Re: [PATCH 2/2] nouveau: Acknowledge HPD irq in handler, not bottom half

[Ben Skeggs <bskeggs@redhat.com>]

On Wed, 2010-11-10 at 16:32 -0500, Andy Lutomirski wrote:
> The old code generated an interrupt storm bad enough to completely
> take down my system.
> 
> This only fixes the bits that are defined nouveau_regs.h.  Newer hardware
> uses another register that isn't described, and I don't have that hardware
> to test.
Thanks for looking at this.  I'll take a closer look at the problem
today and see what I can come up with too, that'll work with the newer
hardware too.

Ben.
> 
> Signed-off-by: Andy Lutomirski <luto@mit.edu>
> Cc: <stable@kernel.org>
> ---
>  drivers/gpu/drm/nouveau/nouveau_drv.h  |    5 +++++
>  drivers/gpu/drm/nouveau/nouveau_irq.c  |    1 +
>  drivers/gpu/drm/nouveau/nv50_display.c |   17 +++++++++++++----
>  3 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
> index b1be617..b6c62cc 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drv.h
> +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
> @@ -531,6 +531,11 @@ struct drm_nouveau_private {
>  	struct work_struct irq_work;
>  	struct work_struct hpd_work;
>  
> +	struct {
> +		spinlock_t lock;
> +		uint32_t hpd0_bits;
> +	} hpd_state;
> +
>  	struct list_head vbl_waiting;
>  
>  	struct {
> diff --git a/drivers/gpu/drm/nouveau/nouveau_irq.c b/drivers/gpu/drm/nouveau/nouveau_irq.c
> index 794b0ee..b62a601 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_irq.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_irq.c
> @@ -52,6 +52,7 @@ nouveau_irq_preinstall(struct drm_device *dev)
>  	if (dev_priv->card_type >= NV_50) {
>  		INIT_WORK(&dev_priv->irq_work, nv50_display_irq_handler_bh);
>  		INIT_WORK(&dev_priv->hpd_work, nv50_display_irq_hotplug_bh);
> +		spin_lock_init(&dev_priv->hpd_state.lock);
>  		INIT_LIST_HEAD(&dev_priv->vbl_waiting);
>  	}
>  }
> diff --git a/drivers/gpu/drm/nouveau/nv50_display.c b/drivers/gpu/drm/nouveau/nv50_display.c
> index 83a7d27..0df08e3 100644
> --- a/drivers/gpu/drm/nouveau/nv50_display.c
> +++ b/drivers/gpu/drm/nouveau/nv50_display.c
> @@ -1014,7 +1014,12 @@ nv50_display_irq_hotplug_bh(struct work_struct *work)
>  	uint32_t unplug_mask, plug_mask, change_mask;
>  	uint32_t hpd0, hpd1 = 0;
>  
> -	hpd0 = nv_rd32(dev, NV50_PCONNECTOR_HOTPLUG_CTRL) & nv_rd32(dev, NV50_PCONNECTOR_HOTPLUG_INTR);
> +	spin_lock_irq(&dev_priv->hpd_state.lock);
> +	hpd0 = dev_priv->hpd_state.hpd0_bits;
> +	dev_priv->hpd_state.hpd0_bits = 0;
> +	spin_unlock_irq(&dev_priv->hpd_state.lock);
> +
> +	hpd0 &= nv_rd32(dev, NV50_PCONNECTOR_HOTPLUG_INTR);
>  	if (dev_priv->chipset >= 0x90)
>  		hpd1 = nv_rd32(dev, 0xe074) & nv_rd32(dev, 0xe070);
>  
> @@ -1058,7 +1063,6 @@ nv50_display_irq_hotplug_bh(struct work_struct *work)
>  			helper->dpms(connector->encoder, DRM_MODE_DPMS_OFF);
>  	}
>  
> -	nv_wr32(dev, NV50_PCONNECTOR_HOTPLUG_CTRL, nv_rd32(dev, NV50_PCONNECTOR_HOTPLUG_CTRL));
>  	if (dev_priv->chipset >= 0x90)
>  		nv_wr32(dev, 0xe074, nv_rd32(dev, 0xe074));
>  
> @@ -1072,8 +1076,13 @@ nv50_display_irq_handler(struct drm_device *dev)
>  	uint32_t delayed = 0;
>  
>  	if (nv_rd32(dev, NV50_PMC_INTR_0) & NV50_PMC_INTR_0_HOTPLUG) {
> -		if (!work_pending(&dev_priv->hpd_work))
> -			queue_work(dev_priv->wq, &dev_priv->hpd_work);
> +		uint32_t hpd0_bits = nv_rd32(dev, NV50_PCONNECTOR_HOTPLUG_CTRL);
> +		nv_wr32(dev, NV50_PCONNECTOR_HOTPLUG_CTRL, hpd0_bits);
> +		spin_lock(&dev_priv->hpd_state.lock);
> +		dev_priv->hpd_state.hpd0_bits |= hpd0_bits;
> +		spin_unlock(&dev_priv->hpd_state.lock);
> +
> +		queue_work(dev_priv->wq, &dev_priv->hpd_work);
>  	}
>  
>  	while (nv_rd32(dev, NV50_PMC_INTR_0) & NV50_PMC_INTR_0_DISPLAY) {