[fedora-arm] [PATCH] Bump CMA to 64M by default as found in 3.15 multi_v7_defconfig

[Peter Robinson]

NACK. See https://bugzilla.redhat.com/show_bug.cgi?id=1127000 for details.

Peter


On Mon, Aug 4, 2014 at 7:56 PM, Nicolas Chauvet <kwizart at gmail.com> wrote:
> The commit d1c912c1001f was made into tegra_defconfig and later
> forwared to multi_v7_deconfig as 0c86f089e66a93
>
> Quoting original commit into the kernel tree:
> - Allocate 64 MiB for CMA by default; the default 16MiB is not enough
>   for the majority of use-cases. This can still be overridden by the cma
>   command-line option.
>
> If this patch is not applied, KMS drivers using CMA would
> rapidly exhaust the allocated memory. This was seen on tegra_drm
> (from tagr libdrm/opentegra with exa support on freedesktop.org)
> ...
> kernel: host1x drm: failed to allocate buffer with size 2457600
> ...
>
> On the other side, CMA allocated memory can easily be freed
> http://lwn.net/Articles/486301/
> "Freeing memory is much simpler process..."
> Whereas they can only be allocated at boot time
> https://lkml.org/lkml/2014/5/7/810
> "CMA is introduced to provide physically contiguous pages at runtime.
> For this purpose, it reserves memory at boot time."
>
> This patch is about to have a convenient generic default
> and to match upstream kernel default value.
> Everything can be setup back into fedora tools such as arm-boot-config
>
> At some point, tegra revisions that can support IOMMU  will not
> rely on CMA. This is not the case for tegra20
>
> Tested on Toshiba AC100 (with 512M RAM with cma=128M zram=1x128M)
> with opentegra DDX driver
> ---
>  config-arm-generic |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/config-arm-generic b/config-arm-generic
> index 0c5242c..158ea5c 100644
> --- a/config-arm-generic
> +++ b/config-arm-generic
> @@ -162,7 +162,7 @@ CONFIG_THERMAL_GOV_USER_SPACE=y
>  CONFIG_CMA=y
>  CONFIG_DMA_CMA=y
>  # CONFIG_CMA_DEBUG is not set
> -CONFIG_CMA_SIZE_MBYTES=16
> +CONFIG_CMA_SIZE_MBYTES=64
>  CONFIG_CMA_SIZE_SEL_MBYTES=y
>  # CONFIG_CMA_SIZE_SEL_PERCENTAGE is not set
>  # CONFIG_CMA_SIZE_SEL_MIN is not set
> --
> 1.7.2.1
>
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