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

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Date:   Tue, 21 Jul 2020 14:24:25 +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 14:09, Nicolas Saenz Julienne
<nsaenzjulienne@...e.de> wrote:
>
> Hi Amit,
>
> On Tue, 2020-07-21 at 12:51 +0530, Amit Pundir wrote:
> > On Wed, 8 Jul 2020 at 22:43, Nicolas Saenz Julienne
> > <nsaenzjulienne@...e.de> wrote:
> > > There is no guarantee to CMA's placement, so allocating a zone
> > > specific
> > > atomic pool from CMA might return memory from a completely
> > > different
> > > memory zone. So stop using it.
> > >
> > > Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to
> > > map to gfp mask")
> >
> > 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

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 ++---------
> > >  1 file changed, 2 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> > > index 8cfa01243ed2..4bc1c46ae6ef 100644
> > > --- a/kernel/dma/pool.c
> > > +++ b/kernel/dma/pool.c
> > > @@ -6,7 +6,6 @@
> > >  #include <linux/debugfs.h>
> > >  #include <linux/dma-direct.h>
> > >  #include <linux/dma-noncoherent.h>
> > > -#include <linux/dma-contiguous.h>
> > >  #include <linux/init.h>
> > >  #include <linux/genalloc.h>
> > >  #include <linux/set_memory.h>
> > > @@ -69,12 +68,7 @@ static int atomic_pool_expand(struct gen_pool
> > > *pool, size_t pool_size,
> > >
> > >         do {
> > >                 pool_size = 1 << (PAGE_SHIFT + order);
> > > -
> > > -               if (dev_get_cma_area(NULL))
> > > -                       page = dma_alloc_from_contiguous(NULL, 1 <<
> > > order,
> > > -                                                        order,
> > > false);
> > > -               else
> > > -                       page = alloc_pages(gfp, order);
> > > +               page = alloc_pages(gfp, order);
> > >         } while (!page && order-- > 0);
> > >         if (!page)
> > >                 goto out;
> > > @@ -118,8 +112,7 @@ static int atomic_pool_expand(struct gen_pool
> > > *pool, size_t pool_size,
> > >         dma_common_free_remap(addr, pool_size);
> > >  #endif
> > >  free_page: __maybe_unused
> > > -       if (!dma_release_from_contiguous(NULL, page, 1 << order))
> > > -               __free_pages(page, order);
> > > +       __free_pages(page, order);
> > >  out:
> > >         return ret;
> > >  }
> > > --
> > > 2.27.0
> > >
>