some Root Ports to enter
lower-power PM states, which means we also need to disable PTM for all
downstream devices. Add pci_suspend_ptm() and pci_resume_ptm() for this
purpose.

pci_enable_ptm() and pci_disable_ptm() are for drivers to use to enable or
disable PTM. They use dev->ptm_enabled to keep track of whether PTM should
be enabled.

pci_suspend_ptm() and pci_resume_ptm() are PCI core-internal functions to
temporarily disable PTM during suspend and (depending on dev->ptm_enabled)
re-enable PTM during resume.

Enable/disable/suspend/resume all use internal __pci_enable_ptm() and
__pci_disable_ptm() functions that only update the PTM Control register.
Outline:

pci_enable_ptm(struct pci_dev *dev)
{
__pci_enable_ptm(dev);
dev->ptm_enabled = 1;
pci_ptm_info(dev);
}

pci_disable_ptm(struct pci_dev *dev)
{
if (dev->ptm_enabled) {
__pci_disable_ptm(dev);
dev->ptm_enabled = 0;
}
}

pci_suspend_ptm(struct pci_dev *dev)
{
if (dev->ptm_enabled)
__pci_disable_ptm(dev);
}

pci_resume_ptm(struct pci_dev *dev)
{
if (dev->ptm_enabled)
__pci_enable_ptm(dev);
}

Nothing currently calls pci_resume_ptm(); the suspend path saves the PTM
state before disabling PTM, so the PTM state restore in the resume path
implicitly re-enables it. A future change will use pci_resume_ptm() to fix
some problems with this approach.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/pci.c | 4 +--
drivers/pci/pci.h | 6 ++--
drivers/pci/pcie/ptm.c | 71 +++++++++++++++++++++++++++++++++---------
include/linux/pci.h | 2 ++
4 files changed, 65 insertions(+), 18 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 95bc329e74c0..83818f81577d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2714,7 +2714,7 @@ int pci_prepare_to_sleep(struct pci_dev *dev)
* lower-power idle state as a whole.
*/
if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
- pci_disable_ptm(dev);
+ pci_suspend_ptm(dev);

pci_enable_wake(dev, target_state, wakeup);

@@ -2772,7 +2772,7 @@ int pci_finish_runtime_suspend(struct pci_dev *dev)
* lower-power idle state as a whole.
*/
if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
- pci_disable_ptm(dev);
+ pci_suspend_ptm(dev);

__pci_enable_wake(dev, target_state, pci_dev_run_wake(dev));

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 785f31086313..ce4a277e3f41 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -507,11 +507,13 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
#ifdef CONFIG_PCIE_PTM
void pci_save_ptm_state(struct pci_dev *dev);
void pci_restore_ptm_state(struct pci_dev *dev);
-void pci_disable_ptm(struct pci_dev *dev);
+void pci_suspend_ptm(struct pci_dev *dev);
+void pci_resume_ptm(struct pci_dev *dev);
#else
static inline void pci_save_ptm_state(struct pci_dev *dev) { }
static inline void pci_restore_ptm_state(struct pci_dev *dev) { }
-static inline void pci_disable_ptm(struct pci_dev *dev) { }
+static inline void pci_suspend_ptm(struct pci_dev *dev) { }
+static inline void pci_resume_ptm(struct pci_dev *dev) { }
#endif

unsigned long pci_cardbus_resource_alignment(struct resource *);
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index ba1d50c965fa..70a28b74e721 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -29,7 +29,7 @@ static void pci_ptm_info(struct pci_dev *dev)
dev->ptm_root ? " (root)" : "", clock_desc);
}

-void pci_disable_ptm(struct pci_dev *dev)
+static void __pci_disable_ptm(struct pci_dev *dev)
{
u16 ptm = dev->ptm_cap;
u16 ctrl;
@@ -42,6 +42,21 @@ void pci_disable_ptm(struct pci_dev *dev)
pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl);
}

+/**
+ * pci_disable_ptm() - Disable Precision Time Measurement
+ * @dev: PCI device
+ *
+ * Disable Precision Time Measurement for @dev.
+ */
+void pci_disable_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled) {
+ __pci_disable_ptm(dev);
+ dev->ptm_enabled = 0;
+ }
+}
+EXPORT_SYMBOL(pci_disable_ptm);
+
void pci_save_ptm_state(struct pci_dev *dev)
{
u16 ptm = dev->ptm_cap;
@@ -151,18 +166,8 @@ void pci_ptm_init(struct pci_dev *dev)
pci_enable_ptm(dev, NULL);
}

-/**
- * pci_enable_ptm() - Enable Precision Time Measurement
- * @dev: PCI device
- * @granularity: pointer to return granularity
- *
- * Enable Precision Time Measurement for @dev. If successful and
- * @granularity is non-NULL, return the Effective Granularity.
- *
- * Return: zero if successful, or -EINVAL if @dev lacks a PTM Capability or
- * is not a PTM Root and lacks an upstream path of PTM-enabled devices.
- */
-int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
+/* Enable PTM in the Control register if possible */
+static int __pci_enable_ptm(struct pci_dev *dev)
{
u16 ptm = dev->ptm_cap;
struct pci_dev *ups;
@@ -191,8 +196,29 @@ int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
ctrl |= PCI_PTM_CTRL_ROOT;

pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, ctrl);
+ return 0;
+}
+
+/**
+ * pci_enable_ptm() - Enable Precision Time Measurement
+ * @dev: PCI device
+ * @granularity: pointer to return granularity
+ *
+ * Enable Precision Time Measurement for @dev. If successful and
+ * @granularity is non-NULL, return the Effective Granularity.
+ *
+ * Return: zero if successful, or -EINVAL if @dev lacks a PTM Capability or
+ * is not a PTM Root and lacks an upstream path of PTM-enabled devices.
+ */
+int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
+{
+ int rc;
+
+ rc = __pci_enable_ptm(dev);
+ if (rc)
+ return rc;
+
dev->ptm_enabled = 1;
-
pci_ptm_info(dev);

if (granularity)
@@ -201,6 +227,23 @@ int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
}
EXPORT_SYMBOL(pci_enable_ptm);

+/*
+ * Disable PTM, but preserve dev->ptm_enabled so we silently re-enable it on
+ * resume if necessary.
+ */
+void pci_suspend_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled)
+ __pci_disable_ptm(dev);
+}
+
+/* If PTM was enabled before suspend, re-enable it when resuming */
+void pci_resume_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled)
+ __pci_enable_ptm(dev);
+}
+
bool pcie_ptm_enabled(struct pci_dev *dev)
{
if (!dev)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 54be939023a3..cb5f796e3319 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1678,10 +1678,12 @@ bool pci_ats_disabled(void);

#ifdef CONFIG_PCIE_PTM
int pci_enable_ptm(struct pci_dev *dev, u8 *granularity);
+void pci_disable_ptm(struct pci_dev *dev);
bool pcie_ptm_enabled(struct pci_dev *dev);
#else
static inline int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
{ return -EINVAL; }
+static inline void pci_disable_ptm(struct pci_dev *dev) { }
static inline bool pcie_ptm_enabled(struct pci_dev *dev)
{ return false; }
#endif
--
2.25.1