Re: [PATCH 01/25] drm: kirin: Fix for hikey620 display offset problem

Sam Ravnborg
2019-04-24T16:36:07Z

Hi John.

On Tue, Apr 23, 2019 at 04:20:32PM -0700, John Stultz wrote:
> From: Da Lv <lvda3@hisilicon.com>
>
> The original HiKey (620) board has had a long running issue
> where when using a 1080p montior, the display would occasionally
> blink and come come back with a horizontal offset (usually also
> shifting the colors, depending on the value of the offset%4).
>
> After lots of analysis by HiSi developers, they found the issue
> was due to when running at 1080p, it was possible to hit the
> device memory bandwidth limits, which could cause the DSI signal
> to get out of sync.
>
> Unfortunately the DSI logic doesn't have the ability to
> automatically recover from this situation, but we can get a an
> LDI underflow interrupt when it happens.
>
> To then correct the issue, when we get an LDI underflow irq, we
> we can simply suspend and resume the display, which resets the
> hardware.
>
> Thus, this patch enables the ldi underflow interrupt, and
> initializes a workqueue that is used to suspend/resume the
> display to recover. Then when the irq occurs we clear it and
> schedule the workqueue to reset display engine.
>
> Cc: Xinliang Liu <z.liuxinliang@hisilicon.com>
> Cc: Rongrong Zou <zourongrong@gmail.com>
> Cc: Xinwei Kong <kong.kongxinwei@hisilicon.com>
> Cc: Chen Feng <puck.chen@hisilicon.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: dri-devel <dri-devel@lists.freedesktop.org>
> Signed-off-by: Da Lv <lvda3@hisilicon.com>
> Signed-off-by: Yidong Lin <linyidong@huawei.com>
> [jstultz: Reworded the commit message, checkpatch cleanups]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Minor cleanups
> ---
> drivers/gpu/drm/hisilicon/kirin/kirin_ade_reg.h | 6 ++++++
> drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c | 22 ++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_ade_reg.h b/drivers/gpu/drm/hisilicon/kirin/kirin_ade_reg.h
> index 4cf281b7..ced40c6 100644
> --- a/drivers/gpu/drm/hisilicon/kirin/kirin_ade_reg.h
> +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_ade_reg.h
> @@ -87,6 +87,7 @@
> #define VSIZE_OFST 20
> #define LDI_INT_EN 0x741C
> #define FRAME_END_INT_EN_OFST 1
> +#define UNDERFLOW_INT_EN_OFST 2
> #define LDI_CTRL 0x7420
> #define BPP_OFST 3
> #define DATA_GATE_EN BIT(2)
> @@ -97,6 +98,11 @@
> #define LDI_HDMI_DSI_GT 0x7434
>
> /*
> + *BIT_LDI_UNFLOW
> + */
> +#define BIT_LDI_UNFLOW BIT(2)

The definition of this bit looks not like anything surrounding it.
And it is not obvious that this bit is part of LDI_MSK_INT.
Consider to reformat this so it is obvious where this bit belongs
when reading the .h file.

> +
> +/*
> * ADE media bus service regs
> */
> #define ADE0_QOSGENERATOR_MODE 0x010C
> diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> index 73611a9..beb2a3c 100644
> --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
> @@ -58,6 +58,7 @@ struct ade_hw_ctx {
> struct ade_crtc {
> struct drm_crtc base;
> struct ade_hw_ctx *ctx;
> + struct work_struct drm_device_wq;
> bool enable;
> u32 out_format;
> };
> @@ -176,6 +177,7 @@ static void ade_init(struct ade_hw_ctx *ctx)
> */
> ade_update_bits(base + ADE_CTRL, FRM_END_START_OFST,
> FRM_END_START_MASK, REG_EFFECTIVE_IN_ADEEN_FRMEND);
> + ade_update_bits(base + LDI_INT_EN, UNDERFLOW_INT_EN_OFST, MASK(1), 1);
> }
>
> static bool ade_crtc_mode_fixup(struct drm_crtc *crtc,
> @@ -345,6 +347,17 @@ static void ade_crtc_disable_vblank(struct drm_crtc *crtc)
> MASK(1), 0);
> }
>
> +static void drm_underflow_wq(struct work_struct *work)
> +{
> + struct ade_crtc *acrtc = container_of(work, struct ade_crtc,
> + drm_device_wq);
> + struct drm_device *drm_dev = (&acrtc->base)->dev;
> + struct drm_atomic_state *state;
> +
> + state = drm_atomic_helper_suspend(drm_dev);
> + drm_atomic_helper_resume(drm_dev, state);
> +}
> +
> static irqreturn_t ade_irq_handler(int irq, void *data)
> {
> struct ade_crtc *acrtc = data;
> @@ -362,6 +375,12 @@ static irqreturn_t ade_irq_handler(int irq, void *data)
> MASK(1), 1);
> drm_crtc_handle_vblank(crtc);
> }
> + if (status & BIT_LDI_UNFLOW) {
> + ade_update_bits(base + LDI_INT_CLR, UNDERFLOW_INT_EN_OFST,
> + MASK(1), 1);
A general comment here.
It is not obvious from reading this code that the code will clear
LDI_UNFLOW bit in the LDI_INT_CLR register.

I think this driver could see readability improvements
if converted to use regmaps.

Sam