[PATCH] drm/xe: Get XE_FORCEWAKE_ALL to read RING_TIMESTAMP

[Umesh Nerlige Ramappa]

On Mon, Jun 24, 2024 at 09:44:03AM -0500, Lucas De Marchi wrote:
>On Sat, Jun 22, 2024 at 03:23:25AM GMT, Umesh Nerlige Ramappa wrote:
>>Per client engine utilization uses RING_TIMESTAMP to return
>>drm-total-cycles to the user. We read only the rcs RING_TIMESTAMP in
>>platforms that have render. While this works for rcs and
>>ccs, it is observed that this value is 0 when running work on bcs, vcs
>>and vecs. Ideally we should read the engine specific RING_TIMESTAMP, but
>
>what do you mean by engine specific RING_TIMESTAMP? We are already
>reading the engine specific copy of the same timestamp.

We read RING_TIMESTAMP from the first available engine which in my case 
was rcs (DG2).

> AFAIR just getting the gt fw was working for reading this register 
> from vcs, vecs, bcs.

Well, issue could be DG2 specific, haven't tried other platforms. Which 
platforms did you run it on? I will try to use the same.

>Can you demonstrate the failure with a bug open or a series of
>intel_reg invocations showing otherwise?

This was found while running tests in this series, so I don't see any 
open bugs.

https://patchwork.freedesktop.org/series/135204/

xe_drm_fdinfo --r drm-busy-idle --debug 

>
>I think the simplest way to show it doesn't work is to call
>`intel_reg write` to get a GT forcewake, then `intel_reg read` to read
>this register.

Don't know how to use this on Xe, I get a sigsegv.

sudo ./intel_reg write 0x2358 0x00c0ffee
Received signal SIGSEGV.
Stack trace:
  #0 [fatal_sig_handler+0x175]
  #1 [__sigaction+0x50]
  #2 [intel_reg_write+0x589]
  #3 [main+0x339]
  #4 [__libc_init_first+0x90]
  #5 [__libc_start_main+0x80]
  #6 [_start+0x25]
Segmentation fault (core dumped)

Regards,
Umesh

>
>Lucas De Marchi
>
>>to keep the logic simple, just get XE_FORCEWAKE_ALL instead of XE_GT_FW.
>>
>>This should work fine on multi-gt platforms as well since the
>>gt_timestamp is in sync on all GTs.
>>
>>Fixes: 188ced1e0ff8 ("drm/xe/client: Print runtime to fdinfo")
>>Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
>>---
>>drivers/gpu/drm/xe/xe_drm_client.c | 4 ++--
>>1 file changed, 2 insertions(+), 2 deletions(-)
>>
>>diff --git a/drivers/gpu/drm/xe/xe_drm_client.c b/drivers/gpu/drm/xe/xe_drm_client.c
>>index 4a19b771e3a0..74f2244679f3 100644
>>--- a/drivers/gpu/drm/xe/xe_drm_client.c
>>+++ b/drivers/gpu/drm/xe/xe_drm_client.c
>>@@ -264,9 +264,9 @@ static void show_run_ticks(struct drm_printer *p, struct drm_file *file)
>>		if (!hwe)
>>			continue;
>>
>>-		xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
>>+		xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL);
>>		gpu_timestamp = xe_hw_engine_read_timestamp(hwe);
>>-		xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
>>+		xe_force_wake_put(gt_to_fw(gt), XE_FORCEWAKE_ALL);
>>		break;
>>	}
>>
>>-- 
>>2.34.1
>>