[PATCH 3/3] hwmon: (occ) Provide the SBEFIFO FFDC in binary sysfs

[Eddie James <eajames@xxxxxxxxxxxxx>]

Save any FFDC provided by the OCC driver, and provide it to userspace
through a binary sysfs entry. Do some basic state management to
ensure that userspace can always collect the data if there was an
error. Notify polling userspace when there is an error too.

Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
---
 drivers/hwmon/occ/p9_sbe.c | 98 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 97 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/occ/p9_sbe.c b/drivers/hwmon/occ/p9_sbe.c
index 9709f2b9c052..505f489832a4 100644
--- a/drivers/hwmon/occ/p9_sbe.c
+++ b/drivers/hwmon/occ/p9_sbe.c
@@ -4,18 +4,54 @@
 #include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/fsi-occ.h>
+#include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
 
 #include "common.h"
 
+enum sbe_error_state {
+	SBE_ERROR_NONE = 0,
+	SBE_ERROR_PENDING,
+	SBE_ERROR_COLLECTED
+};
+
 struct p9_sbe_occ {
 	struct occ occ;
+	int sbe_error;
+	void *ffdc;
+	size_t ffdc_len;
+	size_t ffdc_size;
+	struct mutex sbe_error_lock;	/* lock access to ffdc data */
+	u32 no_ffdc_magic;
 	struct device *sbe;
 };
 
 #define to_p9_sbe_occ(x)	container_of((x), struct p9_sbe_occ, occ)
 
+static ssize_t sbe_error_read(struct file *filp, struct kobject *kobj,
+			      struct bin_attribute *battr, char *buf,
+			      loff_t pos, size_t count)
+{
+	ssize_t rc = 0;
+	struct occ *occ = dev_get_drvdata(kobj_to_dev(kobj));
+	struct p9_sbe_occ *ctx = to_p9_sbe_occ(occ);
+
+	mutex_lock(&ctx->sbe_error_lock);
+	if (ctx->sbe_error == SBE_ERROR_PENDING) {
+		rc = memory_read_from_buffer(buf, count, &pos, ctx->ffdc,
+					     ctx->ffdc_len);
+		ctx->sbe_error = SBE_ERROR_COLLECTED;
+	}
+	mutex_unlock(&ctx->sbe_error_lock);
+
+	return rc;
+}
+static BIN_ATTR_RO(sbe_error, OCC_MAX_RESP_WORDS * 4);
+
 static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd, size_t len)
 {
 	struct occ_response *resp = &occ->resp;
@@ -24,8 +60,47 @@ static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd, size_t len)
 	int rc;
 
 	rc = fsi_occ_submit(ctx->sbe, cmd, len, resp, &resp_len);
-	if (rc < 0)
+	if (rc < 0) {
+		if (resp_len) {
+			bool notify = false;
+
+			mutex_lock(&ctx->sbe_error_lock);
+			if (ctx->sbe_error != SBE_ERROR_PENDING)
+				notify = true;
+			ctx->sbe_error = SBE_ERROR_PENDING;
+
+			if (resp_len > ctx->ffdc_size) {
+				if (ctx->ffdc_size)
+					kvfree(ctx->ffdc);
+				ctx->ffdc = kvmalloc(resp_len, GFP_KERNEL);
+				if (!ctx->ffdc) {
+					ctx->ffdc_size = 0;
+					ctx->ffdc_len = sizeof(u32);
+					ctx->ffdc = &ctx->no_ffdc_magic;
+					goto unlock;
+				}
+
+				ctx->ffdc_size = resp_len;
+			}
+
+			ctx->ffdc_len = resp_len;
+			memcpy(ctx->ffdc, resp, resp_len);
+
+unlock:
+			mutex_unlock(&ctx->sbe_error_lock);
+
+			if (notify)
+				sysfs_notify(&occ->bus_dev->kobj, NULL,
+					     bin_attr_sbe_error.attr.name);
+		}
+
 		return rc;
+	}
+
+	mutex_lock(&ctx->sbe_error_lock);
+	if (ctx->sbe_error == SBE_ERROR_COLLECTED)
+		ctx->sbe_error = SBE_ERROR_NONE;
+	mutex_unlock(&ctx->sbe_error_lock);
 
 	switch (resp->return_status) {
 	case OCC_RESP_CMD_IN_PRG:
@@ -65,6 +140,13 @@ static int p9_sbe_occ_probe(struct platform_device *pdev)
 	if (!ctx)
 		return -ENOMEM;
 
+	ctx->no_ffdc_magic = OCC_NO_FFDC_MAGIC;
+	ctx->sbe_error = SBE_ERROR_NONE;
+	ctx->ffdc = &ctx->no_ffdc_magic;
+	ctx->ffdc_len = sizeof(u32);
+	ctx->ffdc_size = 0;
+	mutex_init(&ctx->sbe_error_lock);
+
 	ctx->sbe = pdev->dev.parent;
 	occ = &ctx->occ;
 	occ->bus_dev = &pdev->dev;
@@ -78,6 +160,15 @@ static int p9_sbe_occ_probe(struct platform_device *pdev)
 	if (rc == -ESHUTDOWN)
 		rc = -ENODEV;	/* Host is shutdown, don't spew errors */
 
+	if (!rc) {
+		rc = device_create_bin_file(occ->bus_dev, &bin_attr_sbe_error);
+		if (rc) {
+			dev_warn(occ->bus_dev,
+				 "failed to create SBE error ffdc file\n");
+			rc = 0;
+		}
+	}
+
 	return rc;
 }
 
@@ -86,9 +177,14 @@ static int p9_sbe_occ_remove(struct platform_device *pdev)
 	struct occ *occ = platform_get_drvdata(pdev);
 	struct p9_sbe_occ *ctx = to_p9_sbe_occ(occ);
 
+	device_remove_bin_file(occ->bus_dev, &bin_attr_sbe_error);
+
 	ctx->sbe = NULL;
 	occ_shutdown(occ);
 
+	if (ctx->ffdc_size)
+		kvfree(ctx->ffdc);
+
 	return 0;
 }
 
-- 
2.27.0