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linux-rt-devel@lists.linux.dev, amd-gfx@lists.freedesktop.org, Alex Deucher , Mario Limonciello , Sebastian Andrzej Siewior , Thomas Gleixner , spasswolf@web.de Date: Mon, 27 Jul 2026 00:52:34 +0200 In-Reply-To: <6e0b713cffd64b3c30eb4ff04e50721bac9cf8ca.camel@web.de> References: <20260723131001.11565-1-spasswolf@web.de> <1a0800888c2fcd42f1fcd661d8f6f50580ac2fd4.camel@web.de> <4d7c2dd588cd77d1d112da473f2a262d22051d57.camel@web.de> <3c1be47abfcc907e7c1f9696cb25a24c93415a28.camel@web.de> <4af8467060c5ee136c2b99ab855a007fec4e8c6c.camel@web.de> <6e0b713cffd64b3c30eb4ff04e50721bac9cf8ca.camel@web.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.2-10 Precedence: bulk X-Mailing-List: linux-next@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:fQqRly0LUPpdwL8qtkC/cnwRdENIppHpNDrnPiks9ISos/IxKLA VCDI2g4zKBKAj9sPX4jX6H7gibixsmoa8P257XKAoYT6SPP0IlC5/oxjE+Ghqcn8ZcW8rbQ 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+rF+ynCOxIfSseoLr53nVKVaXtJUR0/9u4kHg5lpl4Mkg4TEGID92bnehseZF0netEa6JDtYl h7P6M5SLdkHGUgQ/Vk8C8cobz97JuZkGzBQ7C9JjXWfYvTP+zkEPjDT0G+geA8hESLt56GMVJ GJwJh3dwi3Of6cTzc1sqfDSMGjK3uuBjYH7FtDyDqYvsFaeWTeNXj/roTPXsIVXPddPX4ufTF /+VwxnxpuzuTO3dN3B8rdXAMmm5IZMv85ad735c Am Sonntag, dem 26.07.2026 um 20:47 +0200 schrieb Bert Karwatzki: > Am Sonntag, dem 26.07.2026 um 01:16 +0200 schrieb Bert Karwatzki: >=20 >=20 > Now I've run a test with > commit 8bf0cb97edb ("drm/amd/display: Move dml2_destroy to non-FPU compi= lation unit") > with the following debugging patch: >=20 As I had no better idea I started throwing printk()s into the general=20 direction of the bug, and found this after some attempts: /*************************************************************************= ****** * Public functions *************************************************************************= *****/ struct dc_plane_state *dc_create_plane_state(const struct dc *dc) { printk(KERN_INFO "%s %d: preempt_count =3D %d\n", __func__, __LINE__, pre= empt_count()); struct dc_plane_state *plane_state =3D kvzalloc_obj(*plane_state, GFP_ATOMIC); printk(KERN_INFO "%s %d\n", __func__, __LINE__); if (NULL =3D=3D plane_state) return NULL; kref_init(&plane_state->refcount); dc_plane_construct(dc->ctx, plane_state); return plane_state; } In the error case this prints "preempt_count =3D 2"! (only if dc_create_pl= ane_state() is called from dc_state_create_phantom_plane()). If I combine this with the "solution" from above diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resourc= e.c b/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c index cb93bfbe9e9e..7a90098ec118 100644 =2D-- a/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c @@ -1693,11 +1693,9 @@ enum dc_status dcn401_validate_bandwidth(struct dc = *dc, } =20 if (dc->debug.using_dml2) { - DC_FP_START(); status =3D dml2_validate(dc, context, context->power_source =3D=3D DC_POWER_SOUR= CE_DC ? context->bw_ctx.dml2_dc_power_source : context->bw_ctx.dml2, validate_mode) ? DC_OK : DC_FAIL_BANDWIDTH= _VALIDATE; - DC_FP_END(); } =20 if (validate_mode =3D=3D DC_VALIDATE_MODE_AND_PROGRAMMING && statu= s =3D=3D DC_OK && dc_state_is_subvp_in_use(context)) { @@ -1718,11 +1716,9 @@ enum dc_status dcn401_validate_bandwidth(struct dc = *dc, if (validate_mode =3D=3D DC_VALIDATE_MODE_AND_PROGRAMMING && statu= s =3D=3D DC_FAIL_HW_CURSOR_SUPPORT) { /* attempt to validate again with subvp disabled due to cu= rsor */ if (dc->debug.using_dml2) { - DC_FP_START(); status =3D dml2_validate(dc, context, context->power_source =3D=3D DC_PO= WER_SOURCE_DC ? context->bw_ctx.dml2_dc_power_source : context->bw_ctx.dml= 2, validate_mode) ? DC_OK : DC_FAIL_B= ANDWIDTH_VALIDATE; - DC_FP_END(); } } =20 I get in all cases "preempt_count =3D 0" again. I also monitored the preempt_count with this patch applied on top of commit 02c3060ee303 ("drm/amdgpu: add support to query vram info from firmware") (this is the last commit before the problematic patchset 32c1c35b6d8b drm/amd/display: Move FPU Guards From DML To DC - Part 3 4bb2f0721ed8 drm/amd/display: Move FPU Guards From DML To DC - Part 2 3539437f354b drm/amd/display: Move FPU Guards From DML To DC - Part 1) diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c b/drivers/gp= u/drm/amd/display/dc/core/dc_surface.c index 5f12dcca7f71..29f45b556371 100644 =2D-- a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_surface.c @@ -85,6 +85,7 @@ uint8_t dc_plane_get_pipe_mask(struct dc_state *dc_stat= e, const struct dc_plane ************************************************************************= ******/ struct dc_plane_state *dc_create_plane_state(const struct dc *dc) { + printk(KERN_INFO "%s 0: preempt_count =3D %d\n", __func__, preempt= _count()); struct dc_plane_state *plane_state =3D kvzalloc_obj(*plane_state, GFP_ATOMIC); =20 Again I get only 0 for the preempt_count. Bert Karwatzki