Re: [igt-dev] [PATCH i-g-t v5 1/6] lib/igt_kms: Add writeback support

Liviu Dudau
2019-03-18T10:41:28Z

On Wed, Mar 06, 2019 at 06:30:05PM -0300, Rodrigo Siqueira wrote:
> Hi Liviu,
>
> I’m using your patchset to guide my implementation of writeback in the
> VKMS, so, first of all, thanks :)
>
> During my work, I noticed that you’re setting the drmSetClientCap()
> before drmModeGetResources() which make the writeback capability

before? I believe your patchset moves it to be before, which makes
sense, as the writeback applies to connectors, not planes (sorry for the
confusion, I think I wrote the code when we were toying with the idea
that writeback was going to be a plane property).

> ‘invisible’ for drmModeGetResources(). I made the following change, and
> I could pass the igt_display_require():
>
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index f4ff3a96..bb2d8e06 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -1912,6 +1912,12 @@ void igt_display_require(igt_display_t *display, int drm_fd)
>
> display->drm_fd = drm_fd;
>
> + drmSetClientCap(drm_fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
> + if (drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0)
> + display->is_atomic = 1;
> +
> + drmSetClientCap(drm_fd, DRM_CLIENT_CAP_WRITEBACK_CONNECTORS, 1);
> +
> resources = drmModeGetResources(display->drm_fd);
> if (!resources)
> goto out;
> @@ -1924,12 +1930,6 @@ void igt_display_require(igt_display_t *display, int drm_fd)
> display->pipes = calloc(sizeof(igt_pipe_t), display->n_pipes);
> igt_assert_f(display->pipes, "Failed to allocate memory for %d pipes\n", display->n_pipes);
>
> - drmSetClientCap(drm_fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
> - if (drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0)
> - display->is_atomic = 1;
> -
> - drmSetClientCap(drm_fd, DRM_CLIENT_CAP_WRITEBACK_CONNECTORS, 1);
> -
> plane_resources = drmModeGetPlaneResources(display->drm_fd);
> igt_assert(plane_resources);
>
> I'm not 100% confident about this issue, because of this I will send an
> RFC and see if I can get more details about this issue.

It actually looks correct to me, so

Acked-by: Liviu Dudau <liviu.dudau@arm.com>

>
> Additionally, if you need any help with this patchset I will be glad to
> help since I’m using it \o/

Well, I need to send an updated version and if you could review that
then I can merge it into igt.

Best regards,
Liviu

>
> Best Regards
> Rodrigo Siqueira
>
> On 02/04, Brian Starkey wrote:
> > Hi Liviu,
> >
> > On Tue, Jan 15, 2019 at 05:47:42PM +0000, Liviu Dudau wrote:
> > > From: Brian Starkey <brian.starkey@arm.com>
> >
> > [snip]
> >
> > >
> > > +/**
> > > + * igt_output_set_writeback_fb:
> > > + * @output: Target output
> > > + * @fb: Target framebuffer
> > > + *
> > > + * This function sets the given @fb to be used as the target framebuffer for the
> > > + * writeback engine at the next atomic commit. It will also request a writeback
> > > + * out fence that will contain the fd number of the out fence created by KMS if
> > > + * the given @fb is valid.
> > > + */
> > > +void igt_output_set_writeback_fb(igt_output_t *output, struct igt_fb *fb)
> > > +{
> > > + igt_display_t *display = output->display;
> > > +
> > > + LOG(display, "%s: output_set_writeback_fb(%d)\n", output->name, fb ? fb->fb_id : 0);
> > > +
> > > + igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_FB_ID, fb ? fb->fb_id : 0);
> > > + /* only request a writeback out fence if the framebuffer is valid */
> > > + if (fb)
> > > + igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR,
> > > + (ptrdiff_t)&output->writeback_out_fence_fd);
> >
> > I'm still not sure (ptrdiff_t) is the right type here, (uintptr_t)
> > seems better.
> >
> > Thanks,
> > -Brian
> > _______________________________________________
> > igt-dev mailing list
> > igt-dev@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/igt-dev
>
> --
> Rodrigo Siqueira
> https://siqueira.tech
> Graduate Student
> Department of Computer Science
> University of São Paulo

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