Re: [PATCHv2 00/56] drm/omap: Convert DSI code to use drm_mipi_dsi and drm_panel

[Sebastian Reichel <sre@kernel.org>]

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Hi,

On Wed, Feb 26, 2020 at 02:28:23PM +0200, Tomi Valkeinen wrote:
> On 25/02/2020 01:20, Sebastian Reichel wrote:
> > This updates the existing omapdrm DSI code, so that it uses
> > common drm_mipi_dsi API and drm_panel.
> > 
> > The patchset has been tested with Droid 4 using Linux console, X.org and
> > Weston. The patchset is based on Laurent Pinchartl's patch series [0]
> > and removes the last custom panel driver, so quite a few cleanups on the
> > omapdrm codebase were possible.
> 
> I haven't done any reviews yet, but applied these (and the one
> v2.1 patch) on top of Laurent's. I booted up AM5 EVM and loaded
> the modules:
> 
> [   17.261560] WARNING: CPU: 0 PID: 419 at drivers/base/component.c:636 component_bind_all+0x1f4/0x258

I did not see that warning for some reason. I guess I was always
lucky, since its a race condition introduced by "drm/omap: bind
components with drm_device argument". That patch moves
component_bind_all from dss_bind() to omapdrm's probe() to get
access to drm_dev. Currently omapdrm is the only DRM driver not
supplying that as parameter and its required to move encoder init
into the DSS output drivers. I assumed that it would be ok, since
it just postpones the call a little bit. Unfortunately it also
moves it out of the lock protection from dss_bind().

The only fix, that I see is to register the drm_dev is dss_bind
and then supply it to omapdrm via pdata. But I think we could
actually get rid of the omapdrm platform device completly and
just use its parent "omapdss_dss". I suppose a follow-up patchset
could merge the code into one module and do this merge.

Probably it's the best to drop that patch for now. It's not yet
used in the patches, that I sent.

> [   17.270811] Modules linked in: omapdrm(+) omapdss omapdss_base panel_osd_osd101t2587_53ts panel_simple simple_bridge ti_tpd12s015 display_connec
> tor tc358767 tc358768 sii902x ti_tfp410 drm_kms_helper drm drm_panel_orientation_quirks cfbfillrect cfbimgblt cfbcopyarea cec
> [   17.295521] CPU: 0 PID: 419 Comm: insmod Not tainted 5.6.0-rc2-00375-g66c4203ed9d4 #2
> [   17.303387] Hardware name: Generic DRA74X (Flattened Device Tree)
> [   17.309520] [<c011431c>] (unwind_backtrace) from [<c010dc20>] (show_stack+0x10/0x14)
> [   17.317306] [<c010dc20>] (show_stack) from [<c09acca4>] (dump_stack+0xb4/0xd0)
> [   17.324567] [<c09acca4>] (dump_stack) from [<c013a33c>] (__warn+0xc0/0xf8)
> [   17.331477] [<c013a33c>] (__warn) from [<c013a700>] (warn_slowpath_fmt+0x58/0xb8)
> [   17.338998] [<c013a700>] (warn_slowpath_fmt) from [<c0630698>] (component_bind_all+0x1f4/0x258)
> [   17.347768] [<c0630698>] (component_bind_all) from [<bf11b52c>] (pdev_probe+0xe0/0x7a0 [omapdrm])
> [   17.356709] [<bf11b52c>] (pdev_probe [omapdrm]) from [<c063a198>] (platform_drv_probe+0x48/0x98)
> [   17.365537] [<c063a198>] (platform_drv_probe) from [<c0637c1c>] (really_probe+0x200/0x478)
> [   17.373841] [<c0637c1c>] (really_probe) from [<c0638060>] (driver_probe_device+0x6c/0x1b4)
> [   17.382145] [<c0638060>] (driver_probe_device) from [<c06383f0>] (device_driver_attach+0x58/0x60)
> [   17.391060] [<c06383f0>] (device_driver_attach) from [<c063849c>] (__driver_attach+0xa4/0x148)
> [   17.399713] [<c063849c>] (__driver_attach) from [<c0635af8>] (bus_for_each_dev+0x70/0xb4)
> [   17.407930] [<c0635af8>] (bus_for_each_dev) from [<c0636d60>] (bus_add_driver+0x100/0x204)
> [   17.416233] [<c0636d60>] (bus_add_driver) from [<c0639078>] (driver_register+0x74/0x108)
> [   17.424361] [<c0639078>] (driver_register) from [<c063a2a8>] (__platform_register_drivers+0x58/0x150)
> [   17.433628] [<c063a2a8>] (__platform_register_drivers) from [<c0102ff8>] (do_one_initcall+0x48/0x2a0)
> [   17.442893] [<c0102ff8>] (do_one_initcall) from [<c01e2efc>] (do_init_module+0x5c/0x234)
> [   17.451022] [<c01e2efc>] (do_init_module) from [<c01e5668>] (load_module+0x250c/0x28a4)
> [   17.459064] [<c01e5668>] (load_module) from [<c01e5cb8>] (sys_finit_module+0xcc/0x110)
> [   17.467020] [<c01e5cb8>] (sys_finit_module) from [<c0101000>] (ret_fast_syscall+0x0/0x54)
> [   17.475233] Exception stack(0xea84bfa8 to 0xea84bff0)
> [   17.480307] bfa0:                   00000002 00000000 00000003 0002a894 00000000 bebd2d74
> [   17.488524] bfc0: 00000002 00000000 00028424 0000017b 0003eeb0 00000002 b6ffe000 00000000
> [   17.496738] bfe0: bebd2bb8 bebd2ba8 00020d7c b6edb0b0
> [   17.502365] ---[ end trace c20802296d6b2775 ]---
> [   17.508567] omapdss_dss 58000000.dss: bound 58001000.dispc (ops dsi_framedone_timeout_work_callback [omapdss])
> [   17.520358] omapdss_dss 58000000.dss: bound 58040000.encoder (ops dsi_framedone_timeout_work_callback [omapdss])
> [   17.559728] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [   17.574544] [drm] Enabling DMM ywrap scrolling
> [   17.580606] omapdrm omapdrm.0: fb0: omapdrmdrmfb frame buffer device
> [   17.625099] [drm] Initialized omapdrm 1.0.0 20110917 for omapdrm.0 on minor 0
> 
> Similar warning on module unload. The display works, though.

same problem, with dss_unbind() and omapdrm's remove function.

-- Sebastian

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