[Intel-gfx] [PATCH] drm/i915: Move skl/bxt gt specific workarounds to ring init

[Chris Wilson]

On Mon, Oct 12, 2015 at 01:20:59PM +0300, Mika Kuoppala wrote:
> Some registers are, naturally, lost in gpu reset/suspend cycle.
> And some registers, for example in display domain, are not subject
> to gpu reset so they retain their contents.
> 
> As hang recovery triggers a reset, recoverable gpu hang can currently
> flush out essential workarounds and cause havoc later on.
> 
> When register GEN8_GARBNTL is missing the WaEnableGapsTsvCreditFix:skl,
> it can cause random system hangs [1]. This workaround was added in:
> commit 245d96670d26 ("drm/i915:skl: Add WaEnableGapsTsvCreditFix")
> But another set of system hangs were observed and the failure pattern
> indicated that there was random gpu hang preceding the system hang [2].
> This lead to the realization that we lose this workaround and BDW_SCRATCH1
> on reset.
> 
> Add these workarounds setup in display init to skl/bxt ring init
> where LRI workarounds are also setup. This way their setup is not
> dependent on display side init.
> 
> References: [1] https://bugs.freedesktop.org/show_bug.cgi?id=90854
> References: [2] https://bugs.freedesktop.org/show_bug.cgi?id=92315
> Reported-by: Tomi Sarvela <tomix.p.sarvela at intel.com>
> Cc: Tomi Sarvela <tomix.p.sarvela at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>

I had forgotten we had begun splitting out the GT registers from the
display registers for init_hw. These movements make sense so,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre