On 21/02/2025 10:49, Alessio Belle wrote:
> 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@xxxxxxxxxx>
Reviewed-by: Matt Coster <matt.coster@xxxxxxxxxx>
Cheers,
Matt
> ---
> 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@xxxxxxxxxx>
>
--
Matt Coster
E: matt.coster@xxxxxxxxxx
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