Re: [PATCH v3 1/4] drm/mxsfb: Fix initial corrupt frame when activating display
From: Stefan Agner
Date: Tue Aug 07 2018 - 14:29:53 EST
On 06.08.2018 21:31, Leonard Crestez wrote:
> LCDIF will repeatedly display data from CUR_BUF and set CUR_BUF to
> NEXT_BUF when done. Since we are only ever writing to NEXT_BUF the
> display will show an initial corrupt frame.
>
> Fix by writing the FB paddr to both CUR_BUF and NEXT_BUF when
> activating the CRTC.
Really like how this patch set evolves! Only some minor thing below...
>
> Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
> ---
> drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 42 +++++++++++++++++++++---------
> 1 file changed, 29 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> index 0abe77675b76..db3ff5bde122 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> @@ -194,15 +194,31 @@ static int mxsfb_reset_block(void __iomem *reset_addr)
> return ret;
>
> return clear_poll_bit(reset_addr, MODULE_CLKGATE);
> }
>
> +static dma_addr_t mxsfb_get_fb_paddr(struct mxsfb_drm_private *mxsfb)
> +{
> + struct drm_framebuffer *fb = mxsfb->pipe.plane.state->fb;
> + struct drm_gem_cma_object *gem;
> +
> + if (!fb)
> + return 0;
> +
> + gem = drm_fb_cma_get_gem_obj(fb, 0);
> + if (!gem)
> + return 0;
> +
> + return gem->paddr;
> +}
> +
> static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
> {
> struct drm_display_mode *m = &mxsfb->pipe.crtc.state->adjusted_mode;
> const u32 bus_flags = mxsfb->connector.display_info.bus_flags;
> u32 vdctrl0, vsync_pulse_len, hsync_pulse_len;
> + dma_addr_t paddr;
> int err;
>
> /*
> * It seems, you can't re-program the controller if it is still
> * running. This may lead to shifted pictures (FIFO issue?), so
> @@ -268,10 +284,16 @@ static void mxsfb_crtc_mode_set_nofb(struct
> mxsfb_drm_private *mxsfb)
> mxsfb->base + LCDC_VDCTRL3);
>
> writel(SET_DOTCLK_H_VALID_DATA_CNT(m->hdisplay),
> mxsfb->base + LCDC_VDCTRL4);
>
> + /* Update cur_buf as well to avoid an initial corrupt frame */
> + paddr = mxsfb_get_fb_paddr(mxsfb);
> + if (paddr) {
> + writel(paddr, mxsfb->base + mxsfb->devdata->cur_buf);
> + writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> + }
Traditionally mxsfb_crtc_mode_set_nofb() was used as a callback to
mode_set_nofb. And that callback should not fiddle with the fb (as the
name says).
So I rather prefer to move the new bits to mxsfb_crtc_enable(), between
mxsfb_crtc_mode_set_nofb() and mxsfb_enable_controller(). It is only
cosmetics, but I'd rather prefer to have it in the right place.
Currently the AXI clock is disabled between those functions... I suggest
to enable the AXI clock once in mxsfb_crtc_enable(). This puts an end to
the unnecessary enable/disable/enable sequence in mxsfb_crtc_enable().
So I suggest to create a patch "drm/mxsfb: simplify AXI clock handling"
--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -129,7 +129,6 @@ static void mxsfb_enable_controller(struct
mxsfb_drm_private *mxsfb)
if (mxsfb->clk_disp_axi)
clk_prepare_enable(mxsfb->clk_disp_axi);
clk_prepare_enable(mxsfb->clk);
- mxsfb_enable_axi_clk(mxsfb);
/* If it was disabled, re-enable the mode again */
writel(CTRL_DOTCLK_MODE, mxsfb->base + LCDC_CTRL + REG_SET);
@@ -159,8 +158,6 @@ static void mxsfb_disable_controller(struct
mxsfb_drm_private *mxsfb)
reg &= ~VDCTRL4_SYNC_SIGNALS_ON;
writel(reg, mxsfb->base + LCDC_VDCTRL4);
- mxsfb_disable_axi_clk(mxsfb);
-
clk_disable_unprepare(mxsfb->clk);
if (mxsfb->clk_disp_axi)
clk_disable_unprepare(mxsfb->clk_disp_axi);
@@ -208,7 +205,6 @@ static void mxsfb_crtc_mode_set_nofb(struct
mxsfb_drm_private *mxsfb)
* running. This may lead to shifted pictures (FIFO issue?), so
* first stop the controller and drain its FIFOs.
*/
- mxsfb_enable_axi_clk(mxsfb);
/* Mandatory eLCDIF reset as per the Reference Manual */
err = mxsfb_reset_block(mxsfb->base);
@@ -269,12 +265,11 @@ static void mxsfb_crtc_mode_set_nofb(struct
mxsfb_drm_private *mxsfb)
writel(SET_DOTCLK_H_VALID_DATA_CNT(m->hdisplay),
mxsfb->base + LCDC_VDCTRL4);
-
- mxsfb_disable_axi_clk(mxsfb);
}
void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb)
{
+ mxsfb_enable_axi_clk(mxsfb);
mxsfb_crtc_mode_set_nofb(mxsfb);
mxsfb_enable_controller(mxsfb);
}
@@ -282,6 +277,7 @@ void mxsfb_crtc_enable(struct mxsfb_drm_private
*mxsfb)
void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
{
mxsfb_disable_controller(mxsfb);
+ mxsfb_disable_axi_clk(mxsfb);
}
Then move the above section between mxsfb_crtc_mode_set_nofb() and
mxsfb_enable_controller().
--
Stefan
> mxsfb_disable_axi_clk(mxsfb);
> }
>
> void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb)
> {
> @@ -287,16 +309,12 @@ void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
> void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
> struct drm_plane_state *state)
> {
> struct drm_simple_display_pipe *pipe = &mxsfb->pipe;
> struct drm_crtc *crtc = &pipe->crtc;
> - struct drm_framebuffer *fb = pipe->plane.state->fb;
> struct drm_pending_vblank_event *event;
> - struct drm_gem_cma_object *gem;
> -
> - if (!crtc)
> - return;
> + dma_addr_t paddr;
>
> spin_lock_irq(&crtc->dev->event_lock);
> event = crtc->state->event;
> if (event) {
> crtc->state->event = NULL;
> @@ -307,14 +325,12 @@ void mxsfb_plane_atomic_update(struct
> mxsfb_drm_private *mxsfb,
> drm_crtc_send_vblank_event(crtc, event);
> }
> }
> spin_unlock_irq(&crtc->dev->event_lock);
>
> - if (!fb)
> - return;
> -
> - gem = drm_fb_cma_get_gem_obj(fb, 0);
> -
> - mxsfb_enable_axi_clk(mxsfb);
> - writel(gem->paddr, mxsfb->base + mxsfb->devdata->next_buf);
> - mxsfb_disable_axi_clk(mxsfb);
> + paddr = mxsfb_get_fb_paddr(mxsfb);
> + if (paddr) {
> + mxsfb_enable_axi_clk(mxsfb);
> + writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> + mxsfb_disable_axi_clk(mxsfb);
> + }
> }