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>

1 files changed, 26 insertions, 0 deletions

diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index 31f38bc71a3d..6619cf1f6e1f 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/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),
 };