[PATCH] drm/etnaviv: print MMU exception cause

[Lucas Stach <l.stach@xxxxxxxxxxxxxx>]

From: Christian Gmeiner <christian.gmeiner@xxxxxxxxx>

The MMU tells us the fault status. While the raw register value is
already printed, it's a bit more user friendly to translate the
fault reasons into human readable format.

Signed-off-by: Christian Gmeiner <christian.gmeiner@xxxxxxxxx>
Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
I've rewritten parts of the patch to properly cover multiple
MMUs and squashed the reason into the existing message. Christian,
please tell me if you are fine with having your name attached to
this patch.
---
 drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
index 37018bc55810..f79203b774d9 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
@@ -1426,6 +1426,15 @@ static void sync_point_worker(struct work_struct *work)
 
 static void dump_mmu_fault(struct etnaviv_gpu *gpu)
 {
+	static const char *fault_reasons[] = {
+		"slave not present",
+		"page not present",
+		"write violation",
+		"out of bounds",
+		"read security violation",
+		"write security violation",
+	};
+
 	u32 status_reg, status;
 	int i;
 
@@ -1438,18 +1447,25 @@ static void dump_mmu_fault(struct etnaviv_gpu *gpu)
 	dev_err_ratelimited(gpu->dev, "MMU fault status 0x%08x\n", status);
 
 	for (i = 0; i < 4; i++) {
+		const char *reason = "unknown";
 		u32 address_reg;
+		u32 mmu_status;
 
-		if (!(status & (VIVS_MMUv2_STATUS_EXCEPTION0__MASK << (i * 4))))
+		mmu_status = (status >> (i * 4)) & VIVS_MMUv2_STATUS_EXCEPTION0__MASK;
+		if (!mmu_status)
 			continue;
 
+		if ((mmu_status - 1) < ARRAY_SIZE(fault_reasons))
+			reason = fault_reasons[mmu_status - 1];
+
 		if (gpu->sec_mode == ETNA_SEC_NONE)
 			address_reg = VIVS_MMUv2_EXCEPTION_ADDR(i);
 		else
 			address_reg = VIVS_MMUv2_SEC_EXCEPTION_ADDR;
 
-		dev_err_ratelimited(gpu->dev, "MMU %d fault addr 0x%08x\n", i,
-				    gpu_read(gpu, address_reg));
+		dev_err_ratelimited(gpu->dev,
+				    "MMU %d fault (%s) addr 0x%08x\n",
+				    i, reason, gpu_read(gpu, address_reg));
 	}
 }
 
-- 
2.30.2