On Fri, Jan 05, 2018 at 08:59:05AM +0000, Kenneth Graunke wrote:
> Geminilake requires the 3D driver to select whether barriers are
> intended for compute shaders, or tessellation control shaders, by
> whacking a "Barrier Mode" bit in SLICE_COMMON_ECO_CHICKEN1 when
> switching pipelines. Failure to do this properly can result in GPU
> hangs.
>
> Unfortunately, this means it needs to switch mid-batch, so only
> userspace can properly set it. To facilitate this, the kernel needs
> to whitelist the register.
>
> The workarounds page currently tags this as applying to Broxton only,
> but that doesn't make sense. The documentation for the register it
> references says the bit userspace is supposed to toggle only exists on
> Geminilake. Empirically, the Mesa patch to toggle this bit appears to
> fix intermittent GPU hangs in tessellation control shader barrier tests
> on Geminilake; we haven't seen those hangs on Broxton.
I just read the bit definition and fully agree with this.
>
> v2: Mention WA #0862 in the comment (it doesn't have a name).
>
> Signed-off-by: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
> Acked-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Merged, thanks.
> ---
> drivers/gpu/drm/i915/i915_reg.h | 2 ++
> drivers/gpu/drm/i915/intel_engine_cs.c | 5 +++++
> 2 files changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 966e4df9700e..505c605eff98 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7079,6 +7079,8 @@ enum {
> #define GEN9_SLICE_COMMON_ECO_CHICKEN0 _MMIO(0x7308)
> #define DISABLE_PIXEL_MASK_CAMMING (1<<14)
>
> +#define GEN9_SLICE_COMMON_ECO_CHICKEN1 _MMIO(0x731c)
> +
> #define GEN7_L3SQCREG1 _MMIO(0xB010)
> #define VLV_B0_WA_L3SQCREG1_VALUE 0x00D30000
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index ebdcbcbacb3c..6bb51a502b8b 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -1338,6 +1338,11 @@ static int glk_init_workarounds(struct intel_engine_cs *engine)
> if (ret)
> return ret;
>
> + /* WA #0862: Userspace has to set "Barrier Mode" to avoid hangs. */
> + ret = wa_ring_whitelist_reg(engine, GEN9_SLICE_COMMON_ECO_CHICKEN1);
> + if (ret)
> + return ret;
> +
> /* WaToEnableHwFixForPushConstHWBug:glk */
> WA_SET_BIT_MASKED(COMMON_SLICE_CHICKEN2,
> GEN8_SBE_DISABLE_REPLAY_BUF_OPTIMIZATION);
> --
> 2.15.1
>