cxl/pci: Fix CDAT retrieval on big endian

The CDAT exposed in sysfs differs between little endian and big endian
arches:  On big endian, every 4 bytes are byte-swapped.

PCI Configuration Space is little endian (PCI r3.0 sec 6.1).  Accessors
such as pci_read_config_dword() implicitly swap bytes on big endian.
That way, the macros in include/uapi/linux/pci_regs.h work regardless of
the arch's endianness.  For an example of implicit byte-swapping, see
ppc4xx_pciex_read_config(), which calls in_le32(), which uses lwbrx
(Load Word Byte-Reverse Indexed).

DOE Read/Write Data Mailbox Registers are unlike other registers in
Configuration Space in that they contain or receive a 4 byte portion of
an opaque byte stream (a "Data Object" per PCIe r6.0 sec 7.9.24.5f).
They need to be copied to or from the request/response buffer verbatim.
So amend pci_doe_send_req() and pci_doe_recv_resp() to undo the implicit
byte-swapping.

The CXL_DOE_TABLE_ACCESS_* and PCI_DOE_DATA_OBJECT_DISC_* macros assume
implicit byte-swapping.  Byte-swap requests after constructing them with
those macros and byte-swap responses before parsing them.

Change the request and response type to __le32 to avoid sparse warnings.
Per a request from Jonathan, replace sizeof(u32) with sizeof(__le32) for
consistency.

Fixes: c97006046c79 ("cxl/port: Read CDAT table")
Tested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: stable@vger.kernel.org # v6.0+
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/3051114102f41d19df3debbee123129118fc5e6d.1678543498.git.lukas@wunner.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 7328a2552411..49a99a84b6aa 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -462,7 +462,7 @@ static struct pci_doe_mb *find_cdat_doe(struct device *uport)
 	return NULL;
 }
 
-#define CDAT_DOE_REQ(entry_handle)					\
+#define CDAT_DOE_REQ(entry_handle) cpu_to_le32				\
 	(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE,			\
 		    CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) |		\
 	 FIELD_PREP(CXL_DOE_TABLE_ACCESS_TABLE_TYPE,			\
@@ -475,8 +475,8 @@ static void cxl_doe_task_complete(struct pci_doe_task *task)
 }
 
 struct cdat_doe_task {
-	u32 request_pl;
-	u32 response_pl[32];
+	__le32 request_pl;
+	__le32 response_pl[32];
 	struct completion c;
 	struct pci_doe_task task;
 };
@@ -510,10 +510,10 @@ static int cxl_cdat_get_length(struct device *dev,
 		return rc;
 	}
 	wait_for_completion(&t.c);
-	if (t.task.rv < sizeof(u32))
+	if (t.task.rv < sizeof(__le32))
 		return -EIO;
 
-	*length = t.response_pl[1];
+	*length = le32_to_cpu(t.response_pl[1]);
 	dev_dbg(dev, "CDAT length %zu\n", *length);
 
 	return 0;
@@ -524,13 +524,13 @@ static int cxl_cdat_read_table(struct device *dev,
 			       struct cxl_cdat *cdat)
 {
 	size_t length = cdat->length;
-	u32 *data = cdat->table;
+	__le32 *data = cdat->table;
 	int entry_handle = 0;
 
 	do {
 		DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(entry_handle), t);
 		size_t entry_dw;
-		u32 *entry;
+		__le32 *entry;
 		int rc;
 
 		rc = pci_doe_submit_task(cdat_doe, &t.task);
@@ -540,21 +540,21 @@ static int cxl_cdat_read_table(struct device *dev,
 		}
 		wait_for_completion(&t.c);
 		/* 1 DW header + 1 DW data min */
-		if (t.task.rv < (2 * sizeof(u32)))
+		if (t.task.rv < (2 * sizeof(__le32)))
 			return -EIO;
 
 		/* Get the CXL table access header entry handle */
 		entry_handle = FIELD_GET(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE,
-					 t.response_pl[0]);
+					 le32_to_cpu(t.response_pl[0]));
 		entry = t.response_pl + 1;
-		entry_dw = t.task.rv / sizeof(u32);
+		entry_dw = t.task.rv / sizeof(__le32);
 		/* Skip Header */
 		entry_dw -= 1;
-		entry_dw = min(length / sizeof(u32), entry_dw);
+		entry_dw = min(length / sizeof(__le32), entry_dw);
 		/* Prevent length < 1 DW from causing a buffer overflow */
 		if (entry_dw) {
-			memcpy(data, entry, entry_dw * sizeof(u32));
-			length -= entry_dw * sizeof(u32);
+			memcpy(data, entry, entry_dw * sizeof(__le32));
+			length -= entry_dw * sizeof(__le32);
 			data += entry_dw;
 		}
 	} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);