cxl: Workaround XSL bug that does not clear the RA bit after a reset

An issue was noted in our debug logs where the XSL would leave the RA
bit asserted after an AFU reset operation, which would effectively
prevent further AFU reset operations from working.

Workaround the issue by clearing the RA bit with an MMIO write if it is
still asserted after any AFU control operation.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index e77450567f6945d73f9f39e3ce34852e90d8eab6..04c27e41b654b0888428dcc078cffdad2b8dbdcc 100644 (file)
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -55,6 +55,16 @@ static int afu_control(struct cxl_afu *afu, u64 command, u64 clear,
                cpu_relax();
                AFU_Cntl = cxl_p2n_read(afu, CXL_AFU_Cntl_An);
        };
+
+       if (AFU_Cntl & CXL_AFU_Cntl_An_RA) {
+               /*
+                * Workaround for a bug in the XSL used in the Mellanox CX4
+                * that fails to clear the RA bit after an AFU reset,
+                * preventing subsequent AFU resets from working.
+                */
+               cxl_p2n_write(afu, CXL_AFU_Cntl_An, AFU_Cntl & ~CXL_AFU_Cntl_An_RA);
+       }
+
        pr_devel("AFU command complete: %llx\n", command);
        afu->enabled = enabled;
 out: