Re: [PATCH libdrm v1 2/2] tests/modetest: Add support for writeback connector

[Rohith Iyer <quic_rohiiyer@xxxxxxxxxxx>]

Hi Andy,

On 7/25/2022 6:57 PM, Andy Yan wrote:
> Hi Rohith:
>
>
>
>
> At 2022-07-26 03:26:39, "Rohith Iyer" <quic_rohiiyer@xxxxxxxxxxx> wrote:
> > Add writeback support to modetest with the below options:
>
> > +		case 'o':
> > +			pipe_args->dump = true;
> > +			dump_path = optarg;
> > +			break;
> > 		case 'P':
> > 			plane_args = realloc(plane_args,
> > 					     (plane_count + 1) * sizeof *plane_args);
> > @@ -2098,6 +2173,7 @@ int main(int argc, char **argv)
> > 			crtcs = 1;
> > 			planes = 1;
> > 			break;
> > +		case 'x':
> > 		case 's':
> > 			pipe_args = realloc(pipe_args,
> > 					    (count + 1) * sizeof *pipe_args);
> > @@ -2109,7 +2185,7 @@ int main(int argc, char **argv)
> >
> > 			if (parse_connector(&pipe_args[count], optarg) < 0)
> > 				usage(argv[0]);
> > -
> > +			pipe_args->custom = (c == 'x');
> > 			count++;
> > 			break;
> > 		case 'C':
> > @@ -2165,6 +2241,7 @@ int main(int argc, char **argv)
> >
> > 	if (use_atomic) {
> > 		ret = drmSetClientCap(dev.fd, DRM_CLIENT_CAP_ATOMIC, 1);
> > +		drmSetClientCap(dev.fd, DRM_CLIENT_CAP_WRITEBACK_CONNECTORS, 1);
> > 		if (ret) {
> > 			fprintf(stderr, "no atomic modesetting support: %s\n", strerror(errno));
> > 			drmClose(dev.fd);
> > @@ -2208,6 +2285,8 @@ int main(int argc, char **argv)
> > 			if (set_preferred || count)
> > 				set_mode(&dev, pipe_args, count);
> >
> > +			writeback_config(&dev, pipe_args, count);
> > +
> > 			if (plane_count)
> > 				atomic_set_planes(&dev, plane_args, plane_count, false);
> >
> > @@ -2217,6 +2296,13 @@ int main(int argc, char **argv)
> > 				return 1;
> > 			}
>
> >
>
>
> How do we make sure the writeback is finished?  Do we need a writeback fence here?

Thanks for pointing this out. We plan to have a function that polls on 
the writeback fence fd, until the writeback is finished. Let me know if 
you have something else in mind.

> > +			/*
> > +			 * Since only writeback connectors have an output fb, this should only be
> > +			 * called for writeback.
> > +			 */
> > +			if (pipe_args->dump)
> > +				dump_output_fb(&dev, pipe_args, dump_path, count);
> > +
> > 			if (test_vsync)
> > 				atomic_test_page_flip(&dev, pipe_args, plane_args, plane_count);
> >
> > --
> > 2.31.0

Thanks,
Rohith