Re: [PATCH v3 1/4] drm/rockchip: vop: export line flag function

[Sean Paul]

On Fri, Jul 1, 2016 at 5:19 AM, Yakir Yang <ykk@xxxxxxxxxxxxxx> wrote:
> VOP have integrated a hardware counter which indicate the exact display
> line that vop is scanning. And if we're interested in a specific line,
> we can set the line number to vop line_flag register, and then vop would
> generate a line_flag interrupt for it.
>
> For example eDP PSR function is interested in the vertical blanking
> period, then driver could set the line number to zero.
>
> This patch have exported a symbol that allow other driver to listen the
> line flag event with given timeout limit:
> -  rockchip_drm_wait_line_flag()
>
> Signed-off-by: Yakir Yang <ykk@xxxxxxxxxxxxxx>
> ---
> Changes in v3:
> - Export the 'rockchip_drm_wait_line_flag' symbol, and document it.
> - Add 'line_flag_num_0' for RK3288/RK3036
> - Remove the notify for waiting line_flag event (Daniel)
>
> Changes in v2:
> - Introduce in v2, split VOP line flag changes out
>
>  drivers/gpu/drm/rockchip/rockchip_drm_drv.h |   3 +
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 103 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.h |   3 +
>  drivers/gpu/drm/rockchip/rockchip_vop_reg.c |   4 ++
>  4 files changed, 113 insertions(+)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> index ea39329..239b830 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> @@ -70,4 +70,7 @@ int rockchip_drm_dma_attach_device(struct drm_device *drm_dev,
>                                    struct device *dev);
>  void rockchip_drm_dma_detach_device(struct drm_device *drm_dev,
>                                     struct device *dev);
> +int rockchip_drm_wait_line_flag(struct drm_crtc *crtc, unsigned int line_num,
> +                               unsigned int mstimeout);
> +
>  #endif /* _ROCKCHIP_DRM_DRV_H_ */
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index c8a62a8..cd3cac5 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -121,6 +121,8 @@ struct vop {
>         /* protected by dev->event_lock */
>         struct drm_pending_vblank_event *event;
>
> +       struct completion line_flag_completion;
> +
>         const struct vop_data *data;
>
>         uint32_t *regsbak;
> @@ -431,6 +433,59 @@ static void vop_dsp_hold_valid_irq_disable(struct vop *vop)
>         spin_unlock_irqrestore(&vop->irq_lock, flags);
>  }
>
> +/*
> + * (1) each frame starts at the start of the Vsync pulse which is signaled by
> + *     the "FRAME_SYNC" interrupt.
> + * (2) the active data region of each frame ends at dsp_vact_end
> + * (3) we should program this same number (dsp_vact_end) into dsp_line_frag_num,
> + *      to get "LINE_FLAG" interrupt at the end of the active on screen data.
> + *
> + * VOP_INTR_CTRL0.dsp_line_frag_num = VOP_DSP_VACT_ST_END.dsp_vact_end
> + * Interrupts
> + * LINE_FLAG -------------------------------+
> + * FRAME_SYNC ----+                         |
> + *                |                         |
> + *                v                         v
> + *                | Vsync | Vbp |  Vactive  | Vfp |
> + *                        ^     ^           ^     ^
> + *                        |     |           |     |
> + *                        |     |           |     |
> + * dsp_vs_end ------------+     |           |     |   VOP_DSP_VTOTAL_VS_END
> + * dsp_vact_start --------------+           |     |   VOP_DSP_VACT_ST_END
> + * dsp_vact_end ----------------------------+     |   VOP_DSP_VACT_ST_END
> + * dsp_total -------------------------------------+   VOP_DSP_VTOTAL_VS_END
> + */
> +
> +static void vop_line_flag_irq_enable(struct vop *vop, int line_num)
> +{
> +       unsigned long flags;
> +
> +       if (WARN_ON(!vop->is_enabled))
> +               return;
> +
> +       spin_lock_irqsave(&vop->irq_lock, flags);
> +
> +       VOP_CTRL_SET(vop, line_flag_num_0, line_num);
> +       VOP_INTR_SET_TYPE(vop, enable, LINE_FLAG_INTR, 1);
> +       vop_cfg_done(vop);
> +
> +       spin_unlock_irqrestore(&vop->irq_lock, flags);
> +}
> +
> +static void vop_line_flag_irq_disable(struct vop *vop)
> +{
> +       unsigned long flags;
> +
> +       if (WARN_ON(!vop->is_enabled))
> +               return;
> +
> +       spin_lock_irqsave(&vop->irq_lock, flags);
> +
> +       VOP_INTR_SET_TYPE(vop, enable, LINE_FLAG_INTR, 0);
> +
> +       spin_unlock_irqrestore(&vop->irq_lock, flags);
> +}
> +
>  static void vop_enable(struct drm_crtc *crtc)
>  {
>         struct vop *vop = to_vop(crtc);
> @@ -1157,6 +1212,13 @@ static irqreturn_t vop_isr(int irq, void *data)
>                 ret = IRQ_HANDLED;
>         }
>
> +       if (active_irqs & LINE_FLAG_INTR) {
> +               if (!completion_done(&vop->line_flag_completion))
> +                       complete(&vop->line_flag_completion);

I think there's potential to miss flags here if the timing is just
right because the completion_done and complete are not atomic wrt the
wait_line_flag function. I think you need some locking around the
completion operations to ensure they're properly sequenced.

FWIW, if you're reinitializing the completion every time in
drm_wait_line_flag, you should be able to just call complete (or
complete_all) without checking if there are any waiters.


> +               active_irqs &= ~LINE_FLAG_INTR;
> +               ret = IRQ_HANDLED;
> +       }
> +
>         if (active_irqs & FS_INTR) {
>                 drm_crtc_handle_vblank(crtc);
>                 vop_handle_vblank(vop);
> @@ -1255,6 +1317,7 @@ static int vop_create_crtc(struct vop *vop)
>
>         init_completion(&vop->dsp_hold_completion);
>         init_completion(&vop->wait_update_complete);
> +       init_completion(&vop->line_flag_completion);
>         crtc->port = port;
>         rockchip_register_crtc_funcs(crtc, &private_crtc_funcs);
>
> @@ -1411,6 +1474,46 @@ static void vop_win_init(struct vop *vop)
>         }
>  }
>
> +/**
> + * rockchip_drm_wait_line_flag - acqiure the give line flag event
> + * @crtc: CRTC to enable line flag
> + * @line_num: interested line number
> + * @mstimeout: millisecond for timeout
> + *
> + * Driver would hold here until the interested line flag interrupt have
> + * happened or timeout to wait.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int rockchip_drm_wait_line_flag(struct drm_crtc *crtc, unsigned int line_num,
> +                               unsigned int mstimeout)
> +{
> +       struct vop *vop = to_vop(crtc);
> +       unsigned long jiffies_left;
> +
> +       if (!crtc || !vop->is_enabled)
> +               return -ENODEV;
> +
> +       if (line_num > crtc->mode.vtotal || mstimeout <= 0)
> +               return -EINVAL;
> +
> +       reinit_completion(&vop->line_flag_completion);
> +       vop_line_flag_irq_enable(vop, line_num);
> +

This will only work for one waiter per vop. Is it worth enforcing this
explicitly to avoid weird behavior when there are more than one?

> +       jiffies_left = wait_for_completion_timeout(&vop->line_flag_completion,
> +                                                  msecs_to_jiffies(mstimeout));
> +       vop_line_flag_irq_disable(vop);
> +
> +       if (jiffies_left == 0) {
> +               dev_err(vop->dev, "Timeout waiting for IRQ\n");
> +               return -ETIMEDOUT;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL(rockchip_drm_wait_line_flag);
> +
>  static int vop_bind(struct device *dev, struct device *master, void *data)
>  {
>         struct platform_device *pdev = to_platform_device(dev);
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> index ff4f52e..34fcd03 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> @@ -61,6 +61,9 @@ struct vop_ctrl {
>         struct vop_reg hpost_st_end;
>         struct vop_reg vpost_st_end;
>
> +       struct vop_reg line_flag_num_0;
> +       struct vop_reg line_flag_num_1;
> +

nit: you could make this an array:

struct vop_reg line_flag_num[2];


>         struct vop_reg cfg_done;
>  };
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> index 6f42e56..e9211c9 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> @@ -122,6 +122,7 @@ static const struct vop_ctrl rk3036_ctrl_data = {
>         .hact_st_end = VOP_REG(RK3036_DSP_HACT_ST_END, 0x1fff1fff, 0),
>         .vtotal_pw = VOP_REG(RK3036_DSP_VTOTAL_VS_END, 0x1fff1fff, 0),
>         .vact_st_end = VOP_REG(RK3036_DSP_VACT_ST_END, 0x1fff1fff, 0),
> +       .line_flag_num_0 = VOP_REG(RK3036_INT_STATUS, 0xfff, 12),
>         .cfg_done = VOP_REG(RK3036_REG_CFG_DONE, 0x1, 0),
>  };
>
> @@ -221,6 +222,7 @@ static const struct vop_ctrl rk3288_ctrl_data = {
>         .vact_st_end = VOP_REG(RK3288_DSP_VACT_ST_END, 0x1fff1fff, 0),
>         .hpost_st_end = VOP_REG(RK3288_POST_DSP_HACT_INFO, 0x1fff1fff, 0),
>         .vpost_st_end = VOP_REG(RK3288_POST_DSP_VACT_INFO, 0x1fff1fff, 0),
> +       .line_flag_num_0 = VOP_REG(RK3288_INTR_CTRL0, 0x1fff, 12),
>         .cfg_done = VOP_REG(RK3288_REG_CFG_DONE, 0x1, 0),
>  };
>
> @@ -299,6 +301,8 @@ static const struct vop_ctrl rk3399_ctrl_data = {
>         .vact_st_end = VOP_REG(RK3399_DSP_VACT_ST_END, 0x1fff1fff, 0),
>         .hpost_st_end = VOP_REG(RK3399_POST_DSP_HACT_INFO, 0x1fff1fff, 0),
>         .vpost_st_end = VOP_REG(RK3399_POST_DSP_VACT_INFO, 0x1fff1fff, 0),
> +       .line_flag_num_0 = VOP_REG(RK3399_LINE_FLAG, 0xffff, 0),
> +       .line_flag_num_1 = VOP_REG(RK3399_LINE_FLAG, 0xffff, 16),
>         .cfg_done = VOP_REG_MASK(RK3399_REG_CFG_DONE, 0x1, 0),
>  };
>
> --
> 1.9.1
>
>