linux-kernel - Re: [PATCH 2/6] drm/rockchip: vop: fix iommu page fault when resume

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Message-ID: <5c613e33-f5f2-6b5f-69a6-cc3a7aa93a71@rock-chips.com>
Date:   Thu, 3 Aug 2017 21:06:27 +0800
From:   Sandy Huang <sandy.huang@...k-chips.com>
To:     Mark Yao <mark.yao@...k-chips.com>,
        David Airlie <airlied@...ux.ie>,
        Heiko Stuebner <heiko@...ech.de>
Cc:     linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] drm/rockchip: vop: fix iommu page fault when resume

Hi mark,

在 2017/7/31 17:49, Mark Yao 写道:
> Iommu would get page fault with following path:
>     vop_disable:
>        1, disable all windows and set vop config done
>        2, vop enter to standy, all windows not works, but their registers
>           are not clean, when you read window's enable bit, may found the
>           window is enable.
> 
>     vop_enable:
>        1, memcpy(vop->regsbak, vop->regs, len)
>           save current vop registers to vop->regsbak, then you can found
>           window is enable on regsbak.
>        2, VOP_WIN_SET(vop, win, gate, 1);
>           force enable window gate, but gate and enable are on same
>           hardware register, then window enable bit rewrite to vop hardware.
>        3, vop power on, and vop might try to scan destroyed buffer,
>           then iommu get page fault.
> 
> Move windows disable after vop regsbak restore, then vop regsbak mechanism
> would keep tracing the modify, everything would be safe.
> 
> Signed-off-by: Mark Yao <mark.yao@...k-chips.com>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 33 +++++++++++++----------------
>   1 file changed, 15 insertions(+), 18 deletions(-)
> 

Reviewed-by: Sandy huang <sandy.huang@...k-chips.com>