[PATCH v2 2/2] drm/rockchip: vop: fix irq disabled after vop driver probed

[Robin Murphy]

On 28/05/18 14:20, Heiko Stuebner wrote:
> From: Sandy Huang <hjc at rock-chips.com>
> 
> The vop irq is shared between vop and iommu and irq probing in the
> iommu driver moved to the probe function recently. This can in some
> cases lead to a stall if the irq is triggered while the vop driver
> still has it disabled, but the vop irq handler gets called.
> 
> But there is no real need to disable the irq, as the vop can simply
> also track its enabled state and ignore irqs in that case.
> For this we can simply check the power-domain state of the vop,
> similar to how the iommu driver does it.
> 
> So remove the enable/disable handling and add appropriate condition
> to the irq handler.
> 
> changes in v2:
> - move to just check the power-domain state
> - add clock handling
> 
> Signed-off-by: Sandy Huang <hjc at rock-chips.com>
> [add commit message, moved to pm_runtime_get_if_in_use]
> Signed-off-by: Heiko Stuebner <heiko at sntech.de>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 28 ++++++++++++++-------
>   1 file changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index b55156b8ba3b..615a5b44bfe9 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -573,8 +573,6 @@ static int vop_enable(struct drm_crtc *crtc)
>   
>   	spin_unlock(&vop->reg_lock);
>   
> -	enable_irq(vop->irq);
> -
>   	drm_crtc_vblank_on(crtc);
>   
>   	return 0;
> @@ -618,8 +616,6 @@ static void vop_crtc_atomic_disable(struct drm_crtc *crtc,
>   
>   	vop_dsp_hold_valid_irq_disable(vop);
>   
> -	disable_irq(vop->irq);
> -
>   	vop->is_enabled = false;
>   
>   	/*
> @@ -1195,6 +1191,16 @@ static irqreturn_t vop_isr(int irq, void *data)
>   	uint32_t active_irqs;
>   	int ret = IRQ_NONE;
>   
> +	/*
> +	 * The irq is shared with the iommu. If the power-domain is off
> +	 * the irq has to be targetted at the iommu.

Hmm, aren't the IOMMUs in the same power domain as their respective 
master, though? I would naively assume so, and it does look that way 
from the DTs in the BSP kernel.

AFAICS the IOMMU usage count should never be greater than the VOP usage 
count (except before the VOP driver has probed, but I don't think that 
matters), so although this looks like a sensible change in general I 
can't help be a little bit puzzled at how and why the flow works.

Robin.

> +	 */
> +	if (!pm_runtime_get_if_in_use(vop->dev))
> +		return IRQ_NONE;
> +
> +	if (WARN_ON(vop_core_clks_enable(vop)))
> +		goto out;
> +
>   	/*
>   	 * interrupt register has interrupt status, enable and clear bits, we
>   	 * must hold irq_lock to avoid a race with enable/disable_vblank().
> @@ -1209,8 +1215,11 @@ static irqreturn_t vop_isr(int irq, void *data)
>   	spin_unlock(&vop->irq_lock);
>   
>   	/* This is expected for vop iommu irqs, since the irq is shared */
> -	if (!active_irqs)
> -		return IRQ_NONE;
> +	if (!active_irqs) {
> +		ret = IRQ_NONE;
> +		vop_core_clks_disable(vop);
> +		goto out;
> +	}
>   
>   	if (active_irqs & DSP_HOLD_VALID_INTR) {
>   		complete(&vop->dsp_hold_completion);
> @@ -1236,6 +1245,10 @@ static irqreturn_t vop_isr(int irq, void *data)
>   		DRM_DEV_ERROR(vop->dev, "Unknown VOP IRQs: %#02x\n",
>   			      active_irqs);
>   
> +	vop_core_clks_disable(vop);
> +
> +out:
> +	pm_runtime_put(vop->dev);
>   	return ret;
>   }
>   
> @@ -1614,9 +1627,6 @@ static int vop_bind(struct device *dev, struct device *master, void *data)
>   	if (ret)
>   		goto err_disable_pm_runtime;
>   
> -	/* IRQ is initially disabled; it gets enabled in power_on */
> -	disable_irq(vop->irq);
> -
>   	return 0;
>   
>   err_disable_pm_runtime:
>