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From: Matt Coster <Matt.Coster@imgtec.com>
To: Lu Yao <yaolu@kylinos.cn>
CC: Frank Binns <Frank.Binns@imgtec.com>,
        Maarten Lankhorst
	<maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Dave Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        "dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/imagination: Kconfig: add 'PAGE_SIZE=4K' dependency
Thread-Topic: [PATCH] drm/imagination: Kconfig: add 'PAGE_SIZE=4K' dependency
Thread-Index: AQHaaeV54b+iImOcgUevYh//vZMVK7Efk0GA
Date: Wed, 28 Feb 2024 10:47:30 +0000
Message-ID: <676ec638-9ed0-4f7a-8845-1cd1804a15b2@imgtec.com>
References: <20240228012313.5934-1-yaolu@kylinos.cn>
In-Reply-To: <20240228012313.5934-1-yaolu@kylinos.cn>
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From: Matt Coster <matt.coster@imgtec.com>
To: Lu Yao <yaolu@kylinos.cn>
Cc: Frank Binns <frank.binns@imgtec.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 Dave Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Message-ID: <676ec638-9ed0-4f7a-8845-1cd1804a15b2@imgtec.com>
Subject: Re: [PATCH] drm/imagination: Kconfig: add 'PAGE_SIZE=4K' dependency
References: <20240228012313.5934-1-yaolu@kylinos.cn>
In-Reply-To: <20240228012313.5934-1-yaolu@kylinos.cn>

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Hi, thanks for the patch!

On 28/02/2024 01:23, Lu Yao wrote:
> When 'PAGE_SIZE=3D64K',the following compilation error occurs:
> "
>   ../drivers/gpu/drm/imagination/pvr_fw_mips.c: In function
> =E2=80=98pvr_mips_fw_process=E2=80=99:
>   ../drivers/gpu/drm/imagination/pvr_fw_mips.c:140:60: error: array
> subscript 0 is outside the bounds of an interior zero-length array
> =E2=80=98dma_addr_t[0]=E2=80=99 {aka =E2=80=98long long unsigned int[]=E2=
=80=99}
> [-Werror=3Dzero-length-bounds]
>   140 |   boot_data->pt_phys_addr[page_nr] =3D
> mips_data->pt_dma_addr[src_page_nr] +
> ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
>   In file included from ../drivers/gpu/drm/imagination/pvr_fw_mips.c:6:=

>   ../drivers/gpu/drm/imagination/pvr_fw_mips.h:30:13: note: while
> referencing =E2=80=98pt_dma_addr=E2=80=99
>    30 |  dma_addr_t pt_dma_addr[PVR_MIPS_PT_PAGE_COUNT];
> "
>=20
> This is because 'PVR_MIPS_PT_PAGE_COUNT' is defined as
> '(ROGUE_MIPSFW_MAX_NUM_PAGETABLE_PAGES * ROGUE_MIPSFW_PAGE_SIZE_4K) \
>>> PAGE_SHIFT', and under the above conditions, 'PAGE_SHIFT' is '16',
> 'ROGUE_MIPSFW_MAX_NUM_PAGETABLE_PAGES' is '4','ROGUE_MIPSFW_PAGE_SIZE_4=
K'
> is '4096',so 'PVR_MIPS_PT_PAGE_COUNT' is '0' causing the member
> 'pt_dma_addr' to be incorrectly defined.

The whole MIPS page table system is supposed to be host page-size
agnostic. In practice, we don=E2=80=99t regularly test on non-4K platform=
s so
this may well be broken in subtle or not-so-subtle (as in this instance)
ways. There has been at least some testing with 64K host pages =E2=80=93 =
the
configs from TI for the AM62-SK dev boards have that as the default (or
at least they did when we started working with them).

I=E2=80=99m loathed to accept this patch without at least investigating h=
ow deep
the problems go; the true fix here should be to fix the problems causing
this build error rather than just gating off non-4K hosts.

I=E2=80=99ll have a dig this afternoon to see what I can find. Did you tr=
y
anything to fix this yourself? It would be nice to not duplicate effort
on this if you have.

Cheers,
Matt

> Signed-off-by: Lu Yao <yaolu@kylinos.cn>
> ---
>  drivers/gpu/drm/imagination/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/gpu/drm/imagination/Kconfig b/drivers/gpu/drm/imag=
ination/Kconfig
> index 3bfa2ac212dc..e585922f634d 100644
> --- a/drivers/gpu/drm/imagination/Kconfig
> +++ b/drivers/gpu/drm/imagination/Kconfig
> @@ -3,7 +3,7 @@
> =20
>  config DRM_POWERVR
>  	tristate "Imagination Technologies PowerVR (Series 6 and later) & IMG=
 Graphics"
> -	depends on ARM64
> +	depends on (ARM64 && ARM64_PAGE_SHIFT=3D12)
>  	depends on DRM
>  	depends on PM
>  	select DRM_EXEC

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