[PATCH] ARM: exynos_defconfig - enable CONFIG_EXYNOS_IOMMU

[PATCH] ARM: exynos_defconfig - enable CONFIG_EXYNOS_IOMMU

[Shuah Khan]

EXYNOS_IOMMU is disabled in exynos_defconfig since it is known to cause
boot failures on Exynos Chrome-books. The recommendation is for IOMMU to
be enabled manually on systems as needed.

A recent exynos_drm change added a warning message when EXYNOS_IOMMU is
disabled. It is necessary to enable it to avoid the warning messages.
A few initial tests have shown that enabling EXYNOS_IOMMU might be safe
on Exynos Chrome-books.

Enable CONFIG_EXYNOS_IOMMU in exynos_defconfig.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
---
 arch/arm/configs/exynos_defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
index f1d7834..0ccd5eb 100644
--- a/arch/arm/configs/exynos_defconfig
+++ b/arch/arm/configs/exynos_defconfig
@@ -281,6 +281,7 @@ CONFIG_DEVFREQ_GOV_POWERSAVE=y
 CONFIG_DEVFREQ_GOV_USERSPACE=y
 CONFIG_ARM_EXYNOS_BUS_DEVFREQ=y
 CONFIG_DEVFREQ_EVENT_EXYNOS_NOCP=y
+CONFIG_EXYNOS_IOMMU=y
 CONFIG_EXTCON=y
 CONFIG_EXTCON_MAX14577=y
 CONFIG_EXTCON_MAX77693=y
-- 
2.7.4

[PATCH] ARM: exynos_defconfig - enable CONFIG_EXYNOS_IOMMU

[Marek Szyprowski]

Hi Shuah,

On 2017-12-12 22:31, Shuah Khan wrote:
> EXYNOS_IOMMU is disabled in exynos_defconfig since it is known to cause
> boot failures on Exynos Chrome-books. The recommendation is for IOMMU to
> be enabled manually on systems as needed.
>
> A recent exynos_drm change added a warning message when EXYNOS_IOMMU is
> disabled. It is necessary to enable it to avoid the warning messages.
> A few initial tests have shown that enabling EXYNOS_IOMMU might be safe
> on Exynos Chrome-books.
>
> Enable CONFIG_EXYNOS_IOMMU in exynos_defconfig.
>
> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

Due to some other changes in the order of operations during boot process,
power domains are initialized very early and because of the temporary
lack of devices (which are not yet added to the system), are turned off.

This practically stops FIMD for scanning framebuffer very early during
boot, before IOMMU gets initialized and "solves" the issue, which was
the reason to disable Exynos IOMMU by default.

Like I've already said, I've checked Exynos Snow Chromebook boots fine
with IOMMU support enabled, both with v4.15-rc3 and linux-next.

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
>   arch/arm/configs/exynos_defconfig | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
> index f1d7834..0ccd5eb 100644
> --- a/arch/arm/configs/exynos_defconfig
> +++ b/arch/arm/configs/exynos_defconfig
> @@ -281,6 +281,7 @@ CONFIG_DEVFREQ_GOV_POWERSAVE=y
>   CONFIG_DEVFREQ_GOV_USERSPACE=y
>   CONFIG_ARM_EXYNOS_BUS_DEVFREQ=y
>   CONFIG_DEVFREQ_EVENT_EXYNOS_NOCP=y
> +CONFIG_EXYNOS_IOMMU=y
>   CONFIG_EXTCON=y
>   CONFIG_EXTCON_MAX14577=y
>   CONFIG_EXTCON_MAX77693=y

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

[PATCH] ARM: exynos_defconfig - enable CONFIG_EXYNOS_IOMMU

[Krzysztof Kozlowski]

On Wed, Dec 13, 2017 at 10:42:33AM +0100, Marek Szyprowski wrote:
> Hi Shuah,
> 
> On 2017-12-12 22:31, Shuah Khan wrote:
> > EXYNOS_IOMMU is disabled in exynos_defconfig since it is known to cause
> > boot failures on Exynos Chrome-books. The recommendation is for IOMMU to
> > be enabled manually on systems as needed.
> > 
> > A recent exynos_drm change added a warning message when EXYNOS_IOMMU is
> > disabled. It is necessary to enable it to avoid the warning messages.
> > A few initial tests have shown that enabling EXYNOS_IOMMU might be safe
> > on Exynos Chrome-books.
> > 
> > Enable CONFIG_EXYNOS_IOMMU in exynos_defconfig.
> > 
> > Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
> 
> Due to some other changes in the order of operations during boot process,
> power domains are initialized very early and because of the temporary
> lack of devices (which are not yet added to the system), are turned off.
> 
> This practically stops FIMD for scanning framebuffer very early during
> boot, before IOMMU gets initialized and "solves" the issue, which was
> the reason to disable Exynos IOMMU by default.
> 
> Like I've already said, I've checked Exynos Snow Chromebook boots fine
> with IOMMU support enabled, both with v4.15-rc3 and linux-next.
> 
> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Thanks, applied with rephrased and extended message using Marek's
explanation.

Best regards,
Krzysztof