3 files changed, 100 insertions, 0 deletions

diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index 9f280e3e742e..cfee819bf5d4 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -360,6 +360,10 @@ struct cxl_afu {
 	struct mutex spa_mutex;
 	spinlock_t afu_cntl_lock;
 
+	/* AFU error buffer fields and bin attribute for sysfs */
+	u64 eb_len, eb_offset;
+	struct bin_attribute attr_eb;
+
 	/*
 	 * Only the first part of the SPA is used for the process element
 	 * linked list. The only other part that software needs to worry about
@@ -561,6 +565,9 @@ static inline void __iomem *_cxl_p2n_addr(struct cxl_afu *afu, cxl_p2n_reg_t reg
 u16 cxl_afu_cr_read16(struct cxl_afu *afu, int cr, u64 off);
 u8 cxl_afu_cr_read8(struct cxl_afu *afu, int cr, u64 off);
 
+ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
+				loff_t off, size_t count);
+
 
 struct cxl_calls {
 	void (*cxl_slbia)(struct mm_struct *mm);
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 1ef01647265f..c3671b3c4dcd 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -593,6 +593,22 @@ static int cxl_read_afu_descriptor(struct cxl_afu *afu)
 	afu->crs_len = AFUD_CR_LEN(val) * 256;
 	afu->crs_offset = AFUD_READ_CR_OFF(afu);
 
+
+	/* eb_len is in multiple of 4K */
+	afu->eb_len = AFUD_EB_LEN(AFUD_READ_EB(afu)) * 4096;
+	afu->eb_offset = AFUD_READ_EB_OFF(afu);
+
+	/* eb_off is 4K aligned so lower 12 bits are always zero */
+	if (EXTRACT_PPC_BITS(afu->eb_offset, 0, 11) != 0) {
+		dev_warn(&afu->dev,
+			 "Invalid AFU error buffer offset %Lx\n",
+			 afu->eb_offset);
+		dev_info(&afu->dev,
+			 "Ignoring AFU error buffer in the descriptor\n");
+		/* indicate that no afu buffer exists */
+		afu->eb_len = 0;
+	}
+
 	return 0;
 }
 
@@ -672,6 +688,50 @@ static int sanitise_afu_regs(struct cxl_afu *afu)
 	return 0;
 }
 
+#define ERR_BUFF_MAX_COPY_SIZE PAGE_SIZE
+/*
+ * afu_eb_read:
+ * Called from sysfs and reads the afu error info buffer. The h/w only supports
+ * 4/8 bytes aligned access. So in case the requested offset/count arent 8 byte
+ * aligned the function uses a bounce buffer which can be max PAGE_SIZE.
+ */
+ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
+				loff_t off, size_t count)
+{
+	loff_t aligned_start, aligned_end;
+	size_t aligned_length;
+	void *tbuf;
+	const void __iomem *ebuf = afu->afu_desc_mmio + afu->eb_offset;
+
+	if (count == 0 || off < 0 || (size_t)off >= afu->eb_len)
+		return 0;
+
+	/* calculate aligned read window */
+	count = min((size_t)(afu->eb_len - off), count);
+	aligned_start = round_down(off, 8);
+	aligned_end = round_up(off + count, 8);
+	aligned_length = aligned_end - aligned_start;
+
+	/* max we can copy in one read is PAGE_SIZE */
+	if (aligned_length > ERR_BUFF_MAX_COPY_SIZE) {
+		aligned_length = ERR_BUFF_MAX_COPY_SIZE;
+		count = ERR_BUFF_MAX_COPY_SIZE - (off & 0x7);
+	}
+
+	/* use bounce buffer for copy */
+	tbuf = (void *)__get_free_page(GFP_TEMPORARY);
+	if (!tbuf)
+		return -ENOMEM;
+
+	/* perform aligned read from the mmio region */
+	memcpy_fromio(tbuf, ebuf + aligned_start, aligned_length);
+	memcpy(buf, tbuf + (off & 0x7), count);
+
+	free_page((unsigned long)tbuf);
+
+	return count;
+}
+
 static int cxl_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
 {
 	struct cxl_afu *afu;
diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index d0c38c7bc0c4..4942d55ba77f 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/drivers/misc/cxl/sysfs.c
@@ -356,6 +356,16 @@ static ssize_t api_version_compatible_show(struct device *device,
 	return scnprintf(buf, PAGE_SIZE, "%i\n", CXL_API_VERSION_COMPATIBLE);
 }
 
+static ssize_t afu_eb_read(struct file *filp, struct kobject *kobj,
+			       struct bin_attribute *bin_attr, char *buf,
+			       loff_t off, size_t count)
+{
+	struct cxl_afu *afu = to_cxl_afu(container_of(kobj,
+						      struct device, kobj));
+
+	return cxl_afu_read_err_buffer(afu, buf, off, count);
+}
+
 static struct device_attribute afu_attrs[] = {
 	__ATTR_RO(mmio_size),
 	__ATTR_RO(irqs_min),
@@ -534,6 +544,10 @@ void cxl_sysfs_afu_remove(struct cxl_afu *afu)
 	struct afu_config_record *cr, *tmp;
 	int i;
 
+	/* remove the err buffer bin attribute */
+	if (afu->eb_len)
+		device_remove_bin_file(&afu->dev, &afu->attr_eb);
+
 	for (i = 0; i < ARRAY_SIZE(afu_attrs); i++)
 		device_remove_file(&afu->dev, &afu_attrs[i]);
 
@@ -555,6 +569,22 @@ int cxl_sysfs_afu_add(struct cxl_afu *afu)
 			goto err;
 	}
 
+	/* conditionally create the add the binary file for error info buffer */
+	if (afu->eb_len) {
+		afu->attr_eb.attr.name = "afu_err_buff";
+		afu->attr_eb.attr.mode = S_IRUGO;
+		afu->attr_eb.size = afu->eb_len;
+		afu->attr_eb.read = afu_eb_read;
+
+		rc = device_create_bin_file(&afu->dev, &afu->attr_eb);
+		if (rc) {
+			dev_err(&afu->dev,
+				"Unable to create eb attr for the afu. Err(%d)\n",
+				rc);
+			goto err;
+		}
+	}
+
 	for (i = 0; i < afu->crs_num; i++) {
 		cr = cxl_sysfs_afu_new_cr(afu, i);
 		if (IS_ERR(cr)) {
@@ -570,6 +600,9 @@ err1:
 	cxl_sysfs_afu_remove(afu);
 	return rc;
 err:
+	/* reset the eb_len as we havent created the bin attr */
+	afu->eb_len = 0;
+
 	for (i--; i >= 0; i--)
 		device_remove_file(&afu->dev, &afu_attrs[i]);
 	return rc;