Re: [PATCH] drm/i915: remove check for aux irq

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Apr 30, 2018 at 03:05:01PM -0700, Lucas De Marchi wrote:
> On Thu, Apr 26, 2018 at 06:50:05PM +0300, Ville Syrjälä wrote:
> > On Thu, Apr 26, 2018 at 08:42:54AM -0700, Lucas De Marchi wrote:
> > > On Thu, Apr 26, 2018 at 06:27:26PM +0300, Ville Syrjälä wrote:
> > > > On Thu, Apr 26, 2018 at 08:22:12AM -0700, Lucas De Marchi wrote:
> > > > > On Thu, Apr 26, 2018 at 04:43:38PM +0300, Ville Syrjälä wrote:
> > > > > > On Wed, Apr 25, 2018 at 02:55:24PM -0700, Lucas De Marchi wrote:
> > > > > > > This became dead code with commit 309bd8ed464f ("drm/i915: Reinstate
> > > > > > > GMBUS and AUX interrupts on gen4/g4x").
> > > > > > > 
> > > > > > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > > > > Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> > > > > > > ---
> > > > > > >  drivers/gpu/drm/i915/i915_drv.h  |  3 +--
> > > > > > >  drivers/gpu/drm/i915/intel_dp.c  | 22 +++++++---------------
> > > > > > >  drivers/gpu/drm/i915/intel_drv.h |  1 -
> > > > > > >  drivers/gpu/drm/i915/intel_psr.c |  2 +-
> > > > > > >  4 files changed, 9 insertions(+), 19 deletions(-)
> > > > > > > 
> > > > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > > > > > > index 8444ca8d5aa3..09e1c2289ea1 100644
> > > > > > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > > > > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > > > > > @@ -2545,7 +2545,7 @@ intel_info(const struct drm_i915_private *dev_priv)
> > > > > > >  	 IS_SKL_GT3(dev_priv) || IS_SKL_GT4(dev_priv))
> > > > > > >  
> > > > > > >  /*
> > > > > > > - * dp aux and gmbus irq on gen4 seems to be able to generate legacy interrupts
> > > > > > > + * gmbus irq on gen4 seems to be able to generate legacy interrupts
> > > > > > 
> > > > > > Why are you removing vital information from the comment?
> > > > > 
> > > > > Because it wouldn't match the code anymore. We always use aux irq.
> > > > 
> > > > The comment is documenting the hardware behaviour. We don't want to lose
> > > > that information.
> > > 
> > > IMO it's confusing to have the comment saying one thing and then code
> > > not following it. Reading it again I see the second paragraph you added
> > > actually document the code and the first the HW behavior. Maybe starting
> > > the second paragraph with a "However" would make it clearer.  Or I can just
> > > drop this change in the comment.
> > 
> > Or you can move the relevant parts of the comment to the place where
> > we do the "MSI or not to MSI" decision.
> 
> Humn, not sure I fully understand what you mean by relevant part. Do you
> mean something like this?
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index b7dbeba72dec..3fc6b915dac1 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1183,6 +1183,9 @@ static int i915_driver_init_hw(struct drm_i915_private *dev_priv)
>  	 * get lost on g4x as well, and interrupt delivery seems to stay
>  	 * properly dead afterwards. So we'll just disable them for all
>  	 * pre-gen5 chipsets.
> +	 *
> +	 * Since we don't enable MSI on gen <= 4 we can always use GMBUS/AUX
> +	 * interrupts.
>  	 */
>  	if (INTEL_GEN(dev_priv) >= 5) {
>  		if (pci_enable_msi(pdev) < 0)
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 09e1c2289ea1..5fd47227da23 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2545,13 +2545,10 @@ intel_info(const struct drm_i915_private *dev_priv)
>  	 IS_SKL_GT3(dev_priv) || IS_SKL_GT4(dev_priv))
>  
>  /*
> - * gmbus irq on gen4 seems to be able to generate legacy interrupts
> + * dp aux and gmbus irq on gen4 seems to be able to generate legacy interrupts
>   * even when in MSI mode. This results in spurious interrupt warnings if the
>   * legacy irq no. is shared with another device. The kernel then disables that
>   * interrupt source and so prevents the other device from working properly.

I mean all of that ^

> - *
> - * Since we don't enable MSI anymore on gen4, we can always use GMBUS/AUX
> - * interrupts.
>   */
>  #define HAS_GMBUS_IRQ(dev_priv) (INTEL_GEN(dev_priv) >= 4)
>  
> -------
> 
> It doesn't seem clearer to me.
> 
> Lucas De Marchi
> 
> 
> > 
> > -- 
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel
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