[Letux-kernel] LetuxOS: kernel: letux-5.5-rc1

[H. Nikolaus Schaller]

> Am 12.12.2019 um 16:27 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
>> 
>> So I'll try again to disable CONFIG_ARCH_BCM && CONFIG_ARCH_BCM2835.
> 
> Yes, looks like I did a mistake with my initial attempt.

Even deeper analysis shows that CONFIG_ARCH_BCM=y doesn't break the kernel
but CONFIG_ARCH_BCM2835=y does.

Just adding the latter makes all kernel files recompile with e.g.

  CC      arch/arm/mach-omap2/omap_hwmod.o - due to: include/config/zone/dma.h include/generated/bounds.h

So I assume there is some SELECT in the Kconfig for CONFIG_ARCH_BCM2835
which changes a parameter in zone DMA (whatever this is) and/or bounds.

And that change is broken.

Here is the diff of setting CONFIG_ARCH_BCM2835=y:

iMac:master hns$ git diff | fgrep =y | egrep '^(\+|\-)'
+CONFIG_ZONE_DMA=y
+CONFIG_ARCH_BCM2835=y
+CONFIG_ARM_AMBA=y
+CONFIG_HW_RANDOM_BCM2835=y
+CONFIG_PINCTRL_BCM2835=y
+CONFIG_CLK_BCM2835=y
+CONFIG_BCM2835_TIMER=y
+CONFIG_ARM_TIMER_SP804=y
+CONFIG_BCM2835_POWER=y
+CONFIG_PL353_SMC=y
iMac:master hns$ 

There are indeed two CONFIGs which may affect ARM in general:

CONFIG_ZONE_DMA=y
CONFIG_ARM_AMBA=y

Either these subsystems are generally broken since v5.5-rc1
or OMAP and iMX6 have become incompatible.

Yes, they are automatically selected:

arch/arm/mach-bcm/Kconfig:
config ARCH_BCM2835
	bool "Broadcom BCM2835 family"
	depends on ARCH_MULTI_V6 || ARCH_MULTI_V7
	select GPIOLIB
	select ARM_AMBA
	select ARM_ERRATA_411920 if ARCH_MULTI_V6
	select ARM_GIC if ARCH_MULTI_V7
	select ZONE_DMA if ARCH_MULTI_V7
	select ARM_TIMER_SP804
	select HAVE_ARM_ARCH_TIMER if ARCH_MULTI_V7

and

arch/arm/mach-bcm/Kconfig:
config ARCH_BCM2835
	bool "Broadcom BCM2835 family"
	depends on ARCH_MULTI_V6 || ARCH_MULTI_V7
	select GPIOLIB
	select ARM_AMBA

Now let's consult git blame when they were introduced:

ARM_AMBA is old - since 2014.
But "select ZONE_DMA if ARCH_MULTI_V7" is new (Sept 2019):

781fa0a954240c8487683ddf837fb2c4ede8e7ca

So that may the issue, that OMAP doesn't like ZONE_DMA which
is force-set by ARCH_BCM2835?

BR,
Nikolaus