[PATCH] arm64: cache: Lower ARCH_DMA_MINALIGN to 64 (L1_CACHE_BYTES)

[Marek Szyprowski]

Hi Mark,

On 04.06.2021 12:01, Mark Rutland wrote:
> On Wed, Jun 02, 2021 at 04:09:19PM +0200, Marek Szyprowski wrote:
>> On 02.06.2021 15:51, Mark Rutland wrote:
>>> On Wed, Jun 02, 2021 at 03:25:41PM +0200, Marek Szyprowski wrote:
>>>> On 27.05.2021 14:43, Will Deacon wrote:
>>>> This patch landed in todays linux-next as commit 65688d2a05de ("arm64:
>>>> cache: Lower ARCH_DMA_MINALIGN to 64 (L1_CACHE_BYTES)"). It causes an
>>>> issue on Raspberry Pi 3b board. System boots to userspace fine, but then
>>>> it hangs somewhere during the init scripts after loading the modules. I
>>>> didn't manage to track where it hangs yet though.
>>> Ouch!
>>>
>>> I have a 3b in a drawer that I might be able to reproduce the issue
>>> with; can you tell me how you're booting that kernel? e.g. which FW and
>>> DT you're using?
>> I'm booting the kernel with the mainline dtb
>> (arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dtb) from the u-boot,
>> which downloads it via TFTP. I don't remember which firmware version is
>> there, but without raspberry specific tools (which I don't have deployed
>> there) it is hard to check that now.
> Thanks, this was enough info to get started.
>
> For comparison, I have a 3Bv1.2 board.
>
> I grabbed the latest RPI firmware, built myself a v2021.07-rc3
> rpi_3_defconfig u-boot, and got a kernel booting (off the SD card rather
> than over the network).
>
> For the kernel I'm testing commit 65688d2a05de; defconfig with DRM and
> VC4 built-in, since passing modules around is painful in my setup.
>
>> The rootfs is on SD card, the system is some older Debian release.
> For comparison, I built myself a buildroot 2021.02.2 filesystem.
>
> So far, booting up an running I'm not seeeing issues (and no complaints
> from KASAN or similar), but I don't have a good way to stress the VC4
> GPU, so I might not be triggering whatever's going wrong.
>
> >From the log below I see the last message is about X sockets -- is the
> lockup happening when the display manager starts?

I've just checked with the latest firmware from 
https://github.com/raspberrypi/firmware (master branch, just copied 
everything to /boot) and the issue is still there.

If you start from arm64/defconfig without modules, please make sure you 
have enabled all RPi drivers, otherwise VC4 DRM won't come up. I've 
managed to reproduce the issue without the modules with the following 
changes to arm64's defconfig:

./scripts/config -e DRM -e DRM_VC4 -e CONFIG_CLK_RASPBERRYPI -e 
CONFIG_SENSORS_RASPBERRYPI_HWMON -e CONFIG_I2C_BCM2835 -e 
CONFIG_ARM_RASPBERRYPI_CPUFREQ

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland