[PATCH v6 3/6] fpga: m10bmc-sec: expose max10 flash update count

[Russ Weight]

Extend the MAX10 BMC Secure Update driver to provide a
sysfs file to expose the flash update count for the FPGA
user image.

Signed-off-by: Russ Weight <russell.h.weight@xxxxxxxxx>
Reviewed-by: Tom Rix <trix@xxxxxxxxxx>
---
v6:
  - Changed flash_count_show() parameter list to achieve
    reverse-christmas tree format.
  - Added WARN_ON() call for (FLASH_COUNT_SIZE / stride) to ensure
    that the proper count is passed to regmap_bulk_read().
v5:
  - Renamed sysfs node user_flash_count to flash_count and updated the
    sysfs documentation accordingly.
v4:
  - Moved the sysfs file for displaying the flash count from the
    FPGA Security Manager class driver to here. The
    m10bmc_user_flash_count() function is removed and the
    functionality is moved into a user_flash_count_show()
    function.
  - Added ABI documentation for the new sysfs entry
v3:
  - Changed: iops -> sops, imgr -> smgr, IFPGA_ -> FPGA_, ifpga_ to fpga_
  - Changed "MAX10 BMC Secure Engine driver" to "MAX10 BMC Secure Update
    driver"
  - Removed wrapper functions (m10bmc_raw_*, m10bmc_sys_*). The
    underlying functions are now called directly.
v2:
  - Renamed get_qspi_flash_count() to m10bmc_user_flash_count()
  - Minor code cleanup per review comments
  - Added m10bmc_ prefix to functions in m10bmc_iops structure
---
 .../testing/sysfs-driver-intel-m10-bmc-secure |  8 ++++
 drivers/fpga/intel-m10-bmc-secure.c           | 37 +++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
index 2992488b717a..73a3aba750e8 100644
--- a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
+++ b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
@@ -27,3 +27,11 @@ Description:	Read only. Returns the root entry hash for the BMC image
 		"hash not programmed".  This file is only visible if the
 		underlying device supports it.
 		Format: "0x%x".
+
+What:		/sys/bus/platform/devices/n3000bmc-secure.*.auto/security/flash_count
+Date:		Oct 2020
+KernelVersion:  5.11
+Contact:	Russ Weight <russell.h.weight@xxxxxxxxx>
+Description:	Read only. Returns number of times the secure update
+		staging area has been flashed.
+		Format: "%u".
diff --git a/drivers/fpga/intel-m10-bmc-secure.c b/drivers/fpga/intel-m10-bmc-secure.c
index 5ac5f59b5731..ecd63c13cb2d 100644
--- a/drivers/fpga/intel-m10-bmc-secure.c
+++ b/drivers/fpga/intel-m10-bmc-secure.c
@@ -11,6 +11,7 @@
 #include <linux/mfd/intel-m10-bmc.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/slab.h>
 
 struct m10bmc_sec {
 	struct device *dev;
@@ -78,7 +79,43 @@ DEVICE_ATTR_SEC_REH_RO(bmc, BMC_PROG_MAGIC, BMC_PROG_ADDR, BMC_REH_ADDR);
 DEVICE_ATTR_SEC_REH_RO(sr, SR_PROG_MAGIC, SR_PROG_ADDR, SR_REH_ADDR);
 DEVICE_ATTR_SEC_REH_RO(pr, PR_PROG_MAGIC, PR_PROG_ADDR, PR_REH_ADDR);
 
+#define FLASH_COUNT_SIZE 4096	/* count stored as inverted bit vector */
+
+static ssize_t flash_count_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct m10bmc_sec *sec = dev_get_drvdata(dev);
+	unsigned int stride, num_bits;
+	u8 *flash_buf;
+	int cnt, ret;
+
+	stride = regmap_get_reg_stride(sec->m10bmc->regmap);
+	num_bits = FLASH_COUNT_SIZE * 8;
+
+	flash_buf = kmalloc(FLASH_COUNT_SIZE, GFP_KERNEL);
+	if (!flash_buf)
+		return -ENOMEM;
+
+	WARN_ON(FLASH_COUNT_SIZE % stride);
+	ret = regmap_bulk_read(sec->m10bmc->regmap, STAGING_FLASH_COUNT,
+			       flash_buf, FLASH_COUNT_SIZE / stride);
+	if (ret) {
+		dev_err(sec->dev,
+			"failed to read flash count: %x cnt %x: %d\n",
+			STAGING_FLASH_COUNT, FLASH_COUNT_SIZE / stride, ret);
+		goto exit_free;
+	}
+	cnt = num_bits - bitmap_weight((unsigned long *)flash_buf, num_bits);
+
+exit_free:
+	kfree(flash_buf);
+
+	return ret ? : sysfs_emit(buf, "%u\n", cnt);
+}
+static DEVICE_ATTR_RO(flash_count);
+
 static struct attribute *m10bmc_security_attrs[] = {
+	&dev_attr_flash_count.attr,
 	&dev_attr_bmc_root_entry_hash.attr,
 	&dev_attr_sr_root_entry_hash.attr,
 	&dev_attr_pr_root_entry_hash.attr,
-- 
2.25.1