ACK: [SRU][raspi2-eoan][PATCH 1/1] bcm2708_fb: Disable warning when calling dma_alloc_coherent

[Kleber Souza]

On 2019-12-11 08:15, Hui Wang wrote:
> BugLink: https://bugs.launchpad.net/bugs/1855990
> 
> When we boot the kernel on the rpi4/3/2, we sometimes could see the
> warning calltrace like below:
> 
> bcm2708_fb soc:fb: FB found 1 display(s)
> cma: cma_alloc: alloc failed, req-size: 1753 pages, ret: -12
> WARNING: CPU: 2 PID: 1 at mm/page_alloc.c:4702 __alloc_pages_nodemask+0x284/0x2c8
> Modules linked in:
> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.3.0-1013-raspi2 #15-Ubuntu
> Hardware name: Raspberry Pi 3 Model B Plus Rev 1.3 (DT)
> pstate: 20400005 (nzCv daif +PAN -UAO)
> pc : __alloc_pages_nodemask+0x284/0x2c8
> lr : __dma_direct_alloc_pages+0x100/0x1e8
> sp : ffff0000100238a0
> x29: ffff0000100238a0 x28: 0000000000000000
> x27: ffffa7c578867580 x26: ffffa7c57786a080
> ...
> 
> After investigation, I found there are two situations which could
> introduce this calltrace.
>  1) booting the arm64 kernel on rpi4 boards without the monitor
>  connected, in this situation, the xres and yres euqal to 0, so the
>  dma_alloc_coherent wants to alloc a memory region with 0 size, this
>  will result the get_order() returns (BITS_PER_LONG - PAGE_SHIFT),
>  then it will introduce the calltrace because
>  unlikely(order >= MAX_ORDER) is true (mm/page_alloc.c)
>  2) booting the kernel on rpi2/3 boards with a high resolution monitor
>  connected, in this case the xres * yres is too big, the cma_alloc
>  doens't have enough memory for it, and finally it will also introduce
>  the calltrace by unlikely(order >= MAX_ORDER) is true.
> 
> The bcm2708_fb could handle the situation of failure on calling
> dma_alloc_coherent, and the driver itself will print some log to
> notify users that this alloc fails. So we don't need the mm/page_alloc
> to print that calltrace anymore, printing a calltrace when booting
> usually makes users think the kernel has a critical problem.
> 
> Signed-off-by: Hui Wang <hui.wang at canonical.com>
> (cherry picked from commit 373a1ab55a8ef178fbe9f4d505c4714c3f7b3e9e
> https://github.com/raspberrypi/linux.git rpi-5.3.y)
> Signed-off-by: Hui Wang <hui.wang at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  drivers/video/fbdev/bcm2708_fb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/bcm2708_fb.c b/drivers/video/fbdev/bcm2708_fb.c
> index 59443f79f228..efbcc1f803bc 100644
> --- a/drivers/video/fbdev/bcm2708_fb.c
> +++ b/drivers/video/fbdev/bcm2708_fb.c
> @@ -410,7 +410,8 @@ static int bcm2708_fb_set_par(struct fb_info *info)
>  		}
>  
>  		fb->cpuaddr = dma_alloc_coherent(info->device, image_size,
> -						 &fb->dma_addr, GFP_KERNEL);
> +						 &fb->dma_addr,
> +						 GFP_KERNEL | __GFP_NOWARN);
>  
>  		if (!fb->cpuaddr) {
>  			fb->dma_addr = 0;
>