Thomas Zimmermann
2021-Mar-29 12:31 UTC
[PATCH v2 00/10] drm: Support simple-framebuffer devices and firmware fbs
Hi Am 25.03.21 um 12:29 schrieb Hans de Goede:> Hi, > > On 3/18/21 11:29 AM, Thomas Zimmermann wrote: >> This patchset adds support for simple-framebuffer platform devices and >> a handover mechanism for native drivers to take-over control of the >> hardware. >> >> The new driver, called simpledrm, binds to a simple-frambuffer platform >> device. The kernel's boot code creates such devices for firmware-provided >> framebuffers, such as EFI-GOP or VESA. Typically the BIOS, UEFI or boot >> loader sets up the framebuffers. Description via device tree is also an >> option. >> >> Simpledrm is small enough to be linked into the kernel. The driver's main >> purpose is to provide graphical output during the early phases of the boot >> process, before the native DRM drivers are available. Native drivers are >> typically loaded from an initrd ram disk. Occationally simpledrm can also >> serve as interim solution on graphics hardware without native DRM driver. >> >> So far distributions rely on fbdev drivers, such as efifb, vesafb or >> simplefb, for early-boot graphical output. However fbdev is deprecated and >> the drivers do not provide DRM interfaces for modern userspace. >> >> Patches 1 and 2 prepare the DRM format helpers for simpledrm. >> >> Patches 3 and 4 add a hand-over mechanism. Simpledrm acquires it's >> framebuffer's I/O-memory range and provides a callback function to be >> removed by a native driver. The native driver will remove simpledrm before >> taking over the hardware. The removal is integrated into existing helpers, >> so drivers use it automatically. >> >> Patches 5 to 10 add the simpledrm driver. It's build on simple DRM helpers >> and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB framebuffers. During >> pageflips, SHMEM buffers are copied into the framebuffer memory, similar >> to cirrus or mgag200. The code in patches 8 and 9 handles clocks and >> regulators. It's based on the simplefb drivers, but has been modified for >> DRM. > > Thank you for your work on this, this is very interesting. > >> I've also been working on fastboot support (i.e., flicker-free booting). >> This requires state-readout from simpledrm via generic interfaces, as >> outlined in [1]. I do have some prototype code, but it will take a while >> to get this ready. Simpledrm will then support it. >> >> I've tested simpledrm with x86 EFI and VESA framebuffers, which both work >> reliably. The fbdev console and Weston work automatically. Xorg requires >> manual configuration of the device. Xorgs current modesetting driver does >> not work with both, platform and PCI device, for the same physical >> hardware. Once configured, X11 works. I looked into X11, but couldn't see >> an easy way of fixing the problem. With the push towards Wayland+Xwayland >> I expect the problem to become a non-issue soon. Additional testing has >> been reported at [2]. >> >> One cosmetical issue is that simpledrm's device file is card0 and the >> native driver's device file is card1. After simpledrm has been kicked out, >> only card1 is left. This does not seem to be a practical problem however. >> >> TODO/IDEAS: >> >> * provide deferred takeover > > I'm not sure what you mean with this ? Currently deferred-takeover is > handled in the fbcon code. Current flickerfree boot works like this > (assuming a single LCD panel in a laptop): > > 1. EFI/GOP sets up the framebuffer, draws a vendor logo > 2. The bootloader runs in silent mode and does not touch anything gfx related > 3. kernel boots, with a loglevel of 3 so only CRIT/EMERG messages are shown > 2. efifb loads; and tells fbcon that a framebuffer is now available for it to "bind" > to. Since CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER=y fbcon defers taking over > the console and leaves the dummy-console driver in place (unless there have already > been kernel messages logged, which there shouldn't because loglevel=3) > 3. i915 loads, reads out the hw state compares this to the preferred-mode for the > panel which it would set, they match, nothing happens. i915 takes ownership > of the scanout-buffer set up by the GOP, but leaves it in place. > i915 also removes the efifb /dev/fb0 and installs its own /dev/fb0 fbdev compat > device, fbcon is notified of this, but is still deferred and leaves the dummy > console driver in place as console driver. > 4. Plymouth loads, allocates a new scan-out buffer at the panel's preferred resolution, > plymouth reads the vendor-logo through the BGRT ACPI interface and fills the > scanout-buffer with the vendor-logo + a spinner. Then plymouth installs the new > scanout-buffer on the crtc, this is done atomically during vsync, so the user > sees no changes, other then the spinner appearing > (note the active VT is now in graphical mode) > 5. From here on not flickering is a userspace problem > > AFAICT this should work fine with simplekms too, unless it clears the screen > to black when it binds.I forgot to add the code that clears the screen, but that's the case here. Instead of a plane-disable operation, simpledrm can at best clear the screen. This would happen during the initial mode-config reset IIRC. But we need to keep the display content stored in a framebuffer, so read-out helpers are required. There are more users of these read-out helpers. Adding them at some point probably makes sense. Other drivers might also want to read the initial config from simpledrm via read-out helpers. I think only i915 currently supports something like that ATM. Best regards Thomas> > An addition to the above sequence, if at any time either the kernel or userspace > prints a message to the console; and at that time a fbdev is registered then fbcon > will takeover as the console driver from the dummy driver and it will start drawing > to the registered fbdev (1), destroying the framebuffer contents. Also if any messages > where printend while no fbdev was registered, then fbcon will takeover the console > as soon as a fbdev gets registered. > > So since we already have deferred-takeover in the fbcon code, I wonder what you > mean when you are talking about "provide deferred takeover" for simplekms? > > Regards, > > Hans > > > 1) Except when the VT has been switched to GFX mode when this happens, then fbcon > will delay using the fbdev until the VT is switched back to text mode. > > > p.s. > > This has the interesting side effect then when logging into a desktop GUI session: > kernel -> plymouth -> gdm -> GNOME user session > > There never is any output to the text-console and fbcon never takes-over, so on > many Laptops running say Fedora workstation the fbcon code is actually unused > until the user manually switches to another virtual-console to log in in > text-mode: > > [hans at x1 ~]$ dmesg | grep -E 'fbcon|Console:|Truecolor' > [ 0.258904] Console: colour dummy device 80x25 > [ 1.274726] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 > [ 1.274768] fbcon: Deferring console take-over > [ 2.540894] fbcon: i915drmfb (fb0) is primary device > [ 2.540896] fbcon: Deferring console take-over > [hans at x1 ~]$ uptime > 12:29:39 up 4:19, 1 user, load average: 0.58, 0.75, 0.81 > > Look mom no fbcon > > > > >> * provide bootsplash DRM client >> * make simplekms usable with ARM-EFI fbs >> >> v2: >> * rename to simpledrm, aperture helpers >> * reorganized patches >> * use hotplug helpers for removal (Daniel) >> * added DT match tables (Rob) >> * use shadow-plane helpers >> * lots of minor cleanups >> >> [1] https://lore.kernel.org/dri-devel/CAKMK7uHtqHy_oz4W7F+hmp9iqp7W5Ra8CxPvJ=9BwmvfU-O0gg at mail.gmail.com/ >> [2] https://lore.kernel.org/dri-devel/1761762.3HQLrFs1K7 at nerdopolis/ >> >> Thomas Zimmermann (10): >> drm/format-helper: Pass destination pitch to drm_fb_memcpy_dstclip() >> drm/format-helper: Add blitter functions >> drm/aperture: Move fbdev conflict helpers into drm_aperture.h >> drm/aperture: Add infrastructure for aperture ownership >> drm: Add simpledrm driver >> drm/simpledrm: Add fbdev emulation >> drm/simpledrm: Initialize framebuffer data from device-tree node >> drm/simpledrm: Acquire clocks from DT device node >> drm/simpledrm: Acquire regulators from DT device node >> drm/simpledrm: Acquire memory aperture for framebuffer >> >> Documentation/gpu/drm-internals.rst | 12 + >> MAINTAINERS | 7 + >> drivers/gpu/drm/Kconfig | 7 + >> drivers/gpu/drm/Makefile | 1 + >> drivers/gpu/drm/drm_aperture.c | 287 ++++++++ >> drivers/gpu/drm/drm_format_helper.c | 96 ++- >> drivers/gpu/drm/mgag200/mgag200_mode.c | 2 +- >> drivers/gpu/drm/tiny/Kconfig | 17 + >> drivers/gpu/drm/tiny/Makefile | 1 + >> drivers/gpu/drm/tiny/cirrus.c | 2 +- >> drivers/gpu/drm/tiny/simpledrm.c | 932 +++++++++++++++++++++++++ >> include/drm/drm_aperture.h | 96 +++ >> include/drm/drm_fb_helper.h | 56 +- >> include/drm/drm_format_helper.h | 10 +- >> 14 files changed, 1466 insertions(+), 60 deletions(-) >> create mode 100644 drivers/gpu/drm/drm_aperture.c >> create mode 100644 drivers/gpu/drm/tiny/simpledrm.c >> create mode 100644 include/drm/drm_aperture.h >> >> -- >> 2.30.1 >> >-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 N?rnberg, Germany (HRB 36809, AG N?rnberg) Gesch?ftsf?hrer: Felix Imend?rffer -------------- next part -------------- A non-text attachment was scrubbed... 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Hans de Goede
2021-Mar-29 14:50 UTC
[PATCH v2 00/10] drm: Support simple-framebuffer devices and firmware fbs
Hi, On 3/29/21 2:31 PM, Thomas Zimmermann wrote:> Hi > > Am 25.03.21 um 12:29 schrieb Hans de Goede: >> Hi, >> >> On 3/18/21 11:29 AM, Thomas Zimmermann wrote: >>> This patchset adds support for simple-framebuffer platform devices and >>> a handover mechanism for native drivers to take-over control of the >>> hardware. >>> >>> The new driver, called simpledrm, binds to a simple-frambuffer platform >>> device. The kernel's boot code creates such devices for firmware-provided >>> framebuffers, such as EFI-GOP or VESA. Typically the BIOS, UEFI or boot >>> loader sets up the framebuffers. Description via device tree is also an >>> option. >>> >>> Simpledrm is small enough to be linked into the kernel. The driver's main >>> purpose is to provide graphical output during the early phases of the boot >>> process, before the native DRM drivers are available. Native drivers are >>> typically loaded from an initrd ram disk. Occationally simpledrm can also >>> serve as interim solution on graphics hardware without native DRM driver. >>> >>> So far distributions rely on fbdev drivers, such as efifb, vesafb or >>> simplefb, for early-boot graphical output. However fbdev is deprecated and >>> the drivers do not provide DRM interfaces for modern userspace. >>> >>> Patches 1 and 2 prepare the DRM format helpers for simpledrm. >>> >>> Patches 3 and 4 add a hand-over mechanism. Simpledrm acquires it's >>> framebuffer's I/O-memory range and provides a callback function to be >>> removed by a native driver. The native driver will remove simpledrm before >>> taking over the hardware. The removal is integrated into existing helpers, >>> so drivers use it automatically. >>> >>> Patches 5 to 10 add the simpledrm driver. It's build on simple DRM helpers >>> and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB framebuffers. During >>> pageflips, SHMEM buffers are copied into the framebuffer memory, similar >>> to cirrus or mgag200. The code in patches 8 and 9 handles clocks and >>> regulators. It's based on the simplefb drivers, but has been modified for >>> DRM. >> >> Thank you for your work on this, this is very interesting. >> >>> I've also been working on fastboot support (i.e., flicker-free booting). >>> This requires state-readout from simpledrm via generic interfaces, as >>> outlined in [1]. I do have some prototype code, but it will take a while >>> to get this ready. Simpledrm will then support it. >>> >>> I've tested simpledrm with x86 EFI and VESA framebuffers, which both work >>> reliably. The fbdev console and Weston work automatically. Xorg requires >>> manual configuration of the device. Xorgs current modesetting driver does >>> not work with both, platform and PCI device, for the same physical >>> hardware. Once configured, X11 works. I looked into X11, but couldn't see >>> an easy way of fixing the problem. With the push towards Wayland+Xwayland >>> I expect the problem to become a non-issue soon. Additional testing has >>> been reported at [2]. >>> >>> One cosmetical issue is that simpledrm's device file is card0 and the >>> native driver's device file is card1. After simpledrm has been kicked out, >>> only card1 is left. This does not seem to be a practical problem however. >>> >>> TODO/IDEAS: >>> >>> ????* provide deferred takeover >> >> I'm not sure what you mean with this ?? Currently deferred-takeover is >> handled in the fbcon code. Current flickerfree boot works like this >> (assuming a single LCD panel in a laptop): >> >> 1. EFI/GOP sets up the framebuffer, draws a vendor logo >> 2. The bootloader runs in silent mode and does not touch anything gfx related >> 3. kernel boots, with a loglevel of 3 so only CRIT/EMERG messages are shown >> 2. efifb loads; and tells fbcon that a framebuffer is now available for it to "bind" >> ??? to. Since CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER=y fbcon defers taking over >> ??? the console and leaves the dummy-console driver in place (unless there have already >> ??? been kernel messages logged, which there shouldn't because loglevel=3) >> 3. i915 loads, reads out the hw state compares this to the preferred-mode for the >> ??? panel which it would set, they match, nothing happens. i915 takes ownership >> ??? of the scanout-buffer set up by the GOP, but leaves it in place. >> ??? i915 also removes the efifb /dev/fb0 and installs its own /dev/fb0 fbdev compat >> ??? device, fbcon is notified of this, but is still deferred and leaves the dummy >> ??? console driver in place as console driver. >> 4. Plymouth loads, allocates a new scan-out buffer at the panel's preferred resolution, >> ??? plymouth reads the vendor-logo through the BGRT ACPI interface and fills the >> ??? scanout-buffer with the vendor-logo + a spinner. Then plymouth installs the new >> ??? scanout-buffer on the crtc, this is done atomically during vsync, so the user >> ??? sees no changes, other then the spinner appearing >> ??? (note the active VT is now in graphical mode) >> 5. From here on not flickering is a userspace problem >> >> AFAICT this should work fine with simplekms too, unless it clears the screen >> to black when it binds. > > I forgot to add the code that clears the screen, but that's the case here. > > Instead of a plane-disable operation, simpledrm can at best clear the screen. This would happen during the initial mode-config reset IIRC.Hmm, clearing the screen without any (atomic) modesets being initiated by either an in kernel drm-client or userspace seems wrong, this is certainly different from what the i915 driver does. The way I see it either a drm client provides a new framebuffer in which case you copy that over the old contents, effectively clearing it. Or a drm-client gets a handle and draws to the current fb directly, in which case it is the clients responsibility to clear it itself first. IOW I believe that simpledrm should not clear the screen itself at all. Regards, Hans> But we need to keep the display content stored in a framebuffer, so read-out helpers are required. There are more users of these read-out helpers. Adding them at some point probably makes sense. > > Other drivers might also want to read the initial config from simpledrm via read-out helpers. I think only i915 currently supports something like that ATM. > > Best regards > Thomas > >> >> An addition to the above sequence, if at any time either the kernel or userspace >> prints a message to the console; and at that time a fbdev is registered then fbcon >> will takeover as the console driver from the dummy driver and it will start drawing >> to the registered fbdev (1), destroying the framebuffer contents. Also if any messages >> where printend while no fbdev was registered, then fbcon will takeover the console >> as soon as a fbdev gets registered. >> >> So since we already have deferred-takeover in the fbcon code, I wonder what you >> mean when you are talking about "provide deferred takeover" for simplekms? >> >> Regards, >> >> Hans >> >> >> 1) Except when the VT has been switched to GFX mode when this happens, then fbcon >> will delay using the fbdev until the VT is switched back to text mode. >> >> >> p.s. >> >> This has the interesting side effect then when logging into a desktop GUI session: >> kernel -> plymouth -> gdm -> GNOME user session >> >> There never is any output to the text-console and fbcon never takes-over, so on >> many Laptops running say Fedora workstation the fbcon code is actually unused >> until the user manually switches to another virtual-console to log in in >> text-mode: >> >> [hans at x1 ~]$ dmesg | grep -E 'fbcon|Console:|Truecolor' >> [??? 0.258904] Console: colour dummy device 80x25 >> [??? 1.274726] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 >> [??? 1.274768] fbcon: Deferring console take-over >> [??? 2.540894] fbcon: i915drmfb (fb0) is primary device >> [??? 2.540896] fbcon: Deferring console take-over >> [hans at x1 ~]$ uptime >> ? 12:29:39 up? 4:19,? 1 user,? load average: 0.58, 0.75, 0.81 >> >> Look mom no fbcon >> >> >> >> >>> ????* provide bootsplash DRM client >>> ????* make simplekms usable with ARM-EFI fbs >>> >>> v2: >>> ????* rename to simpledrm, aperture helpers >>> ????* reorganized patches >>> ????* use hotplug helpers for removal (Daniel) >>> ????* added DT match tables (Rob) >>> ????* use shadow-plane helpers >>> ????* lots of minor cleanups >>> >>> [1] https://lore.kernel.org/dri-devel/CAKMK7uHtqHy_oz4W7F+hmp9iqp7W5Ra8CxPvJ=9BwmvfU-O0gg at mail.gmail.com/ >>> [2] https://lore.kernel.org/dri-devel/1761762.3HQLrFs1K7 at nerdopolis/ >>> >>> Thomas Zimmermann (10): >>> ?? drm/format-helper: Pass destination pitch to drm_fb_memcpy_dstclip() >>> ?? drm/format-helper: Add blitter functions >>> ?? drm/aperture: Move fbdev conflict helpers into drm_aperture.h >>> ?? drm/aperture: Add infrastructure for aperture ownership >>> ?? drm: Add simpledrm driver >>> ?? drm/simpledrm: Add fbdev emulation >>> ?? drm/simpledrm: Initialize framebuffer data from device-tree node >>> ?? drm/simpledrm: Acquire clocks from DT device node >>> ?? drm/simpledrm: Acquire regulators from DT device node >>> ?? drm/simpledrm: Acquire memory aperture for framebuffer >>> >>> ? Documentation/gpu/drm-internals.rst??? |? 12 + >>> ? MAINTAINERS??????????????????????????? |?? 7 + >>> ? drivers/gpu/drm/Kconfig??????????????? |?? 7 + >>> ? drivers/gpu/drm/Makefile?????????????? |?? 1 + >>> ? drivers/gpu/drm/drm_aperture.c???????? | 287 ++++++++ >>> ? drivers/gpu/drm/drm_format_helper.c??? |? 96 ++- >>> ? drivers/gpu/drm/mgag200/mgag200_mode.c |?? 2 +- >>> ? drivers/gpu/drm/tiny/Kconfig?????????? |? 17 + >>> ? drivers/gpu/drm/tiny/Makefile????????? |?? 1 + >>> ? drivers/gpu/drm/tiny/cirrus.c????????? |?? 2 +- >>> ? drivers/gpu/drm/tiny/simpledrm.c?????? | 932 +++++++++++++++++++++++++ >>> ? include/drm/drm_aperture.h???????????? |? 96 +++ >>> ? include/drm/drm_fb_helper.h??????????? |? 56 +- >>> ? include/drm/drm_format_helper.h??????? |? 10 +- >>> ? 14 files changed, 1466 insertions(+), 60 deletions(-) >>> ? create mode 100644 drivers/gpu/drm/drm_aperture.c >>> ? create mode 100644 drivers/gpu/drm/tiny/simpledrm.c >>> ? create mode 100644 include/drm/drm_aperture.h >>> >>> -- >>> 2.30.1 >>> >> >