Re: [PATCH] drm/rockchip: vop: Reset yrgb_mst when re-enabling

Mark yao
2016-03-19T01:16:10Z

On 2016年03月18日 19:22, Tomeu Vizoso wrote:
> When the VOP is re-enabled, it will start scanning right away the
> framebuffers that were configured from the last time, even if those have
> been destroyed already. To prevent the VOP from trying to access freed
> memory, reset the registers that hold pointers to framebuffers right
> after we can write to them, but before the VOP is awaken from standby.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> Link: http://lkml.kernel.org/g/CAAObsKAv+05ih5U+=4kic_NsjGMhfxYheHR8xXXmacZs+p5SHw@mail.gmail.com
> ---
> drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 5e57f5b2e4b0..0df91c28740b 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -429,6 +429,7 @@ static void vop_dsp_hold_valid_irq_disable(struct vop *vop)
> static void vop_enable(struct drm_crtc *crtc)
> {
> struct vop *vop = to_vop(crtc);
> + int i;
> int ret;
>
> if (vop->is_enabled)
> @@ -476,6 +477,18 @@ static void vop_enable(struct drm_crtc *crtc)
> */
> vop->is_enabled = true;
>
> + /*
> + * Before turning the VOP completely on, unset the registers
> + * containing FB addresses to avoid the HW start scanning old FBs.
> + */
> + for (i = 0; i < vop->data->win_size; i++) {
> + struct vop_win *vop_win = &vop->win[i];
> + const struct vop_win_data *win = vop_win->data;
> +
> + VOP_WIN_SET(vop, win, yrgb_mst, 0x0);
> + VOP_WIN_SET(vop, win, uv_mst, 0x0);
> + }
> +
Hi Tomeu

Thanks for your fix.

Set yrgb_mst and uv_mst is not a good idea, because 0x0 also is a memory
buffer address, ddr will access the 0x0 buffer.
I think you may enable DRM_FBDEV_EMULATION, the 0x0 address is iommu
mmaped address for fbdev, so your test can works.
but if DRM_FBDEV_EMULATION is not define, may be 0x0 address is
unmmaped, would get the iommu crash.

I think we can use atomic disable function like this:
for_each_plane_in_state(old_state, plane, old_plane_state, i) {
const struct drm_plane_helper_funcs *funcs;
funcs = plane->helper_private;
funcs->atomic_disable(plane, old_plane_state);
}

But I think we'd better find why we need do this hack here.

Does the old FB address is ummaped when crtc disabling? why plane is not
disabled?

Thanks.

> spin_lock(&vop->reg_lock);
>
> VOP_CTRL_SET(vop, standby, 0);

--
Ｍark Yao