ocxl: control via sysfs whether the FPGA is reloaded on a link reset

Some opencapi FPGA images allow to control if the FPGA should be reloaded
on the next adapter reset. If it is supported, the image specifies it
through a Vendor Specific DVSEC in the config space of function 0.

Signed-off-by: Philippe Bergheaud <[e-mail]>
Signed-off-by: Frederic Barrat <[e-mail]>
Reviewed-by: Andrew Donnellan <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/ABI/testing/sysfs-class-ocxl

···
 Contact:	[e-mail]
 Description:	read/write
 		Give access the global mmio area for the AFU
+
+What:		/sys/class/ocxl/<afu name>/reload_on_reset
+Date:		February 2020
+Contact:	[e-mail]
+Description:	read/write
+		Control whether the FPGA is reloaded on a link reset. Enabled
+		through a vendor-specific logic block on the FPGA.
+			0	Do not reload FPGA image from flash
+			1	Reload FPGA image from flash
+			unavailable
+				The device does not support this capability

drivers/misc/ocxl/config.c

···
 	return 0;
 }
 
+/**
+ * get_function_0() - Find a related PCI device (function 0)
+ * @device: PCI device to match
+ *
+ * Returns a pointer to the related device, or null if not found
+ */
+static struct pci_dev *get_function_0(struct pci_dev *dev)
+{
+	unsigned int devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0);
+
+	return pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
+					   dev->bus->number, devfn);
+}
+
 static void read_pasid(struct pci_dev *dev, struct ocxl_fn_config *fn)
 {
 	u16 val;
···
 static int read_dvsec_vendor(struct pci_dev *dev)
 {
 	int pos;
-	u32 cfg, tlx, dlx;
+	u32 cfg, tlx, dlx, reset_reload;
 
 	/*
-	 * vendor specific DVSEC is optional
+	 * vendor specific DVSEC, for IBM images only. Some older
+	 * images may not have it
 	 *
-	 * It's currently only used on function 0 to specify the
-	 * version of some logic blocks. Some older images may not
-	 * even have it so we ignore any errors
+	 * It's only used on function 0 to specify the version of some
+	 * logic blocks and to give access to special registers to
+	 * enable host-based flashing.
 	 */
 	if (PCI_FUNC(dev->devfn) != 0)
 		return 0;
···
 	pci_read_config_dword(dev, pos + OCXL_DVSEC_VENDOR_CFG_VERS, &cfg);
 	pci_read_config_dword(dev, pos + OCXL_DVSEC_VENDOR_TLX_VERS, &tlx);
 	pci_read_config_dword(dev, pos + OCXL_DVSEC_VENDOR_DLX_VERS, &dlx);
+	pci_read_config_dword(dev, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
+			      &reset_reload);
 
 	dev_dbg(&dev->dev, "Vendor specific DVSEC:\n");
 	dev_dbg(&dev->dev, "  CFG version = 0x%x\n", cfg);
 	dev_dbg(&dev->dev, "  TLX version = 0x%x\n", tlx);
 	dev_dbg(&dev->dev, "  DLX version = 0x%x\n", dlx);
+	dev_dbg(&dev->dev, "  ResetReload = 0x%x\n", reset_reload);
+	return 0;
+}
+
+static int get_dvsec_vendor0(struct pci_dev *dev, struct pci_dev **dev0,
+			     int *out_pos)
+{
+	int pos;
+
+	if (PCI_FUNC(dev->devfn) != 0) {
+		dev = get_function_0(dev);
+		if (!dev)
+			return -1;
+	}
+	pos = find_dvsec(dev, OCXL_DVSEC_VENDOR_ID);
+	if (!pos)
+		return -1;
+	*dev0 = dev;
+	*out_pos = pos;
+	return 0;
+}
+
+int ocxl_config_get_reset_reload(struct pci_dev *dev, int *val)
+{
+	struct pci_dev *dev0;
+	u32 reset_reload;
+	int pos;
+
+	if (get_dvsec_vendor0(dev, &dev0, &pos))
+		return -1;
+
+	pci_read_config_dword(dev0, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
+			      &reset_reload);
+	*val = !!(reset_reload & BIT(0));
+	return 0;
+}
+
+int ocxl_config_set_reset_reload(struct pci_dev *dev, int val)
+{
+	struct pci_dev *dev0;
+	u32 reset_reload;
+	int pos;
+
+	if (get_dvsec_vendor0(dev, &dev0, &pos))
+		return -1;
+
+	pci_read_config_dword(dev0, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
+			      &reset_reload);
+	if (val)
+		reset_reload |= BIT(0);
+	else
+		reset_reload &= ~BIT(0);
+	pci_write_config_dword(dev0, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
+			       reset_reload);
 	return 0;
 }
 

drivers/misc/ocxl/ocxl_internal.h

···
 int ocxl_config_get_pasid_info(struct pci_dev *dev, int *count);
 
 /*
+ * Control whether the FPGA is reloaded on a link reset
+ */
+int ocxl_config_get_reset_reload(struct pci_dev *dev, int *val);
+int ocxl_config_set_reset_reload(struct pci_dev *dev, int val);
+
+/*
  * Check if an AFU index is valid for the given function.
  *
  * AFU indexes can be sparse, so a driver should check all indexes up

drivers/misc/ocxl/sysfs.c

···
 			afu->pasid_count, afu->pasid_max);
 }
 
+static ssize_t reload_on_reset_show(struct device *device,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct ocxl_afu *afu = to_afu(device);
+	struct ocxl_fn *fn = afu->fn;
+	struct pci_dev *pci_dev = to_pci_dev(fn->dev.parent);
+	int val;
+
+	if (ocxl_config_get_reset_reload(pci_dev, &val))
+		return scnprintf(buf, PAGE_SIZE, "unavailable\n");
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+
+static ssize_t reload_on_reset_store(struct device *device,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct ocxl_afu *afu = to_afu(device);
+	struct ocxl_fn *fn = afu->fn;
+	struct pci_dev *pci_dev = to_pci_dev(fn->dev.parent);
+	int rc, val;
+
+	rc = kstrtoint(buf, 0, &val);
+	if (rc || (val != 0 && val != 1))
+		return -EINVAL;
+
+	if (ocxl_config_set_reset_reload(pci_dev, val))
+		return -ENODEV;
+
+	return count;
+}
+
 static struct device_attribute afu_attrs[] = {
 	__ATTR_RO(global_mmio_size),
 	__ATTR_RO(pp_mmio_size),
 	__ATTR_RO(afu_version),
 	__ATTR_RO(contexts),
+	__ATTR_RW(reload_on_reset),
 };
 
 static ssize_t global_mmio_read(struct file *filp, struct kobject *kobj,

include/misc/ocxl-config.h

···
 #define   OCXL_DVSEC_VENDOR_CFG_VERS            0x0C
 #define   OCXL_DVSEC_VENDOR_TLX_VERS            0x10
 #define   OCXL_DVSEC_VENDOR_DLX_VERS            0x20
+#define   OCXL_DVSEC_VENDOR_RESET_RELOAD        0x38
 
 #endif /* _OCXL_CONFIG_H_ */