platform/chrome: wilco_ec: Add h1_gpio status to debugfs

As part of Chrome OS's FAFT (Fully Automated Firmware Testing)
tests, we need to ensure that the H1 chip is properly setting
some GPIO lines. The h1_gpio attribute exposes the state
of the lines:
- ENTRY_TO_FACT_MODE in BIT(0)
- SPI_CHROME_SEL in BIT(1)

There are two reasons that I am exposing this in debugfs,
and not as a GPIO:
1. This is only useful for testing, so end users shouldn't ever
care about this. In fact, if it passes the tests, then the value of
h1_gpio will always be 2, so it would be really uninteresting for users.
2. This GPIO is not connected to, controlled by, or really even related
to the AP. The GPIO runs between the EC and the H1 security chip.

Changes in v4:
- Use "0x02x\n" instead of "02x\n" for format string
- Use DEFINE_DEBUGFS_ATTRIBUTE()
- Add documentation
Changes in v3:
- Fix documentation to correspond with formatting change in v2.
Changes in v2:
- Zero out the unused fields in the request.
- Format result as "%02x\n" instead of as a decimal.
Signed-off-by: Nick Crews <ncrews@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Documentation/ABI/testing/debugfs-wilco-ec

+What:		/sys/kernel/debug/wilco_ec/h1_gpio
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		As part of Chrome OS's FAFT (Fully Automated Firmware Testing)
+		tests, we need to ensure that the H1 chip is properly setting
+		some GPIO lines. The h1_gpio attribute exposes the state
+		of the lines:
+		- ENTRY_TO_FACT_MODE in BIT(0)
+		- SPI_CHROME_SEL in BIT(1)
+
+		Output will formatted with "0x%02x\n".
+
 What:		/sys/kernel/debug/wilco_ec/raw
 Date:		January 2019
 KernelVersion:	5.1

drivers/platform/chrome/wilco_ec/debugfs.c

@@ -164,6 +164,51 @@ static const struct file_operations fops_raw = {
 	.llseek = no_llseek,
 };
 
+#define CMD_KB_CHROME		0x88
+#define SUB_CMD_H1_GPIO		0x0A
+
+struct h1_gpio_status_request {
+	u8 cmd;		/* Always CMD_KB_CHROME */
+	u8 reserved;
+	u8 sub_cmd;	/* Always SUB_CMD_H1_GPIO */
+} __packed;
+
+struct hi_gpio_status_response {
+	u8 status;	/* 0 if allowed */
+	u8 val;		/* BIT(0)=ENTRY_TO_FACT_MODE, BIT(1)=SPI_CHROME_SEL */
+} __packed;
+
+static int h1_gpio_get(void *arg, u64 *val)
+{
+	struct wilco_ec_device *ec = arg;
+	struct h1_gpio_status_request rq;
+	struct hi_gpio_status_response rs;
+	struct wilco_ec_message msg;
+	int ret;
+
+	memset(&rq, 0, sizeof(rq));
+	rq.cmd = CMD_KB_CHROME;
+	rq.sub_cmd = SUB_CMD_H1_GPIO;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.type = WILCO_EC_MSG_LEGACY;
+	msg.request_data = &rq;
+	msg.request_size = sizeof(rq);
+	msg.response_data = &rs;
+	msg.response_size = sizeof(rs);
+	ret = wilco_ec_mailbox(ec, &msg);
+	if (ret < 0)
+		return ret;
+	if (rs.status)
+		return -EIO;
+
+	*val = rs.val;
+
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_h1_gpio, h1_gpio_get, NULL, "0x%02llx\n");
+
 /**
  * wilco_ec_debugfs_probe() - Create the debugfs node
  * @pdev: The platform device, probably created in core.c
@@ -185,6 +230,8 @@ static int wilco_ec_debugfs_probe(struct platform_device *pdev)
 	if (!debug_info->dir)
 		return 0;
 	debugfs_create_file("raw", 0644, debug_info->dir, NULL, &fops_raw);
+	debugfs_create_file("h1_gpio", 0444, debug_info->dir, ec,
+			    &fops_h1_gpio);
 
 	return 0;
 }