Re: [Intel-gfx] [PATCH 04/12] drm/i915/bios: limit default outputs to ports A through F

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 17 Feb 2021, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
> On Wed, Feb 17, 2021 at 09:49:57PM +0200, Jani Nikula wrote:
>>On Wed, 17 Feb 2021, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
>>> On Wed, Feb 17, 2021 at 09:23:00AM -0800, Lucas De Marchi wrote:
>>>>On Wed, Feb 17, 2021 at 07:03:34PM +0200, Jani Nikula wrote:
>>>>>With the defaults limited to non-TypeC ports in commit 828ccb31cf41
>>>>>("drm/i915/icl: Add TypeC ports only if VBT is present"), this should be
>>>>>a no-op, but clarifies the code and prepares for subsequent changes.
>>>>>
>>>>>Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>>>>>Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>>>Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>>>>---
>>>>>drivers/gpu/drm/i915/display/intel_bios.c | 3 ++-
>>>>>1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>>diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>>>>>index e9cb15aa2f5a..b9d99324d66d 100644
>>>>>--- a/drivers/gpu/drm/i915/display/intel_bios.c
>>>>>+++ b/drivers/gpu/drm/i915/display/intel_bios.c
>>>>>@@ -2057,11 +2057,12 @@ static void
>>>>>init_vbt_missing_defaults(struct drm_i915_private *i915)
>>>>>{
>>>>>	enum port port;
>>>>>+	int ports = PORT_A | PORT_B | PORT_C | PORT_D | PORT_E | PORT_F;
>>>>
>>>>
>>>>I'd not spread the knowledge of what port uses tc phy like this.
>>>>It's painful to maintain.
>>
>>Umm, this wasn't meant to have anything to do with tc, really. Granted,
>>the commit message is misleading.
>
> ok, makes more sense now. I don't want us to keep updating this function
> when the ports change on new platforms.

Agreed.

>
>>
>>>
>>> also, not sure how this clarifies things if PORT_TC1 aliases PORT_D,
>>> so I'd just drop this patch
>>
>>The point is that I'd like to reduce the number of ports set up by
>>default, perhaps even further than this. It's a bit silly to generate 9
>>dummy child devices on certain platforms when there's no VBT.
>
> ok. So what would be the devices without vbt? I remember relying on this
> for e.g. dg1 before we could read it.

If it were just for enabling, I'd start some igt tool to generate a
basic VBT to use with i915.vbt_firmware and the firmware loader. It's
the existing products that ended up depending on the defaults that are
the real issue I think.

> What other platforms should we care about? And for those, should we
> really care about ports E and F or could we reduce it to, say the first
> 4?

IIRC they were some Haswell or Broadwell era Chromebooks. They probably
don't use very many ports, but in theory it could be A-D,F on DDI
platforms (E requires VBT child device). On gen 11 it could be A-E, with
F requiring VBT child device.

A-F covers all cases, but does not try to create G-I or any further
future ports.


BR,
Jani.


>
> thanks
> Lucas De Marchi
>
>>
>>
>>BR,
>>Jani.
>>
>>>
>>> Lucas De Marchi
>>>
>>>>Lucas De Marchi
>>>>
>>>>>
>>>>>	if (!HAS_DDI(i915) && !IS_CHERRYVIEW(i915))
>>>>>		return;
>>>>>
>>>>>-	for_each_port(port) {
>>>>>+	for_each_port_masked(port, ports) {
>>>>>		struct ddi_vbt_port_info *info =
>>>>>			&i915->vbt.ddi_port_info[port];
>>>>>		enum phy phy = intel_port_to_phy(i915, port);
>>>>>--
>>>>>2.20.1
>>>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>>-- 
>>Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center
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