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

From: Mark yao
Date: Fri Mar 18 2016 - 21:17:41 EST

On 2016å03æ18æ 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@xxxxxxxxxxxxx>
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?


VOP_CTRL_SET(vop, standby, 0);

ïark Yao