| Message ID | b65d009bf4aeb83b97e02a9fd03c14888b5f1ce2.1420843412.git.yann.morin.1998@free.fr |
|---|---|
| State | Changes Requested |
| Headers | show |
Dear Yann E. MORIN, On Fri, 9 Jan 2015 23:46:23 +0100, Yann E. MORIN wrote: > - we can not use the minimalist RPi defconfig bundled with the kernel, > namely bcmrpi_quick_defconfig, because it is not DT-enabled, and > sets CONFIG_ARM_PATCH_PHYS_VIRT to 'n', which prompts a value for > CONFIG_PHYS_OFFSET, as it as no default for the bcm familly; > > - we have to use the 'default' but bloated bcmrpi_defconfig, which > makes for a very fat kernel with lots of modules, and takes ages to > build; > > - most importantly, the rpi-3.18.y branch is constantly rebased, so > there is no guarantee that the sha1 I use today will still be usable > in the long term. Using the name of hte branch is not better either. Well, you could alternatively decide to have a custom kernel defconfig in board/raspberrypi/, which would be the same as bcmrpi_quick, with just the modifications you need for DT. Sure it means it will have to be updated from time to time, but hopefully at some point in the future the official bcmrpi_quick defconfig will have DT support enabled. Thomas
Hello, On Sat, 10 Jan 2015 12:17:51 +0100, Thomas Petazzoni wrote: > > - we can not use the minimalist RPi defconfig bundled with the kernel, > > namely bcmrpi_quick_defconfig, because it is not DT-enabled, and > > sets CONFIG_ARM_PATCH_PHYS_VIRT to 'n', which prompts a value for > > CONFIG_PHYS_OFFSET, as it as no default for the bcm familly; > > > > - we have to use the 'default' but bloated bcmrpi_defconfig, which > > makes for a very fat kernel with lots of modules, and takes ages to > > build; > > > > - most importantly, the rpi-3.18.y branch is constantly rebased, so > > there is no guarantee that the sha1 I use today will still be usable > > in the long term. Using the name of hte branch is not better either. > > Well, you could alternatively decide to have a custom kernel defconfig > in board/raspberrypi/, which would be the same as bcmrpi_quick, with > just the modifications you need for DT. Sure it means it will have to > be updated from time to time, but hopefully at some point in the future > the official bcmrpi_quick defconfig will have DT support enabled. Another motivation would be to switch back to an internal toolchain. Using an external toolchain here is quite inefficient: for an ARMv6 such as the RPi, we will fallback to the CodeSourcery toolchain, which will generate ARMv5 soft-float code. Not nice for a VFP-using ARMv6. Thomas
diff --git a/configs/raspberrypi_dt_defconfig b/configs/raspberrypi_dt_defconfig new file mode 100644 index 0000000..188ece9 --- /dev/null +++ b/configs/raspberrypi_dt_defconfig @@ -0,0 +1,12 @@ +BR2_arm=y +BR2_arm1176jzf_s=y +BR2_TOOLCHAIN_EXTERNAL=y +BR2_TARGET_GENERIC_GETTY_PORT="tty1" +BR2_LINUX_KERNEL=y +BR2_LINUX_KERNEL_CUSTOM_GIT=y +BR2_LINUX_KERNEL_CUSTOM_REPO_URL="git://github.com/raspberrypi/linux.git" +BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="b9c9f8fc69aaba236169798c18dc1590fccf7acd" +BR2_LINUX_KERNEL_DEFCONFIG="bcmrpi" +BR2_LINUX_KERNEL_ZIMAGE=y +BR2_PACKAGE_RPI_FIRMWARE=y +BR2_PACKAGE_RPI_FIRMWARE_INSTALL_DTBS=y
This is an example of a Device-Tree-enabled Raspberry Pi defconfig. We have to use a 3.18-based kernel for that, but there are a few limitations: - we can not use the minimalist RPi defconfig bundled with the kernel, namely bcmrpi_quick_defconfig, because it is not DT-enabled, and sets CONFIG_ARM_PATCH_PHYS_VIRT to 'n', which prompts a value for CONFIG_PHYS_OFFSET, as it as no default for the bcm familly; - we have to use the 'default' but bloated bcmrpi_defconfig, which makes for a very fat kernel with lots of modules, and takes ages to build; - most importantly, the rpi-3.18.y branch is constantly rebased, so there is no guarantee that the sha1 I use today will still be usable in the long term. Using the name of hte branch is not better either. To compensate for an already overly-long build time for such a minimalist system (18min 20s, as compared to 6min 30s when using bcmrpi_quick), I decided to use an external toolchain rather than build our own. Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr> --- configs/raspberrypi_dt_defconfig | 12 ++++++++++++ 1 file changed, 12 insertions(+) create mode 100644 configs/raspberrypi_dt_defconfig