Re: [meta-raspberrypi][PATCH 0/5] Add support for 4.1 kernel with vc4 DRM/KMS driver

[Javier Martinez Canillas <javier@osg.samsung.com>]

Hello Petter,

Thanks a lot for your feedback.

On 08/04/2015 11:16 AM, Petter Mabäcker wrote:
> On 07/30/2015 10:34 AM, Javier Martinez Canillas wrote:
>> Hello Andrei,
>>
>> This series adds support for Eric Anholt's v4.1 kernel, that has support
>> for the vc4 DRM/KMS driver. Which is the new open source graphics driver
>> stack for the Raspberry Pi to be used instead of the userland driver.
>>
>> We are using it in the Tizen port to RPI2 [0] and are trying to push all
>> the patches back to the tizen-distro and meta-raspberrypi OE layers so
>> I'm posting these patches to get your feedback.
>>
>> The v4.1 kernel is under heavy development so is a work-in-progress and
>> should not be used in production. That's why a default preference of -1
>> is set and the kernel only is enabled if the "vc4-gfx" feature is added
>> to the DISTRO_FEATURES variable.
>>
>> But even when it's still a development kernel, having the recipe in the
>> meta-raspberrypi will allow people to test it. The patches are for:
>>
>> Patch 1/5 makes optional to add the kgdboc kernel command line parameter
>>
>> Patch 2/5 allows to set the mask_gpu_interrupt0 option in config.txt
>>
>> Patch 3/5 changes the partition layout to add more space for boot files
>>
>> Patch 4/5 adds a recipe for the 4.1 and some patches to make it stable
>>
>> Patch 5/5 switchs the default providers according to the gfx stack used
>>
>> One problem I found is that the latest RPI kernels changed the path for
>> the DT overlays after commit 739c586c8757 ("BCM270X_DT: Move the overlays
>> into a subdirectory, adding the README") [1] so the kernel fails to build
>> with the default KERNEL_DEVICETREE. I tried to change get_dts() function
>> logic to take this into account but found that it would had been a more
>> intrusive change and KERNEL_DEVICETREE will have to be changed anyways
>> once the recipes for the other kernels are updated to the latest HEAD so
>> for now I just define the following on local.conf to make it build:
> As long as we bump SRCREV for 3.18 kernel as well, I see no problem. Since then the KERNEL_DEVICETREE default value can look the same in all situations (both 3.18 and 4.x can handle the new structure and we get no compatibility issues) and for older kernels (3.12 and 3.14) it doesn't matter since they don't have native device tree support and will turn device tree support off by default.
>

Yes, that's what I meant when I said that the problem will be solved once
all the recipes for DT enabled kernels are updated to the latest branch
HEAD. But I didn't want to do that in this series since I wanted the
changes to be as less intrusive as possible.
 
>>
>> KERNEL_DEVICETREE = " \
>>      bcm2708-rpi-b.dtb \
>>      bcm2708-rpi-b-plus.dtb \
>>      bcm2709-rpi-2-b.dtb \
>>      \
>>      overlays/hifiberry-amp-overlay.dtb \
>>      overlays/hifiberry-dac-overlay.dtb \
>>      overlays/hifiberry-dacplus-overlay.dtb \
>>      overlays/hifiberry-digi-overlay.dtb \
>>      overlays/iqaudio-dac-overlay.dtb \
>>      overlays/iqaudio-dacplus-overlay.dtb \
>>      overlays/lirc-rpi-overlay.dtb \
>>      overlays/pps-gpio-overlay.dtb \
>>      overlays/w1-gpio-overlay.dtb \
>>      overlays/w1-gpio-pullup-overlay.dtb \
>>      "
>>
>> [0]: http://blogs.s-osg.org/tizen-rpi2-now-supporting-3d-acceleration/
>> [1]: https://github.com/raspberrypi/linux/commit/739c586c8757
>>
>> Best regards,
>> ---
>> Javier Martinez Canillas
>> Open Source Group
>> Samsung Research America
>>
>>
>> Derek Foreman (4):
>>    rpi-config: Allow to mask GPU irqs
>>    sdcard_image-rpi.bbclass: Allocate more space for boot partition
>>    linux-raspberrypi: Add a 4.1 linux kernel with vc4 support
>>    rpi-default-providers: Switch providers according to used gfx stack
>>
>> Mauro Carvalho Chehab (1):
>>    linux-raspberrypi.inc: Make kgdboc kernel param optional
>>
>>   README                                             |  38 +++++--
>>   classes/sdcard_image-rpi.bbclass                   |   6 +-
>>   conf/machine/include/rpi-default-providers.inc     |   8 +-
>>   conf/machine/include/rpi-default-versions.inc      |   2 +-
>>   recipes-bsp/bootfiles/rpi-config_git.bb            |   6 ++
>>   recipes-kernel/linux/linux-raspberrypi.inc         |   5 +-
>>   ..._defconfig-Enable-config-options-for-vc4-.patch |  48 +++++++++
>>   ...-ARM-dts-Fix-i2c-for-bcm2709-RPI2-B-board.patch |  85 +++++++++++++++
>>   .../0003-drm-vc4-Use-the-fbdev_cma-helpers.patch   | 115 +++++++++++++++++++++
>>   .../0004-drm-vc4-Allow-vblank-to-be-disabled.patch |  26 +++++
>>   .../0005-drm-vc4-Disable-KMS-operations.patch      |  95 +++++++++++++++++
>>   recipes-kernel/linux/linux-raspberrypi_4.1.bb      |  16 +++
>>   12 files changed, 433 insertions(+), 17 deletions(-)
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi/0001-ARM-bcm2709_defconfig-Enable-config-options-for-vc4-.patch
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi/0002-ARM-dts-Fix-i2c-for-bcm2709-RPI2-B-board.patch
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi/0003-drm-vc4-Use-the-fbdev_cma-helpers.patch
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi/0004-drm-vc4-Allow-vblank-to-be-disabled.patch
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi/0005-drm-vc4-Disable-KMS-operations.patch
>>   create mode 100644 recipes-kernel/linux/linux-raspberrypi_4.1.bb
>>
> 
> Nice and interesting changes, but you really should sync this with Alex Lennon as well since he currently are working with integrating 4.1 into meta-raspberrypi. An other opinion is that you should start by trying to integrate relevant kernel changes both from 'git://github.com/anholt/linux.git;protocol=git;branch=vc4-kms-v3d-rpi2' and the integration patches into the currently used upstream (https://github.com/raspberrypi/linux) and I also think it's a good idea to ensure that the new code is added within kernel config options so it's easy to enable/disable the vc4 support. Then at least I think this more easily can be integrated in meta-raspberrypi.
>

I didn't know there was a work in progress to integrate the 4.1 tree.
Although that is for the branch in https://github.com/raspberrypi/linux
that does not have the Broadcom VC4 DRM/KMS driver. I agree that ideally
Eric's changes should be integrated back to that tree but I don't expect
that to be a trivial task. I certainly don't know if have the bandwidth
to do it. Also, it is under heavy development so will be hard to track.

Another option is to have two recipes for 4.1, one for the raspberrypi
tree with userland and another one with the tree with the VC4 DRM/KMS
driver. Or use the same recipe but with a different SRC_URI for each case.

I tried to isolate all the VC4 support so is enabled and disable easily
using a config option.

> BR,
> Petter

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America