[Intel-gfx] [PATCH] drm/i915/cnp: Properly handle VBT ddc pin out of bounds.

[Rodrigo Vivi]

On Thu, Jan 25, 2018 at 06:07:19PM +0000, Lucas De Marchi wrote:
> On Thu, Jan 25, 2018 at 05:52:26PM +0200, Jani Nikula wrote:
> > On Thu, 25 Jan 2018, Rodrigo Vivi <rodrigo.vivi at intel.com> wrote:
> > > If the table result is out of bounds on the array map
> > > there is something really wrong with VBT pin so we don't
> > > return that vbt_pin, but only return 0 instead.
> > >
> > > This basically reverts commit 'a8e6f3888b05 ("drm/i915/cnp:
> > > Ignore VBT request for know invalid DDC pin.")'
> > >
> > > Also this properly fixes commit 9c3b2689d01f ("drm/i915/cnl:
> > > Map VBT DDC Pin to BSpec DDC Pin.")
> > >
> > > v2: Do in a way that we don't break other platforms. (Jani)
> > > v3: Keep debug message (Jani)
> > >
> > > Fixes: a8e6f3888b05 ("drm/i915/cnp: Ignore VBT request for know invalid DDC pin.")
> > > Fixes: 9c3b2689d01f ("drm/i915/cnl: Map VBT DDC Pin to BSpec DDC Pin.")
> > > Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
> > > Cc: Jani Nikula <jani.nikula at intel.com>
> > > Cc: Kai Heng Feng <kai.heng.feng at canonical.com>
> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_bios.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> > > index 95f0b310d656..06526b17a011 100644
> > > --- a/drivers/gpu/drm/i915/intel_bios.c
> > > +++ b/drivers/gpu/drm/i915/intel_bios.c
> > > @@ -1116,9 +1116,9 @@ static const u8 cnp_ddc_pin_map[] = {
> > >  static u8 map_ddc_pin(struct drm_i915_private *dev_priv, u8 vbt_pin)
> > >  {
> > >  	if (HAS_PCH_CNP(dev_priv)) {
> > > -		if (vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map))
> > > +		if (vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map)) {
> > >  			return cnp_ddc_pin_map[vbt_pin];
> > > -		if (vbt_pin > GMBUS_PIN_4_CNP) {
> > > +		} else {
> > 
> > You're going to hate me, but I just realized this will now complain
> > about vbt_pin == 0, which I guess is valid for N/A.
> > 
> > Why are simple things so hard sometimes... :(
> > 
> > else if (vbt_pin) ?
> 
> vpt_pin is unsigned so we are just special-casing the vpt_pin == 0
> already. What about stopping doing that by adding it to the array, like
> below (to be squashed)

That's a very good suggestion for the cnp part.
cleaner...

and we don't want to make cnp more difficult because of icp...
but if you also have a good idea for that icp case please raise that!

> 
> -------
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 06526b17a011..cf3f8f1ba6f7 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1107,6 +1107,7 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
>  }
>  
>  static const u8 cnp_ddc_pin_map[] = {
> +	[0] = 0, /* N/A */

N/A for Not Alternate? hehe

maybe:
+	[0] = 0, /* Per platform default */

>  	[DDC_BUS_DDI_B] = GMBUS_PIN_1_BXT,
>  	[DDC_BUS_DDI_C] = GMBUS_PIN_2_BXT,
>  	[DDC_BUS_DDI_D] = GMBUS_PIN_4_CNP, /* sic */
> @@ -1116,7 +1117,7 @@ static const u8 cnp_ddc_pin_map[] = {
>  static u8 map_ddc_pin(struct drm_i915_private *dev_priv, u8 vbt_pin)
>  {
>  	if (HAS_PCH_CNP(dev_priv)) {
> -		if (vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map)) {
> +		if (vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map)) {
>  			return cnp_ddc_pin_map[vbt_pin];
>  		} else {
>  			DRM_DEBUG_KMS("Ignoring alternate pin: VBT claims DDC pin %d, which is not valid for this platform\n", vbt_pin);
> -------
> 
> 
> Lucas De Marchi