[PATCH ath-next] wifi: ath10k: snoc: use memcpy_fromio() for MSA ramdump

[Linghui Wu]

On WCN3990/SNOC the MSA region is mapped with devm_memremap(MEMREMAP_WT).
On arm64 such a mapping is not Normal-cacheable, so unaligned accesses to
it are not permitted. ath10k_msa_dump_memory() copies the region with a
plain memcpy(), whose optimized __pi_memcpy_generic implementation issues
wide/unaligned loads. This triggers an alignment fault (FSC=0x21) Oops in
ath10k_snoc_fw_crashed_dump() while collecting the devcoredump:

  Unable to handle kernel paging request ... FSC=0x21: alignment fault
  pc : __pi_memcpy_generic
  lr : ath10k_snoc_fw_crashed_dump [ath10k_snoc]

The Oops both leaves the firmware RAM dump buffer zeroed (no dump is
captured) and crashes the kernel, which in turn breaks modem SSR
recovery.

Use memcpy_fromio(), which only performs accesses that are valid for such
a device-memory mapping. The generic memcpy_fromio() implementation aligns
the source before issuing word-sized reads and stores the destination with
put_unaligned(), so it is also safe for the coherent DMA allocation used on
the non-reserved-memory path. ath11k and ath12k use the same pattern
when copying target memory into crash dumps, so call it unconditionally
here too.
The MEMREMAP_WT pointer is a plain void *, so an explicit __iomem cast is
needed; use __force to keep sparse happy.

Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.3.7.c5-00107-QCAHLSWMTPL-1

Fixes: 3f14b73c3843 ("ath10k: Enable MSA region dump support for WCN3990")
Signed-off-by: Linghui Wu <linghui.wu@xxxxxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/ath10k/snoc.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/snoc.c b/drivers/net/wireless/ath/ath10k/snoc.c
index 310650227..695473eb0 100644
--- a/drivers/net/wireless/ath/ath10k/snoc.c
+++ b/drivers/net/wireless/ath/ath10k/snoc.c
@@ -7,6 +7,7 @@
 #include <linux/bits.h>
 #include <linux/clk.h>
+#include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
@@ -1475,11 +1476,15 @@ static void ath10k_msa_dump_memory(struct ath10k *ar,
 	hdr->length = cpu_to_le32(ar->msa.mem_size);
 
 	if (current_region->len < ar->msa.mem_size) {
-		memcpy(buf, ar->msa.vaddr, current_region->len);
+		memcpy_fromio(buf,
+			      (const void __iomem __force *)ar->msa.vaddr,
+			      current_region->len);
 		ath10k_warn(ar, "msa dump length is less than msa size %x, %x\n",
 			    current_region->len, ar->msa.mem_size);
 	} else {
-		memcpy(buf, ar->msa.vaddr, ar->msa.mem_size);
+		memcpy_fromio(buf,
+			      (const void __iomem __force *)ar->msa.vaddr,
+			      ar->msa.mem_size);
 	}
 }
 
base-commit: 913998f903fb1432c0046c33003db38a9e8bedb1
-- 
2.43.0