linux-kernel - [PATCH] platform/x86/intel/pmt: Sapphire Rapids PMT errata fix

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Date:   Fri,  4 Nov 2022 20:42:28 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     david.e.box@...ux.intel.com, hdegoede@...hat.com,
        markgross@...nel.org
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] platform/x86/intel/pmt: Sapphire Rapids PMT errata fix

On Sapphire Rapids, due to a hardware issue affecting the PUNIT telemetry
region, reads that are not done in QWORD quantities and alignment may
return incorrect data. Use a custom 64-bit copy for this region.

Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
---
 drivers/platform/x86/intel/pmt/class.c | 31 +++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c
index 53d7fd2943b4..46598dcb634a 100644
--- a/drivers/platform/x86/intel/pmt/class.c
+++ b/drivers/platform/x86/intel/pmt/class.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/pci.h>
@@ -19,6 +20,7 @@
 #define PMT_XA_START		0
 #define PMT_XA_MAX		INT_MAX
 #define PMT_XA_LIMIT		XA_LIMIT(PMT_XA_START, PMT_XA_MAX)
+#define GUID_SPR_PUNIT		0x9956f43f
 
 bool intel_pmt_is_early_client_hw(struct device *dev)
 {
@@ -33,6 +35,29 @@ bool intel_pmt_is_early_client_hw(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(intel_pmt_is_early_client_hw);
 
+static inline int
+pmt_memcpy64_fromio(void *to, const u64 __iomem *from, size_t count)
+{
+	int i, remain;
+	u64 *buf = to;
+
+	if (!IS_ALIGNED((unsigned long)from, 8))
+		return -EFAULT;
+
+	for (i = 0; i < count/8; i++)
+		buf[i] = readq(&from[i]);
+
+	/* Copy any remaining bytes */
+	remain = count % 8;
+	if (remain) {
+		u64 tmp = readq(&from[i]);
+
+		memcpy(&buf[i], &tmp, remain);
+	}
+
+	return count;
+}
+
 /*
  * sysfs
  */
@@ -54,7 +79,11 @@ intel_pmt_read(struct file *filp, struct kobject *kobj,
 	if (count > entry->size - off)
 		count = entry->size - off;
 
-	memcpy_fromio(buf, entry->base + off, count);
+	if (entry->guid == GUID_SPR_PUNIT)
+		/* PUNIT on SPR only supports aligned 64-bit read */
+		count = pmt_memcpy64_fromio(buf, entry->base + off, count);
+	else
+		memcpy_fromio(buf, entry->base + off, count);
 
 	return count;
 }

base-commit: 225469d4acbcb873358d7618bad6e0203b67b964
-- 
2.25.1