[PATCH 4/5] PCI / PM: Check for error when reading Power State

Bjorn Helgaas
2019-08-05T20:52:39Z

From: Bjorn Helgaas <bhelgaas@google.com>

The Power Management Status Register is in config space, and reads while
the device is in D3cold typically return ~0 data (PCI_ERROR_RESPONSE). If
we just look at the PCI_PM_CTRL_STATE_MASK bits, that is 0x3, which looks
like D3hot, not D3cold.

Check the entire register for PCI_ERROR_RESPONSE so we can distinguish
D3cold from D3hot.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/pci.c | 6 +++---
include/linux/pci.h | 13 +++++++++++++
2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index af6a97d7012b..d8686e3cd5eb 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -894,7 +894,7 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
udelay(PCI_PM_D2_DELAY);

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
- dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
+ dev->current_state = pci_power_state(pmcsr);
if (dev->current_state != state && printk_ratelimit())
pci_info(dev, "Refused to change power state, currently in D%d\n",
dev->current_state);
@@ -942,7 +942,7 @@ void pci_update_current_state(struct pci_dev *dev, pci_power_t state)
u16 pmcsr;

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
- dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
+ dev->current_state = pci_power_state(pmcsr);
} else {
dev->current_state = state;
}
@@ -1677,7 +1677,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
if (dev->pm_cap) {
u16 pmcsr;
pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
- dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
+ dev->current_state = pci_power_state(pmcsr);
}

if (atomic_inc_return(&dev->enable_cnt) > 1)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d64fd3788061..fdfe990e9661 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -152,6 +152,19 @@ static inline const char *pci_power_name(pci_power_t state)
return pci_power_names[1 + (__force int) state];
}

+/*
+ * Convert a Power Management Status Register value to a pci_power_t.
+ * Note that if we read the register while the device is in D3cold, we
+ * typically get PCI_ERROR_RESPONSE, which looks like D3hot (0x3) if we
+ * only look at the PCI_PM_CTRL_STATE_MASK bits.
+ */
+static inline pci_power_t pci_power_state(u16 pmcsr)
+{
+ if (pmcsr == (u16) PCI_ERROR_RESPONSE)
+ return PCI_D3cold;
+ return pmcsr & PCI_PM_CTRL_STATE_MASK;
+}
+
#define PCI_PM_D2_DELAY 200
#define PCI_PM_D3_WAIT 10
#define PCI_PM_D3COLD_WAIT 100
--
2.22.0.770.g0f2c4a37fd-goog