talos-obmc-linux/include/linux/vga_switcheroo.h, branch v4.6

vga_switcheroo: Add support for switching only the DDC

2016-02-09T10:21:07+00:00

Originally by Seth Forshee , 2012-10-04: During graphics driver initialization it's useful to be able to mux only the DDC to the inactive client in order to read the EDID. Add a switch_ddc callback to allow capable handlers to provide this functionality, and add vga_switcheroo_switch_ddc() to allow DRM to mux only the DDC. Modified by Dave Airlie , 2012-12-22: I can't figure out why I didn't like this, but I rewrote this [...] to lock/unlock the ddc lines [...]. I think I'd prefer something like that otherwise the interface got really ugly. Modified by Lukas Wunner , 2015-04 - 2015-10: Change semantics of ->switch_ddc handler callback to return previous DDC owner. Original version tried to determine previous DDC owner with find_active_client() but this fails if the inactive client registers before the active client. Don't lock vgasr_mutex in _lock_ddc() / _unlock_ddc(), it can cause deadlocks because (a) during switch (with vgasr_mutex already held), GPU is woken and probes its outputs, tries to re-acquire vgasr_mutex to lock DDC lines; (b) Likewise during switch, GPU is suspended and calls cancel_delayed_work_sync() to stop output polling, if poll task is running at this moment we may wait forever for it to finish. Instead, lock mux_hw_lock when unregistering the handler because the only reason why we'd want to lock vgasr_mutex in _lock_ddc() / _unlock_ddc() is to block the handler from disappearing while DDC lines are switched. Also acquire mux_hw_lock in stage2 to avoid race condition where reading the EDID and switching happens simultaneously. Likewise on MIGD / MDIS commands and on runtime suspend. v2.1: Overhaul locking, squash commits (Daniel Vetter) v2.2: Readability improvements (Thierry Reding) v2.3: Overhaul locking once more v2.4: Retain semantics of ->switchto handler callback to switch all pins, including DDC (Daniel Vetter) v5: Rename ddc_lock to mux_hw_lock: Since we acquire this both when calling ->switch_ddc and ->switchto, it protects not just access to the DDC lines but to the mux in general. This is in line with the DRM convention to use low-level locks to avoid concurrent hw access (e.g. i2c, dp_aux) which are often called hw_lock (Daniel Vetter) Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88861 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61115 Tested-by: Lukas Wunner [MBP 9,1 2012 intel IVB + nvidia GK107 pre-retina 15"] Cc: Seth Forshee Cc: Dave Airlie Signed-off-by: Lukas Wunner Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/e81ae9722b84c5ed591805fee3ea6dbf5dc6c4b3.1452525860.git.lukas@wunner.de

vga_switcheroo: Add handler flags infrastructure

2016-02-09T10:21:07+00:00

Allow handlers to declare their capabilities and allow clients to obtain that information. So far we have these use cases: * If the handler is able to switch DDC separately, clients need to probe EDID with drm_get_edid_switcheroo(). We should allow them to detect a capable handler to ensure this function only gets called when needed. * Likewise if the handler is unable to switch AUX separately, the active client needs to communicate link training parameters to the inactive client, which may then skip the AUX handshake and set up its output with these pre-calibrated values (DisplayPort specification v1.1a, section 2.5.3.3). Clients need a way to recognize such a situation. The flags for the radeon_atpx_handler and amdgpu_atpx_handler are initially set to 0, this can later on be amended with handler_flags |= VGA_SWITCHEROO_CAN_SWITCH_DDC; when a ->switch_ddc callback is added. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88861 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61115 Tested-by: Lukas Wunner [MBP 9,1 2012 intel IVB + nvidia GK107 pre-retina 15"] Signed-off-by: Lukas Wunner Reviewed-by: Darren Hart Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/2b0d93ed6e511ca09e95e45e0b35627f330fabce.1452525860.git.lukas@wunner.de

vga_switcheroo: Drop client power state VGA_SWITCHEROO_INIT

2015-11-05T01:07:36+00:00

hda_intel.c:azx_probe() defers initialization of an audio controller on the discrete GPU if the GPU is powered off. The power state of the GPU is determined by calling vga_switcheroo_get_client_state(). vga_switcheroo_get_client_state() returns VGA_SWITCHEROO_INIT if vga_switcheroo is not enabled, i.e. if no second GPU or no handler has registered. This can go wrong in the following scenario: - Driver for the integrated GPU is not loaded. - Driver for the discrete GPU registers with vga_switcheroo, uses driver power control to power down the GPU, handler cuts power to the GPU. - Driver for the audio controller gets loaded after the GPU was powered down, calls vga_switcheroo_get_client_state() which returns VGA_SWITCHEROO_INIT instead of VGA_SWITCHEROO_OFF. - Consequence: azx_probe() tries to initialize the audio controller even though the GPU is powered down. The power state VGA_SWITCHEROO_INIT was introduced by c8e9cf7bb240 ("vga_switcheroo: Add a helper function to get the client state"). It is not apparent what its benefit might be. The idea seems to be to initialize the audio controller even if the power state is VGA_SWITCHEROO_OFF (were vga_switcheroo enabled), but as shown above this can fail. Drop VGA_SWITCHEROO_INIT to solve this. Acked-by: Takashi Iwai Signed-off-by: Lukas Wunner Signed-off-by: Dave Airlie

vga_switcheroo: Constify vga_switcheroo_handler

2015-10-20T18:19:29+00:00

vga_switcheroo_client_ops has always been declared const since its introduction with 26ec685ff9d9 ("vga_switcheroo: Introduce struct vga_switcheroo_client_ops"). Do so for vga_switcheroo_handler as well. drivers/gpu/drm/amd/amdgpu/amdgpu.ko: 6 .rodata 00009888 - 19 .data 00001f00 + 19 .data 00001ee0 drivers/gpu/drm/nouveau/nouveau.ko: 6 .rodata 000460b8 17 .data 00018fe0 drivers/gpu/drm/radeon/radeon.ko: - 7 .rodata 00030944 + 7 .rodata 00030964 - 21 .data 0000d6a0 + 21 .data 0000d678 drivers/platform/x86/apple-gmux.ko: - 7 .rodata 00000140 + 7 .rodata 00000160 - 11 .data 000000e0 + 11 .data 000000b8 Cc: Ben Skeggs Cc: Darren Hart Cc: Alex Deucher Signed-off-by: Lukas Wunner Reviewed-by: Christian König . Signed-off-by: Daniel Vetter

vga_switcheroo: Use enum vga_switcheroo_client_id instead of int

2015-10-16T13:50:56+00:00

Signed-off-by: Lukas Wunner Reviewed-by: Alex Deucher Signed-off-by: Daniel Vetter

vga_switcheroo: Use VGA_SWITCHEROO_UNKNOWN_ID instead of -1

2015-10-16T13:50:56+00:00

Signed-off-by: Lukas Wunner Reviewed-by: Alex Deucher Signed-off-by: Daniel Vetter

vga_switcheroo: Use enum vga_switcheroo_state instead of int

2015-10-16T13:50:55+00:00

Signed-off-by: Lukas Wunner Reviewed-by: Jani Nikula Reviewed-by: Alex Deucher Signed-off-by: Daniel Vetter

vga_switcheroo: Set active attribute to false for audio clients

2015-09-24T18:14:25+00:00

The active attribute in struct vga_switcheroo_client denotes whether the outputs are currently switched to this client. The attribute is only meaningful for vga clients. It is never used for audio clients. The function vga_switcheroo_register_audio_client() misuses this attribute to store whether the audio device is fully initialized. Most likely there was a misunderstanding about the meaning of "active" when this was added. Comment from Takashi's review: "Not really. The full initialization of audio was meant that the audio is active indeed. Admittedly, though, the active flag for each audio client doesn't play any role because the audio always follows the gfx state changes, and the value passed there doesn't reflect the actual state due to the later change. So, I agree with the removal of the flag itself -- or let the audio active flag following the corresponding gfx flag. The latter will make the proc output more consistent while the former is certainly more reduction of code." Set the active attribute to false for audio clients. Remove the active parameter from vga_switcheroo_register_audio_client() and its sole caller, hda_intel.c:register_vga_switcheroo(). vga_switcheroo_register_audio_client() was introduced by 3e9e63dbd374 ("vga_switcheroo: Add the support for audio clients"). Its use in hda_intel.c was introduced by a82d51ed24bb ("ALSA: hda - Support VGA-switcheroo"). v1.1: The changes above imply that in find_active_client() the call to client_is_vga() is now superfluous. Drop it. Cc: Takashi Iwai Signed-off-by: Lukas Wunner [danvet: Add Takashi's clarification to the commit message.] Reviewed-by: Takashi Iwai Signed-off-by: Daniel Vetter

vga_switcheroo: Document _ALL_ the things!

2015-09-22T08:37:26+00:00

This adds an "Overview" DOC section plus two DOC sections for the modes of use ("Manual switching and manual power control" and "Driver power control"). Also included is kernel-doc for all public functions, structs and enums. Signed-off-by: Lukas Wunner Signed-off-by: Daniel Vetter

vgaswitcheroo: add vga_switcheroo_fini_domain_pm_ops

2014-09-18T23:21:20+00:00

Drivers should call this on unload to unregister pmops. Bug: https://bugzilla.kernel.org/show_bug.cgi?id=84431 Reviewed-by: Ben Skeggs Signed-off-by: Alex Deucher Cc: stable@vger.kernel.org Signed-off-by: Pali Rohár Cc: Ben Skeggs