[PATCH 2/4] PCI: Add new bitmap for keeping track of supported reset mechanisms

ameynarkhede03
2021-03-12T17:37:26Z

From: Amey Narkhede <ameynarkhede03@gmail.com>

Introduce a new bitmap reset_methods in struct pci_dev
to keep track of reset mechanisms supported by the
device. Also refactor probing and reset functions
to take advantage of calling convention of reset
functions.

Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
---
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

drivers/pci/pci.c | 106 ++++++++++++++++++++++++--------------------
drivers/pci/pci.h | 11 ++++-
drivers/pci/probe.c | 5 +--
include/linux/pci.h | 10 +++++
4 files changed, 79 insertions(+), 53 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4a7c084a3..407b44e85 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -40,6 +40,26 @@ const char *pci_power_names[] = {
};
EXPORT_SYMBOL_GPL(pci_power_names);

+static int pci_af_flr(struct pci_dev *dev, int probe);
+static int pci_pm_reset(struct pci_dev *dev, int probe);
+static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe);
+static int pci_parent_bus_reset(struct pci_dev *dev, int probe);
+
+/*
+ * The ordering for functions in pci_reset_fn_methods
+ * is required for bitmap positions defined
+ * in reset_methods in struct pci_dev
+ */
+const struct pci_reset_fn_method pci_reset_fn_methods[] = {
+ { .reset_fn = &pci_dev_specific_reset, .name = "device_specific" },
+ { .reset_fn = &pcie_flr, .name = "flr" },
+ { .reset_fn = &pci_af_flr, .name = "af_flr" },
+ { .reset_fn = &pci_pm_reset, .name = "pm" },
+ { .reset_fn = &pci_dev_reset_slot_function, .name = "slot" },
+ { .reset_fn = &pci_parent_bus_reset, .name = "bus" },
+ { 0 },
+};
+
int isa_dma_bridge_buggy;
EXPORT_SYMBOL(isa_dma_bridge_buggy);

@@ -5080,71 +5100,59 @@ static void pci_dev_restore(struct pci_dev *dev)
*/
int __pci_reset_function_locked(struct pci_dev *dev)
{
- int rc;
+ int i, rc = -ENOTTY;
+ const struct pci_reset_fn_method *reset;

might_sleep();

- /*
- * A reset method returns -ENOTTY if it doesn't support this device
- * and we should try the next method.
- *
- * If it returns 0 (success), we're finished. If it returns any
- * other error, we're also finished: this indicates that further
- * reset mechanisms might be broken on the device.
- */
- rc = pci_dev_specific_reset(dev, 0);
- if (rc != -ENOTTY)
- return rc;
- rc = pcie_flr(dev, 0);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_af_flr(dev, 0);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_pm_reset(dev, 0);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_dev_reset_slot_function(dev, 0);
- if (rc != -ENOTTY)
- return rc;
- return pci_parent_bus_reset(dev, 0);
+ for (i = 0, reset = pci_reset_fn_methods; reset->reset_fn; i++, reset++) {
+ if (!(dev->reset_methods & (1 << i)))
+ continue;
+
+ /*
+ * A reset method returns -ENOTTY if it doesn't support this device
+ * and we should try the next method.
+ *
+ * If it returns 0 (success), we're finished. If it returns any
+ * other error, we're also finished: this indicates that further
+ * reset mechanisms might be broken on the device.
+ */
+ rc = reset->reset_fn(dev, 0);
+ if (rc != -ENOTTY)
+ return rc;
+ }
+ return rc;
}
EXPORT_SYMBOL_GPL(__pci_reset_function_locked);

/**
- * pci_probe_reset_function - check whether the device can be safely reset
- * @dev: PCI device to reset
+ * pci_init_reset_methods - check whether device can be safely reset
+ * and store supported reset mechanisms.
+ * @dev: PCI device to check for reset mechanisms
*
* Some devices allow an individual function to be reset without affecting
* other functions in the same device. The PCI device must be responsive
- * to PCI config space in order to use this function.
+ * to reads and writes to its PCI config space in order to use this function.
*
- * Returns 0 if the device function can be reset or negative if the
- * device doesn't support resetting a single function.
+ * Stores reset mechanisms supported by device in reset_methods bitmap
+ * field of struct pci_dev
*/
-int pci_probe_reset_function(struct pci_dev *dev)
+void pci_init_reset_methods(struct pci_dev *dev)
{
- int rc;
+ int i, rc;
+ const struct pci_reset_fn_method *reset;

- might_sleep();
+ dev->reset_methods = 0;

- rc = pci_dev_specific_reset(dev, 1);
- if (rc != -ENOTTY)
- return rc;
- rc = pcie_flr(dev, 1);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_af_flr(dev, 1);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_pm_reset(dev, 1);
- if (rc != -ENOTTY)
- return rc;
- rc = pci_dev_reset_slot_function(dev, 1);
- if (rc != -ENOTTY)
- return rc;
+ might_sleep();

- return pci_parent_bus_reset(dev, 1);
+ for (i = 0, reset = pci_reset_fn_methods; reset->reset_fn; i++, reset++) {
+ rc = reset->reset_fn(dev, 1);
+ if (!rc)
+ dev->reset_methods |= (1 << i);
+ else if (rc != -ENOTTY)
+ break;
+ }
}

/**
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ef7c46613..ec093efdc 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -39,7 +39,7 @@ enum pci_mmap_api {
int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai,
enum pci_mmap_api mmap_api);

-int pci_probe_reset_function(struct pci_dev *dev);
+void pci_init_reset_methods(struct pci_dev *dev);
int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
int pci_bus_error_reset(struct pci_dev *dev);

@@ -612,6 +612,15 @@ struct pci_dev_reset_methods {
int (*reset)(struct pci_dev *dev, int probe);
};

+typedef int (*pci_reset_fn_t)(struct pci_dev *, int);
+
+struct pci_reset_fn_method {
+ pci_reset_fn_t reset_fn;
+ char *name;
+};
+
+extern const struct pci_reset_fn_method pci_reset_fn_methods[];
+
#ifdef CONFIG_PCI_QUIRKS
int pci_dev_specific_reset(struct pci_dev *dev, int probe);
#else
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 953f15abc..01dd037bd 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2403,9 +2403,8 @@ static void pci_init_capabilities(struct pci_dev *dev)
pci_rcec_init(dev); /* Root Complex Event Collector */

pcie_report_downtraining(dev);
-
- if (pci_probe_reset_function(dev) == 0)
- dev->reset_fn = 1;
+ pci_init_reset_methods(dev);
+ dev->reset_fn = !!dev->reset_methods;
}

/*
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 621ff5224..56d6e4750 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -325,6 +325,16 @@ struct pci_dev {
unsigned int class; /* 3 bytes: (base,sub,prog-if) */
u8 revision; /* PCI revision, low byte of class word */
u8 hdr_type; /* PCI header type (`multi' flag masked out) */
+ /*
+ * bit 0 -> dev_specific
+ * bit 1 -> flr
+ * bit 2 -> af_flr
+ * bit 3 -> pm
+ * bit 4 -> slot
+ * bit 5 -> bus
+ * See pci_reset_fn_methods array in pci.c
+ */
+ u8 __bitwise reset_methods; /* bitmap for device supported reset capabilities */
#ifdef CONFIG_PCIEAER
u16 aer_cap; /* AER capability offset */
struct aer_stats *aer_stats; /* AER stats for this device */
--
2.30.2