Hi Tomi, Am Freitag, 21. Juli 2023, 17:01:39 CEST schrieb Tomi Valkeinen: > DRM bridges are not visible to the userspace and it may not be > immediately clear if the chain is somehow constructed incorrectly. I > have had two separate instances of a bridge driver failing to do a > drm_bridge_attach() call, resulting in the bridge connector not being > part of the chain. In some situations this doesn't seem to cause issues, > but it will if DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is used. > > Add a debugfs file to print the bridge chains. For me, on this TI AM62 > based platform, I get the following output: > > encoder[39] > bridge[0] type: 0, ops: 0x0 > bridge[1] type: 0, ops: 0x0, OF: > /bus@f0000/i2c@20000000/dsi@e:toshiba,tc358778 bridge[2] type: 0, ops: 0x3, > OF: /bus@f0000/i2c@20010000/hdmi@48:lontium,lt8912b bridge[3] type: 11, > ops: 0x7, OF: /hdmi-connector:hdmi-connector I like the idea and it works on an imx8mp based board for the DRI display devices which have connectors attached: $ cat /sys/kernel/debug/dri/1/bridge_chains encoder[36] bridge[0] type: 16, ops: 0x0, OF: /soc@0/bus@32c00000/ dsi@32e60000:fsl,imx8mp-mipi-dsim bridge[1] type: 10, ops: 0x3, OF: /soc@0/bus@30800000/i2c@30a30000/ bridge@f:toshiba,tc9595 $ cat /sys/kernel/debug/dri/2/bridge_chains encoder[36] bridge[0] type: 0, ops: 0x0, OF: /soc@0/bus@32c00000/display- bridge@32fc4000:fsl,imx8mp-hdmi-pvi bridge[1] type: 0, ops: 0x7, OF: /soc@0/bus@32c00000/ hdmi@32fd8000:fsl,imx8mp-hdmi Unfortunately this oopses on GPU device without connectors: $ cat /sys/kernel/debug/dri/0/name etnaviv dev=etnaviv unique=etnaviv $ cat /sys/kernel/debug/dri/0/bridge_chains Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=0000000045842000 [0000000000000010] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP Modules linked in: dw_hdmi_cec mcp320x hantro_vpu snd_soc_fsl_asoc_card snd_soc_fsl_sai snd_soc_tlv320aic32x4_i2c snd_soc_imx_audmux snd_soc_fsl_utils snd_soc_tlv320aic32x4 snd_soc_simple_card_utils imx_pcm_dma snd_soc_core dw100 v4l2_vp9 8021q snd_pcm_dmaengine v4l2_h264 snd_pcm videobuf2_dma_contig garp imx8mp_hdmi crct10dif_ce v4l2_mem2mem mrp dw_hdmi tc358767 videobuf2_memops stp bluetooth llc synopsys_edac videobuf2_v4l2 cec videobuf2_common phy_fsl_samsung_hdmi imx8mp_hdmi_pvi samsung_dsim snd_timer cfg80211 snd flexcan drm_display_helper imx_sdma soundcore virt_dma can_dev clk_renesas_pcie coresight_etm4x coresight_tmc coresight_funnel pwm_imx27 coresight imx8mm_thermal iio_hwmon fuse ipv6 CPU: 3 PID: 485 Comm: cat Not tainted 6.5.0-rc3-next-20230724+ #1822 41dd31be02d36f174370d905469174492535c29d Hardware name: TQ-Systems i.MX8MPlus TQMa8MPxL on MBa8MPxL (DT) pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : drm_bridge_chains_info+0xfc/0x1d0 lr : drm_bridge_chains_info+0xf8/0x1d0 sp : ffff8000831c39e0 x29: ffff8000831c39e0 x28: ffff8000811759f0 x27: ffff800081175a08 x26: ffff800081175000 x25: ffff000002d592b0 x24: ffff000002d59000 x23: ffff800081175a70 x22: ffff800081175a50 x21: fffffffffffffff8 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 3836613136616661 x12: 3030303030303030 x11: 203a7473696c5f72 x10: 65646f636e65205d x9 : 6c5f7265646f636e x8 : 65205d6d72645b20 x7 : 0000000000000003 x6 : ffff8000818627a0 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff8000831c3a68 Call trace: drm_bridge_chains_info+0xfc/0x1d0 seq_read_iter+0x1a8/0x484 seq_read+0x88/0xbc full_proxy_read+0x5c/0xa8 vfs_read+0xac/0x1e0 ksys_read+0x68/0xf4 __arm64_sys_read+0x18/0x20 invoke_syscall+0x6c/0xec el0_svc_common.constprop.0+0xb8/0xd8 do_el0_svc+0x28/0x34 el0_svc+0x1c/0x50 el0t_64_sync_handler+0xb8/0xbc el0t_64_sync+0x14c/0x150 Code: aa1903e2 f94037e1 9401d66f 910223e0 (b9401aa2) ---[ end trace 0000000000000000 ]--- This boils down to the connector_list setup incorrectly? Here is some debug output from drm_bridge_chains_info: > etnaviv etnaviv: [drm] encoder_list: 00000000afa61a68 > etnaviv etnaviv: [drm] num_encoder: 0 > etnaviv etnaviv: [drm] list_empty: 0 > etnaviv etnaviv: [drm] encoder: fffffffffffffff8 > etnaviv etnaviv: [drm] encoder->head: 0000000000000000 list_empty(&config->encoder_list)) not returning true and num_encoder being 0 seems off to me. Best regards, Alexander > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx> > --- > Changes in v2: > - Fixed compilation issue when !CONFIG_OF > - Link to v1: > https://lore.kernel.org/r/20230721-drm-bridge-chain-debugfs-v1-1-8614ff7e89 > 0d@xxxxxxxxxxxxxxxx --- > drivers/gpu/drm/drm_bridge.c | 50 > +++++++++++++++++++++++++++++++++++++++++++ drivers/gpu/drm/drm_debugfs.c | > 3 +++ > include/drm/drm_bridge.h | 5 +++++ > 3 files changed, 58 insertions(+) > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index c3d69af02e79..d3eb62d5ef3b 100644 > --- a/drivers/gpu/drm/drm_bridge.c > +++ b/drivers/gpu/drm/drm_bridge.c > @@ -27,8 +27,10 @@ > #include <linux/mutex.h> > > #include <drm/drm_atomic_state_helper.h> > +#include <drm/drm_debugfs.h> > #include <drm/drm_bridge.h> > #include <drm/drm_encoder.h> > +#include <drm/drm_file.h> > #include <drm/drm_of.h> > #include <drm/drm_print.h> > > @@ -1345,6 +1347,54 @@ struct drm_bridge *of_drm_find_bridge(struct > device_node *np) EXPORT_SYMBOL(of_drm_find_bridge); > #endif > > +#ifdef CONFIG_DEBUG_FS > +static int drm_bridge_chains_info(struct seq_file *m, void *data) > +{ > + struct drm_debugfs_entry *entry = m->private; > + struct drm_device *dev = entry->dev; > + struct drm_printer p = drm_seq_file_printer(m); > + struct drm_mode_config *config = &dev->mode_config; > + struct drm_encoder *encoder; > + unsigned int bridge_idx = 0; > + > + list_for_each_entry(encoder, &config->encoder_list, head) { > + struct drm_bridge *bridge; > + > + drm_printf(&p, "encoder[%u]\n", encoder->base.id); > + > + bridge = drm_bridge_chain_get_first_bridge(encoder); > + > + while (bridge) { > + drm_printf(&p, "\tbridge[%u] type: %u, ops: %#x", > + bridge_idx, bridge->type, bridge- >ops); > + > +#ifdef CONFIG_OF > + if (bridge->of_node) > + drm_printf(&p, ", OF: %pOFfc", bridge- >of_node); > +#endif > + > + drm_printf(&p, "\n"); > + > + bridge_idx++; > + bridge = drm_bridge_get_next_bridge(bridge); > + } > + } > + > + return 0; > +} > + > +/* any use in debugfs files to dump individual planes/crtc/etc? */ > +static const struct drm_debugfs_info drm_bridge_debugfs_list[] = { > + {"bridge_chains", drm_bridge_chains_info, 0}, > +}; > + > +void drm_bridge_debugfs_init(struct drm_minor *minor) > +{ > + drm_debugfs_add_files(minor->dev, drm_bridge_debugfs_list, > + ARRAY_SIZE(drm_bridge_debugfs_list)); > +} > +#endif > + > MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@xxxxxxxxxxx>"); > MODULE_DESCRIPTION("DRM bridge infrastructure"); > MODULE_LICENSE("GPL and additional rights"); > diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c > index c90dbcffa0dc..3e89559d68cd 100644 > --- a/drivers/gpu/drm/drm_debugfs.c > +++ b/drivers/gpu/drm/drm_debugfs.c > @@ -31,6 +31,7 @@ > > #include <drm/drm_atomic.h> > #include <drm/drm_auth.h> > +#include <drm/drm_bridge.h> > #include <drm/drm_client.h> > #include <drm/drm_debugfs.h> > #include <drm/drm_device.h> > @@ -272,6 +273,8 @@ int drm_debugfs_init(struct drm_minor *minor, int > minor_id, > > drm_debugfs_add_files(minor->dev, drm_debugfs_list, DRM_DEBUGFS_ENTRIES); > > + drm_bridge_debugfs_init(minor); > + > if (drm_drv_uses_atomic_modeset(dev)) { > drm_atomic_debugfs_init(minor); > } > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h > index bf964cdfb330..60dbee6bd1e6 100644 > --- a/include/drm/drm_bridge.h > +++ b/include/drm/drm_bridge.h > @@ -949,4 +949,9 @@ static inline struct drm_bridge > *drmm_of_get_bridge(struct drm_device *drm, } > #endif > > +#ifdef CONFIG_DEBUG_FS > +struct drm_minor; > +void drm_bridge_debugfs_init(struct drm_minor *minor); > +#endif > + > #endif > > --- > base-commit: c7a472297169156252a50d76965eb36b081186e2 > change-id: 20230721-drm-bridge-chain-debugfs-0bbc1522f57a > > Best regards, -- TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht München, HRB 105018 Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider http://www.tq-group.com/