linux-kernel - Re: [PATCH] dma-pool: Do not allocate pool memory from CMA

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Date:   Tue, 21 Jul 2020 17:45:02 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        David Rientjes <rientjes@...gle.com>,
        linux-rpi-kernel@...ts.infradead.org, jeremy.linton@....com,
        iommu@...ts.linux-foundation.org,
        lkml <linux-kernel@...r.kernel.org>,
        John Stultz <john.stultz@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH] dma-pool: Do not allocate pool memory from CMA

On Tue, 21 Jul 2020 at 16:45, Nicolas Saenz Julienne
<nsaenzjulienne@...e.de> wrote:
>
> On Tue, 2020-07-21 at 14:24 +0530, Amit Pundir wrote:
> > On Tue, 21 Jul 2020 at 14:09, Nicolas Saenz Julienne
> > <nsaenzjulienne@...e.de> wrote:
> > > Hi Amit,
> > > > Hi Nicolas,
> > > >
> > > > I see a boot regression with this commit d9765e41d8e9 "dma-pool:
> > > > Do not allocate pool memory from CMA" on my Xiaomi Poco F1
> > > > (Qcom sdm845) phone running v5.8-rc6. I can't boot past the
> > > > bootloader splash screen with this patch.
> > > >
> > > > Phone boots fine if I revert this patch. I carry only one out of
> > > > tree
> > > > dts patch https://lkml.org/lkml/2020/6/25/52. And since this is a
> > > > stock
> > > > phone, I don't have access to serial/dmesg logs until I boot to
> > > > AOSP
> > > > (adb) shell.
> > > >
> > > > Any thoughts as to what might be going wrong here? I'd be happy
> > > > to
> > > > help debug things. For what it's worth, I don't see this
> > > > regression
> > > > on
> > > > other two sdm845 devices (db845c and Pixel 3) I tested on.
> > >
> > > Can you provide a boot log (even if without my patch) and the
> > > device-
> > > tree files? It'd help a lot figuring things out.
> >
> > Thank you for the prompt reply Nicolas.
> >
> > Here is the boot log with the reverted patch
> > https://pastebin.ubuntu.com/p/BrhPf83nKF/
> >
> > Here is my phone's dts
> > https://github.com/pundiramit/linux/commit/2a394c199deeaf4c91e0e008e8fba2a72f494d8c
>
> I'm at loss at what could be failing here. Your device should be able
> to address the whole 8GB memory space, which AFAIK is the max available
> on that smartphone family. But maybe the device-tree is lying, who
> knows...

If it helps, my phone has 6GB memory space.

>
> Can you try booting *without* my patch and this in the kernel command
> line: "cma=16M@...00000000-0x200000000".

It doesn't boot with this added kernel command line.

Regards,
Amit Pundir

>
> Regards,
> Nicolas
>
> And here is my kernel tree just in case
> > https://github.com/pundiramit/linux/commits/beryllium-mainline
> >
> > Regards,
> > Amit Pundir
> >
> >
> > > Regards,
> > > Nicolas
> > >
> > > > Regards,
> > > > Amit Pundir
> > > >
> > > > > Reported-by: Jeremy Linton <jeremy.linton@....com>
> > > > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > > > > ---
> > > > >
> > > > > An more costly alternative would be adding an option to
> > > > > dma_alloc_from_contiguous() so it fails when the allocation
> > > > > doesn't
> > > > > fall
> > > > > in a specific zone.
> > > > >
> > > > >  kernel/dma/pool.c | 11 ++---------
>