[PATCH v1 11/12] fpga: expose hardware error info in sysfs

[Russ Weight]

Extend the Intel Security Manager class driver to include
an optional update/hw_errinfo sysfs node that can be used
to retrieve 64 bits of device specific error information
following a secure update failure.

The underlying driver must provide a get_hw_errinfo() callback
function to enable this feature. This data is treated as
opaque by the class driver. It is left to user-space software
or support personnel to interpret this data.

Signed-off-by: Russ Weight <russell.h.weight@xxxxxxxxx>
Reviewed-by: Wu Hao <hao.wu@xxxxxxxxx>
---
 .../ABI/testing/sysfs-class-ifpga-sec-mgr     | 14 +++++++
 drivers/fpga/ifpga-sec-mgr.c                  | 38 +++++++++++++++++++
 include/linux/fpga/ifpga-sec-mgr.h            |  5 +++
 3 files changed, 57 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr b/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
index 762a7dee9453..20bde1abb5e4 100644
--- a/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
+++ b/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
@@ -135,3 +135,17 @@ Description:	Read-only. Returns a string describing the failure
 		idle state. If this file is read while a secure
 		update is in progress, then the read will fail with
 		EBUSY.
+
+What: 		/sys/class/ifpga_sec_mgr/ifpga_secX/update/hw_errinfo
+Date:		Sep 2020
+KernelVersion:  5.10
+Contact:	Russ Weight <russell.h.weight@xxxxxxxxx>
+Description:	Read-only. Returns a 64 bit error value providing
+		hardware specific information that may be useful in
+		debugging errors that occur during FPGA image updates.
+		This file is only visible if the underlying device
+		supports it. The hw_errinfo value is only accessible
+		when the secure update engine is in the idle state.
+		If this file is read while a secure update is in
+		progress, then the read will fail with EBUSY.
+		Format: "0x%llx".
diff --git a/drivers/fpga/ifpga-sec-mgr.c b/drivers/fpga/ifpga-sec-mgr.c
index afd97c135ebe..6944396eff80 100644
--- a/drivers/fpga/ifpga-sec-mgr.c
+++ b/drivers/fpga/ifpga-sec-mgr.c
@@ -152,10 +152,17 @@ static void set_error(struct ifpga_sec_mgr *imgr, enum ifpga_sec_err err_code)
 	imgr->err_code = err_code;
 }
 
+static void set_hw_errinfo(struct ifpga_sec_mgr *imgr)
+{
+	if (imgr->iops->get_hw_errinfo)
+		imgr->hw_errinfo = imgr->iops->get_hw_errinfo(imgr);
+}
+
 static void ifpga_sec_dev_error(struct ifpga_sec_mgr *imgr,
 				enum ifpga_sec_err err_code)
 {
 	set_error(imgr, err_code);
+	set_hw_errinfo(imgr);
 	imgr->iops->cancel(imgr);
 }
 
@@ -348,6 +355,23 @@ error_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(error);
 
+static ssize_t
+hw_errinfo_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct ifpga_sec_mgr *imgr = to_sec_mgr(dev);
+	int ret;
+
+	mutex_lock(&imgr->lock);
+	if (imgr->progress != IFPGA_SEC_PROG_IDLE)
+		ret = -EBUSY;
+	else
+		ret = sprintf(buf, "0x%llx\n", imgr->hw_errinfo);
+	mutex_unlock(&imgr->lock);
+
+	return ret;
+}
+static DEVICE_ATTR_RO(hw_errinfo);
+
 static ssize_t remaining_size_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
@@ -382,6 +406,7 @@ static ssize_t filename_store(struct device *dev, struct device_attribute *attr,
 		imgr->filename[strlen(imgr->filename) - 1] = '\0';
 
 	imgr->err_code = IFPGA_SEC_ERR_NONE;
+	imgr->hw_errinfo = 0;
 	imgr->request_cancel = false;
 	imgr->progress = IFPGA_SEC_PROG_READ_FILE;
 	reinit_completion(&imgr->update_done);
@@ -416,18 +441,31 @@ static ssize_t cancel_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_WO(cancel);
 
+static umode_t
+sec_mgr_update_visible(struct kobject *kobj, struct attribute *attr, int n)
+{
+	struct ifpga_sec_mgr *imgr = to_sec_mgr(kobj_to_dev(kobj));
+
+	if (attr == &dev_attr_hw_errinfo.attr && !imgr->iops->get_hw_errinfo)
+		return 0;
+
+	return attr->mode;
+}
+
 static struct attribute *sec_mgr_update_attrs[] = {
 	&dev_attr_filename.attr,
 	&dev_attr_cancel.attr,
 	&dev_attr_status.attr,
 	&dev_attr_error.attr,
 	&dev_attr_remaining_size.attr,
+	&dev_attr_hw_errinfo.attr,
 	NULL,
 };
 
 static struct attribute_group sec_mgr_update_attr_group = {
 	.name = "update",
 	.attrs = sec_mgr_update_attrs,
+	.is_visible = sec_mgr_update_visible,
 };
 
 static ssize_t name_show(struct device *dev,
diff --git a/include/linux/fpga/ifpga-sec-mgr.h b/include/linux/fpga/ifpga-sec-mgr.h
index f51ed663a723..3be8d8da078a 100644
--- a/include/linux/fpga/ifpga-sec-mgr.h
+++ b/include/linux/fpga/ifpga-sec-mgr.h
@@ -135,6 +135,9 @@ enum ifpga_sec_err {
  *			    function and is called at the completion
  *			    of the update, whether success or failure,
  *			    if the prepare function succeeded.
+ * @get_hw_errinfo:	    Optional: Return u64 hw specific error info.
+ *			    The software err_code may used to determine
+ *			    whether the hw error info is applicable.
  */
 struct ifpga_sec_mgr_ops {
 	sysfs_cnt_hndlr_t user_flash_count;
@@ -158,6 +161,7 @@ struct ifpga_sec_mgr_ops {
 	enum ifpga_sec_err (*poll_complete)(struct ifpga_sec_mgr *imgr);
 	void (*cleanup)(struct ifpga_sec_mgr *imgr);
 	enum ifpga_sec_err (*cancel)(struct ifpga_sec_mgr *imgr);
+	u64 (*get_hw_errinfo)(struct ifpga_sec_mgr *imgr);
 };
 
 /* Update progress codes */
@@ -183,6 +187,7 @@ struct ifpga_sec_mgr {
 	enum ifpga_sec_prog progress;
 	enum ifpga_sec_prog err_state;	/* progress state at time of failure */
 	enum ifpga_sec_err err_code;	/* security manager error code */
+	u64 hw_errinfo;			/* 64 bits of HW specific error info */
 	bool request_cancel;
 	bool driver_unload;
 	void *priv;
-- 
2.17.1