Hi, On 3/30/21 9:09 AM, Thomas Zimmermann wrote: > Hi > > Am 29.03.21 um 16:50 schrieb Hans de Goede: >> 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. > > I do as well. And when I boot with simpledrm + native driver it's flicker-free from what I can tell. But drm_mode_config_reset() is supposed to reset HW and software state. There could be some corner case where we'd have to clear the screen. For now, it should be fine. Sounds good, thanks. > BTW if you have the time I'd appreciate your review of the patchset. Sorry, but I'm burried under a whole pile of other work. So although I would like to help it is better to say no. 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@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@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@xxxxxxxxxxxxxx/ >>>>> [2] https://lore.kernel.org/dri-devel/1761762.3HQLrFs1K7@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 >>>>> >>>> >>> >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@xxxxxxxxxxxxxxxxxxxxx >> https://lists.freedesktop.org/mailman/listinfo/dri-devel >> > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
