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

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Message-ID: <011994f8a717a00dcd9ed7682a1ddeb421c2c43f.camel@suse.de>
Date:   Tue, 21 Jul 2020 13:15:23 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Amit Pundir <amit.pundir@...aro.org>
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, 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...

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

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 ++---------