| Message ID | 20221101152629.21768-1-marex@denx.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm: lcdif: Set and enable FIFO Panic threshold | expand |
On Tue, 2022-11-01 at 16:26 +0100, Marek Vasut wrote: > In case the LCDIFv3 is used to drive a 4k panel via i.MX8MP HDMI > bridge, > the LCDIFv3 becomes susceptible to FIFO underflows, these lead to > nasty > flicker of the image on the panel, or image being shifted by half > frame > horizontally every second frame. The flicker can be easily triggered > by > running 3D application on top of weston compositor, like neverball or > chromium. Surprisingly glmark2-es2-wayland or glmark2-es2-drm does > not > trigger this effect so easily. > > Configure the FIFO Panic threshold register and enable the FIFO Panic > mode, which internally boosts the NoC interconnect priority for > LCDIFv3 > transactions in case of possible underflow. This mitigates the > flicker > effect on 4k panels as well. > > Fixes: 9db35bb349a0 ("drm: lcdif: Add support for i.MX8MP LCDIF > variant") > Signed-off-by: Marek Vasut <marex@denx.de> > --- > Cc: Kieran Bingham <kieran.bingham@ideasonboard.com> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Cc: Liu Ying <victor.liu@nxp.com> > Cc: Lucas Stach <l.stach@pengutronix.de> > Cc: Marco Felsch <m.felsch@pengutronix.de> > Cc: Martyn Welch <martyn.welch@collabora.com> > Cc: Peng Fan <peng.fan@nxp.com> > Cc: Sam Ravnborg <sam@ravnborg.org> > --- > V2: - Include bitfield.h to always obtain FIELD_PREP definition > - Rename PANIC0_THRES_RANGE to PANIC0_THRES_MAX and set to 511 > - Move threshold configuration and enable before FIFO and > scanout enable and vice versa for disable > --- > drivers/gpu/drm/mxsfb/lcdif_kms.c | 16 ++++++++++++++++ > drivers/gpu/drm/mxsfb/lcdif_regs.h | 1 + > 2 files changed, 17 insertions(+) > > diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c > b/drivers/gpu/drm/mxsfb/lcdif_kms.c > index a5302006c02cd..09280c6c3bbc1 100644 > --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c > +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c > @@ -5,6 +5,7 @@ > * This code is based on drivers/gpu/drm/mxsfb/mxsfb* > */ > > +#include <linux/bitfield.h> > #include <linux/clk.h> > #include <linux/io.h> > #include <linux/iopoll.h> > @@ -334,6 +335,18 @@ static void lcdif_enable_controller(struct > lcdif_drm_private *lcdif) > { > u32 reg; > > + /* Set FIFO Panic watermarks, low 1/3, high 2/3 . */ > + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_MAX / > 3) | > + FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_MAX > / 3), Like I mentioned in v1 review cycle, I still think it's better to define PANIC0_THRES_{LOW,HIGH}(n) macros in lcdif_regs.h instead of using FIELD_PREP here directly. Otherwise, Tested-by: Liu Ying <victor.liu@nxp.com> # i.MX8mp EVK "koe,tx26d202vm0bwa" LVDS panel fb console Reviewed-by: Liu Ying <victor.liu@nxp.com> [...] Regards, Liu Ying
diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c b/drivers/gpu/drm/mxsfb/lcdif_kms.c index a5302006c02cd..09280c6c3bbc1 100644 --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c @@ -5,6 +5,7 @@ * This code is based on drivers/gpu/drm/mxsfb/mxsfb* */ +#include <linux/bitfield.h> #include <linux/clk.h> #include <linux/io.h> #include <linux/iopoll.h> @@ -334,6 +335,18 @@ static void lcdif_enable_controller(struct lcdif_drm_private *lcdif) { u32 reg; + /* Set FIFO Panic watermarks, low 1/3, high 2/3 . */ + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_MAX / 3) | + FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_MAX / 3), + lcdif->base + LCDC_V8_PANIC0_THRES); + + /* + * Enable FIFO Panic, this does not generate interrupt, but + * boosts NoC priority based on FIFO Panic watermarks. + */ + writel(INT_ENABLE_D1_PLANE_PANIC_EN, + lcdif->base + LCDC_V8_INT_ENABLE_D1); + reg = readl(lcdif->base + LCDC_V8_DISP_PARA); reg |= DISP_PARA_DISP_ON; writel(reg, lcdif->base + LCDC_V8_DISP_PARA); @@ -361,6 +374,9 @@ static void lcdif_disable_controller(struct lcdif_drm_private *lcdif) reg = readl(lcdif->base + LCDC_V8_DISP_PARA); reg &= ~DISP_PARA_DISP_ON; writel(reg, lcdif->base + LCDC_V8_DISP_PARA); + + /* Disable FIFO Panic NoC priority booster. */ + writel(0, lcdif->base + LCDC_V8_INT_ENABLE_D1); } static void lcdif_reset_block(struct lcdif_drm_private *lcdif) diff --git a/drivers/gpu/drm/mxsfb/lcdif_regs.h b/drivers/gpu/drm/mxsfb/lcdif_regs.h index fb74eb5ccbf1d..c55dfb236c1d3 100644 --- a/drivers/gpu/drm/mxsfb/lcdif_regs.h +++ b/drivers/gpu/drm/mxsfb/lcdif_regs.h @@ -255,6 +255,7 @@ #define PANIC0_THRES_LOW_MASK GENMASK(24, 16) #define PANIC0_THRES_HIGH_MASK GENMASK(8, 0) +#define PANIC0_THRES_MAX 511 #define LCDIF_MIN_XRES 120 #define LCDIF_MIN_YRES 120
In case the LCDIFv3 is used to drive a 4k panel via i.MX8MP HDMI bridge, the LCDIFv3 becomes susceptible to FIFO underflows, these lead to nasty flicker of the image on the panel, or image being shifted by half frame horizontally every second frame. The flicker can be easily triggered by running 3D application on top of weston compositor, like neverball or chromium. Surprisingly glmark2-es2-wayland or glmark2-es2-drm does not trigger this effect so easily. Configure the FIFO Panic threshold register and enable the FIFO Panic mode, which internally boosts the NoC interconnect priority for LCDIFv3 transactions in case of possible underflow. This mitigates the flicker effect on 4k panels as well. Fixes: 9db35bb349a0 ("drm: lcdif: Add support for i.MX8MP LCDIF variant") Signed-off-by: Marek Vasut <marex@denx.de> --- Cc: Kieran Bingham <kieran.bingham@ideasonboard.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Liu Ying <victor.liu@nxp.com> Cc: Lucas Stach <l.stach@pengutronix.de> Cc: Marco Felsch <m.felsch@pengutronix.de> Cc: Martyn Welch <martyn.welch@collabora.com> Cc: Peng Fan <peng.fan@nxp.com> Cc: Sam Ravnborg <sam@ravnborg.org> --- V2: - Include bitfield.h to always obtain FIELD_PREP definition - Rename PANIC0_THRES_RANGE to PANIC0_THRES_MAX and set to 511 - Move threshold configuration and enable before FIFO and scanout enable and vice versa for disable --- drivers/gpu/drm/mxsfb/lcdif_kms.c | 16 ++++++++++++++++ drivers/gpu/drm/mxsfb/lcdif_regs.h | 1 + 2 files changed, 17 insertions(+)