Re: [igt-dev] [PATCH i-g-t 1/3] lib/i915: Return actual submission method from gem_submission_method

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Thu, 28 Oct 2021 16:55:32 -0700, John Harrison wrote:
>
> On 10/27/2021 21:40, Ashutosh Dixit wrote:
> > gem_submission_method() purports to return the currently used submission
> > method by the kernel, as evidenced by its callers. Therefore remove the
> > GEM_SUBMISSION_EXECLISTS flag when GuC submission is detected.
> >
> > This also fixes gem_has_execlists() to match its description, previously
> > gem_has_execlists() would return true even if GuC submission was actually
> > being used in the driver.
> >
> > v2: Or gem_has_execlists call-sites with gem_has_guc_submission to make the
> >      new code equivalent to the previous code.
> > v3: Clarify that submission method is either guc (0x4), execlists (0x2) or
> >      legacy without semaphores (0x0) or legacy with semaphores (0x1)
>
> What about GuC with semaphores vs GuC without semaphores? Likewise execlist.
>
> Semaphores is not a submission method. They are a submission feature whose
> support or lack there of is independent of the submission method.

Sorry I didn't know that. But if you see gem_submission_method() in current
upstream IGT (pasted below) it doesn't return "GuC with semaphores' or
"execlist with semaphores" either. Anyway, let me do this in the next
rev. Thanks.

unsigned gem_submission_method(int fd)
{
	const int gen = intel_gen(intel_get_drm_devid(fd));
	unsigned flags = 0;

	int dir;

	dir = igt_params_open(fd);
	if (dir < 0)
		return 0;

	if (igt_sysfs_get_u32(dir, "enable_guc") & 1) {
		flags |= GEM_SUBMISSION_GUC | GEM_SUBMISSION_EXECLISTS;
		goto out;
	}

	if (gen >= 8) {
		flags |= GEM_SUBMISSION_EXECLISTS;
		goto out;
	}

	if (has_semaphores(fd, dir))
		flags |= GEM_SUBMISSION_SEMAPHORES;

out:
	close(dir);
	return flags;
}