cxl: Allow the kernel to trust that an image won't change on PERST.

Provide a kernel API and a sysfs entry which allow a user to specify
that when a card is PERSTed, it's image will stay the same, allowing
it to participate in EEH.

cxl_reset is used to reflash the card. In that case, we cannot safely
assert that the image will not change. Therefore, disallow cxl_reset
if the flag is set.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Documentation/ABI/testing/sysfs-class-cxl

@@ -223,3 +223,13 @@ Description:    write only
                 Writing 1 will issue a PERST to card which may cause the card
                 to reload the FPGA depending on load_image_on_perst.
 Users:		https://github.com/ibm-capi/libcxl
+
+What:		/sys/class/cxl/<card>/perst_reloads_same_image
+Date:		July 2015
+Contact:	linuxppc-dev@lists.ozlabs.org
+Description:	read/write
+		Trust that when an image is reloaded via PERST, it will not
+		have changed.
+		0 = don't trust, the image may be different (default)
+		1 = trust that the image will not change.
+Users:		https://github.com/ibm-capi/libcxl

drivers/misc/cxl/api.c

@@ -327,3 +327,10 @@ int cxl_afu_reset(struct cxl_context *ctx)
 	return cxl_afu_check_and_enable(afu);
 }
 EXPORT_SYMBOL_GPL(cxl_afu_reset);
+
+void cxl_perst_reloads_same_image(struct cxl_afu *afu,
+				  bool perst_reloads_same_image)
+{
+	afu->adapter->perst_same_image = perst_reloads_same_image;
+}
+EXPORT_SYMBOL_GPL(cxl_perst_reloads_same_image);

drivers/misc/cxl/cxl.h

@@ -493,6 +493,7 @@ struct cxl {
 	bool user_image_loaded;
 	bool perst_loads_image;
 	bool perst_select_user;
+	bool perst_same_image;
 };
 
 int cxl_alloc_one_irq(struct cxl *adapter);

drivers/misc/cxl/pci.c

@@ -878,6 +878,12 @@ int cxl_reset(struct cxl *adapter)
 	int i;
 	u32 val;
 
+	if (adapter->perst_same_image) {
+		dev_warn(&dev->dev,
+			 "cxl: refusing to reset/reflash when perst_reloads_same_image is set.\n");
+		return -EINVAL;
+	}
+
 	dev_info(&dev->dev, "CXL reset\n");
 
 	/* pcie_warm_reset requests a fundamental pci reset which includes a
@@ -1151,6 +1157,7 @@ static struct cxl *cxl_init_adapter(struct pci_dev *dev)
 	 * configure/reconfigure
 	 */
 	adapter->perst_loads_image = true;
+	adapter->perst_same_image = false;
 
 	rc = cxl_configure_adapter(adapter, dev);
 	if (rc) {

drivers/misc/cxl/sysfs.c

@@ -112,12 +112,38 @@ static ssize_t load_image_on_perst_store(struct device *device,
 	return count;
 }
 
+static ssize_t perst_reloads_same_image_show(struct device *device,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct cxl *adapter = to_cxl_adapter(device);
+
+	return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->perst_same_image);
+}
+
+static ssize_t perst_reloads_same_image_store(struct device *device,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct cxl *adapter = to_cxl_adapter(device);
+	int rc;
+	int val;
+
+	rc = sscanf(buf, "%i", &val);
+	if ((rc != 1) || !(val == 1 || val == 0))
+		return -EINVAL;
+
+	adapter->perst_same_image = (val == 1 ? true : false);
+	return count;
+}
+
 static struct device_attribute adapter_attrs[] = {
 	__ATTR_RO(caia_version),
 	__ATTR_RO(psl_revision),
 	__ATTR_RO(base_image),
 	__ATTR_RO(image_loaded),
 	__ATTR_RW(load_image_on_perst),
+	__ATTR_RW(perst_reloads_same_image),
 	__ATTR(reset, S_IWUSR, NULL, reset_adapter_store),
 };
 

include/misc/cxl.h

@@ -200,4 +200,14 @@ unsigned int cxl_fd_poll(struct file *file, struct poll_table_struct *poll);
 ssize_t cxl_fd_read(struct file *file, char __user *buf, size_t count,
 			   loff_t *off);
 
+/*
+ * For EEH, a driver may want to assert a PERST will reload the same image
+ * from flash into the FPGA.
+ *
+ * This is a property of the entire adapter, not a single AFU, so drivers
+ * should set this property with care!
+ */
+void cxl_perst_reloads_same_image(struct cxl_afu *afu,
+				  bool perst_reloads_same_image);
+
 #endif /* _MISC_CXL_H */