From e9a9970bf520c99e530d8f1fa5b5c22671fad4ef Mon Sep 17 00:00:00 2001
From: Russ Weight <russell.h.weight@intel.com>
Date: Thu, 16 Sep 2021 14:07:33 -0700
Subject: [PATCH] fpga: dfl: Avoid reads to AFU CSRs during enumeration
Git-commit: e9a9970bf520c99e530d8f1fa5b5c22671fad4ef
Patch-mainline: v5.15-rc3
References: jsc#PED-1263

CSR address space for Accelerator Functional Units (AFU) is not available
during the early Device Feature List (DFL) enumeration. Early access
to this space results in invalid data and port errors. This change adds
a condition to prevent an early read from the AFU CSR space.

Fixes: 1604986c3e6b ("fpga: dfl: expose feature revision from struct dfl_device")
Cc: stable@vger.kernel.org
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/fpga/dfl.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index c99b78ee008a..f86666cf2c6a 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -1019,16 +1019,18 @@ create_feature_instance(struct build_feature_devs_info *binfo,
 {
 	unsigned int irq_base, nr_irqs;
 	struct dfl_feature_info *finfo;
+	u8 revision = 0;
 	int ret;
-	u8 revision;
 	u64 v;
 
-	v = readq(binfo->ioaddr + ofst);
-	revision = FIELD_GET(DFH_REVISION, v);
+	if (fid != FEATURE_ID_AFU) {
+		v = readq(binfo->ioaddr + ofst);
+		revision = FIELD_GET(DFH_REVISION, v);
 
-	/* read feature size and id if inputs are invalid */
-	size = size ? size : feature_size(v);
-	fid = fid ? fid : feature_id(v);
+		/* read feature size and id if inputs are invalid */
+		size = size ? size : feature_size(v);
+		fid = fid ? fid : feature_id(v);
+	}
 
 	if (binfo->len - ofst < size)
 		return -EINVAL;
-- 
2.35.3