linux-kernel - [PATCH] drm/imagination: Fix timestamps in firmware traces

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20250221-fix-fw-trace-timestamps-v1-1-dba4aeb030ca@imgtec.com>
Date: Fri, 21 Feb 2025 10:49:35 +0000
From: Alessio Belle <alessio.belle@...tec.com>
To: Frank Binns <frank.binns@...tec.com>,
        Matt Coster
	<matt.coster@...tec.com>,
        Alexandru Dadu <alexandru.dadu@...tec.com>,
        "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>
CC: <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        "Alessio Belle" <alessio.belle@...tec.com>
Subject: [PATCH] drm/imagination: Fix timestamps in firmware traces

When firmware traces are enabled, the firmware dumps 48-bit timestamps
for each trace as two 32-bit values, highest 32 bits (of which only 16
useful) first.

The driver was reassembling them the other way round i.e. interpreting
the first value in memory as the lowest 32 bits, and the second value
as the highest 32 bits (then truncated to 16 bits).

Due to this, firmware trace dumps showed very large timestamps even for
traces recorded shortly after GPU boot. The timestamps in these dumps
would also sometimes jump backwards because of the truncation.

Example trace dumped after loading the powervr module and enabling
firmware traces, where each line is commented with the timestamp value
in hexadecimal to better show both issues:

[93540092739584] : Host Sync Partition marker: 1    // 0x551300000000
[28419798597632] : GPU units deinit                 // 0x19d900000000
[28548647616512] : GPU deinit                       // 0x19f700000000

Update logic to reassemble the timestamps halves in the correct order.

Fixes: cb56cd610866 ("drm/imagination: Add firmware trace to debugfs")
Signed-off-by: Alessio Belle <alessio.belle@...tec.com>
---
 drivers/gpu/drm/imagination/pvr_fw_trace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_fw_trace.c b/drivers/gpu/drm/imagination/pvr_fw_trace.c
index 73707daa4e52d13fd1388cb2e9feff0aea109620..5dbb636d7d4ffeea2253ea58e817710979f90cf0 100644
--- a/drivers/gpu/drm/imagination/pvr_fw_trace.c
+++ b/drivers/gpu/drm/imagination/pvr_fw_trace.c
@@ -333,8 +333,8 @@ static int fw_trace_seq_show(struct seq_file *s, void *v)
 	if (sf_id == ROGUE_FW_SF_LAST)
 		return -EINVAL;
 
-	timestamp = read_fw_trace(trace_seq_data, 1) |
-		((u64)read_fw_trace(trace_seq_data, 2) << 32);
+	timestamp = ((u64)read_fw_trace(trace_seq_data, 1) << 32) |
+		read_fw_trace(trace_seq_data, 2);
 	timestamp = (timestamp & ~ROGUE_FWT_TIMESTAMP_TIME_CLRMSK) >>
 		ROGUE_FWT_TIMESTAMP_TIME_SHIFT;
 

---
base-commit: 938fbb16aba8f7b88e0fdcf56f315a5bbad41aad
change-id: 20250220-fix-fw-trace-timestamps-15d70bb2d93d

Best regards,
-- 
Alessio Belle <alessio.belle@...tec.com>