[PATCH] drm/i915/gvt: Init PHY related registers for BXT

[Zhenyu Wang]

On 2018.09.12 13:29:26 +0800, Colin Xu wrote:
> On 9/12/18 11:07 AM, Zhenyu Wang wrote:
> > On 2018.09.12 10:19:05 +0800, Colin Xu wrote:
> > > Recent patch fixed the call trace
> > > "ERROR Port B enabled but PHY powered down? (PHY_CTL 00000000)".
> > > but introduced another similar call trace shown as:
> > > "ERROR Port C enabled but PHY powered down? (PHY_CTL 00000200)".
> > > The call trace will appear when host and guest enabled different ports,
> > > i.e. host using PORT C or neither PORT is enabled, while guest is always
> > > using PORT B as simulated by gvt. The issue is actually covered previously
> > > before the commit and reverals now when the commit do the right thing.
> > > 
> > > On BXT, some PHY registers are initialized by vbios, before i915 loaded.
> > > Later i915 will re-program some, or skip some based on the implementation.
> > > The initialized mmio for guest i915 is done by gvt, based on the snapshot
> > > taken from host. If host and guest have different PORT enabled, some
> > > DPIO PHY mmios that gvt initialized for guest i915 will not match the
> > > simualted monitor for guest, which leads to guest i915 print the calltrace
> > > when it's trying to enable PHY and PORT.
> > > 
> > > The solution is to init these DPIO PHY registers to default value, then
> > > guest i915 will program them to reasonable value based on the default
> > > powerwell table and enabled PORT. Together with the old patch, all similar
> > > call trace in guest kernel on BXT can be resolved.
> > > 
> > Nice write-up! Commit message is really meant to tell a good story,
> > this one tells it clearly. And I think this is the right approach.
> > Min, any comments?
> > 
> > > Fixes: c8ab5ac30ccc ("drm/i915/gvt: Make correct handling to vreg
> > > BXT_PHY_CTL_FAMILY")
> > Shouldn't this be on same line?
> 
> I have to split it since the checkpatch.pl script reports long line warning due to more than 80.
> Should the readability is considered prior to checkpatch result, in similar case like this one?
> Sometimes I'm struggling in chosing  whether to split into multiple lines or not..
>

If checkpatch doesn't complain, then should be ok.

-- 
Open Source Technology Center, Intel ltd.

$gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/intel-gvt-dev/attachments/20180912/82123b6e/attachment.sig>