Re: [PATCH] drm/i915: Flush writes to GMBUS registers

[Jiri Kosina]

On Mon, 18 Mar 2013, Chris Wilson wrote:

> If we do not complete the writes to the GMBUS registers, they remain
> active for an indefinite period of time afterwards, even causing
> spurious interrupts on gm45.
> 
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Link: http://lkml.kernel.org/r/alpine.LNX.2.00.1303151424140.9529@xxxxxxxxxxxxx
> Cc: Shawn Starr <shawn.starr@xxxxxxxxxx>
> Cc: Jiri Kosina <jkosina@xxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>

Unfortunately I can't provide my Tested-by or Acked-by for this, as I am 
still seeing the "nobody cared" for irq 16 with this patch applied.

> ---
>  drivers/gpu/drm/i915/intel_i2c.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
> index acf8aec..ca6c17e 100644
> --- a/drivers/gpu/drm/i915/intel_i2c.c
> +++ b/drivers/gpu/drm/i915/intel_i2c.c
> @@ -64,6 +64,7 @@ intel_i2c_reset(struct drm_device *dev)
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	I915_WRITE(dev_priv->gpio_mmio_base + GMBUS0, 0);
>  	I915_WRITE(dev_priv->gpio_mmio_base + GMBUS4, 0);
> +	POSTING_READ(dev_priv->gpio_mmio_base + GMBUS4);
>  }
>  
>  static void intel_i2c_quirk_set(struct drm_i915_private *dev_priv, bool enable)
> @@ -232,6 +233,7 @@ gmbus_wait_hw_status(struct drm_i915_private *dev_priv,
>  	finish_wait(&dev_priv->gmbus_wait_queue, &wait);
>  
>  	I915_WRITE(GMBUS4 + reg_offset, 0);
> +	POSTING_READ(GMBUS4 + reg_offset);
>  
>  	if (gmbus2 & GMBUS_SATOER)
>  		return -ENXIO;
> @@ -257,6 +259,7 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv)
>  	ret = wait_event_timeout(dev_priv->gmbus_wait_queue, C, 10);
>  
>  	I915_WRITE(GMBUS4 + reg_offset, 0);
> +	POSTING_READ(GMBUS4 + reg_offset);
>  
>  	if (ret)
>  		return 0;
> @@ -486,6 +489,7 @@ timeout:
>  	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
>  
>  out:
> +	POSTING_READ(GMBUS0 + dev_priv->gpio_mmio_base);
>  	mutex_unlock(&dev_priv->gmbus_mutex);
>  	return ret;
>  }
> -- 
> 1.7.10.4
> 

-- 
Jiri Kosina
SUSE Labs
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