| Message ID | 1522080721-7029-1-git-send-email-yunwei.zhang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 26/03/2018 17:12, Yunwei Zhang wrote: > WaProgramMgsrForCorrectSliceSpecificMmioReads dictate that before any MMIO > read into Slice/Subslice specific registers, MCR packet control > register(0xFDC) needs to be programmed to point to any enabled > slice/subslice pair. Otherwise, incorrect value will be returned. > > However, that means each subsequent MMIO read will be forwarded to a > specific slice/subslice combination as read is unicast. This is OK since > slice/subslice specific register values are consistent in almost all cases > across slice/subslice. There are rare occasions such as INSTDONE that this > value will be dependent on slice/subslice combo, in such cases, we need to > program 0xFDC and recover this after. This is already covered by > read_subslice_reg. > > Also, 0xFDC will lose its information after TDR/engine reset/power state > change. > > Reference: HSD#1405586840 BSID#0575 > > v2: > - use fls() instead of find_last_bit() (Chris) > - added INTEL_SSEU to extract sseu from device info. (Chris) > v3: > - rebase on latest tip > v4: > - Added references (Mika) > > Signed-off-by: Yunwei Zhang <yunwei.zhang@intel.com> > Cc: Oscar Mateo <oscar.mateo@intel.com> > Cc: Michel Thierry <michel.thierry@intel.com> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> > Cc: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> > --- > drivers/gpu/drm/i915/i915_drv.h | 1 + > drivers/gpu/drm/i915/intel_engine_cs.c | 39 ++++++++++++++++++++++++++++++++-- > 2 files changed, 38 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 800230b..2db2a04 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -2297,6 +2297,7 @@ intel_info(const struct drm_i915_private *dev_priv) > > #define INTEL_GEN(dev_priv) ((dev_priv)->info.gen) > #define INTEL_DEVID(dev_priv) ((dev_priv)->info.device_id) > +#define INTEL_SSEU(dev_priv) ((dev_priv)->info.sseu) If we add this someone gets the job of converting existing users? > > #define REVID_FOREVER 0xff > #define INTEL_REVID(dev_priv) ((dev_priv)->drm.pdev->revision) > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c > index de09fa4..cc19e0a 100644 > --- a/drivers/gpu/drm/i915/intel_engine_cs.c > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c > @@ -796,6 +796,27 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type) > } > } > > +static u32 calculate_mcr(u32 mcr, struct drm_i915_private *dev_priv) dev_priv first would be more typical function argument order. > +{ > + const struct sseu_dev_info *sseu = &(INTEL_SSEU(dev_priv)); > + u32 slice = fls(sseu->slice_mask); > + u32 subslice = fls(sseu->subslice_mask[slice]); > + > + mcr &= ~(GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK); > + mcr |= GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice); > + > + return mcr; > +} > + > +static void wa_init_mcr(struct drm_i915_private *dev_priv) > +{ > + u32 mcr; > + > + mcr = I915_READ(GEN8_MCR_SELECTOR); > + mcr = calculate_mcr(mcr, dev_priv); > + I915_WRITE(GEN8_MCR_SELECTOR, mcr); > +} > + > static inline uint32_t > read_subslice_reg(struct drm_i915_private *dev_priv, int slice, > int subslice, i915_reg_t reg) > @@ -828,18 +849,29 @@ read_subslice_reg(struct drm_i915_private *dev_priv, int slice, > intel_uncore_forcewake_get__locked(dev_priv, fw_domains); > > mcr = I915_READ_FW(GEN8_MCR_SELECTOR); > + > /* > * The HW expects the slice and sublice selectors to be reset to 0 > * after reading out the registers. > */ > - WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); > + if (INTEL_GEN(dev_priv) < 10) > + WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); Can squash to single line WARN_ON_ONCE(INTEL_GEN() < 10 && (mcr & ...)), if it fits. > mcr &= ~mcr_slice_subslice_mask; > mcr |= mcr_slice_subslice_select; > I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); > > ret = I915_READ_FW(reg); > > - mcr &= ~mcr_slice_subslice_mask; > + /* > + * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl > + * expects mcr to be programed to a enabled slice/subslice pair > + * before any MMIO read into slice/subslice register > + */ > + if (INTEL_GEN(dev_priv) < 10) > + mcr &= ~mcr_slice_subslice_mask; > + else > + mcr = calculate_mcr(mcr, dev_priv); Does it make sense to move the conditional and comment to calculate_mcr - so here only a single call to it remains? > + > I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); > > intel_uncore_forcewake_put__locked(dev_priv, fw_domains); > @@ -1307,6 +1339,9 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine) > struct drm_i915_private *dev_priv = engine->i915; > int ret; > > + /* WaProgramMgsrForCorrectSliceSpecificMmioReads: cnl */ > + wa_init_mcr(dev_priv); > + > /* WaDisableI2mCycleOnWRPort:cnl (pre-prod) */ > if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0)) > I915_WRITE(GAMT_CHKN_BIT_REG, > Above are suggestions and questions only. Regards, Tvrtko
Yunwei Zhang <yunwei.zhang@intel.com> writes: > WaProgramMgsrForCorrectSliceSpecificMmioReads dictate that before any MMIO > read into Slice/Subslice specific registers, MCR packet control > register(0xFDC) needs to be programmed to point to any enabled > slice/subslice pair. Otherwise, incorrect value will be returned. > > However, that means each subsequent MMIO read will be forwarded to a > specific slice/subslice combination as read is unicast. This is OK since > slice/subslice specific register values are consistent in almost all cases > across slice/subslice. There are rare occasions such as INSTDONE that this > value will be dependent on slice/subslice combo, in such cases, we need to > program 0xFDC and recover this after. This is already covered by > read_subslice_reg. > > Also, 0xFDC will lose its information after TDR/engine reset/power state > change. > > Reference: HSD#1405586840 BSID#0575 Use plural, and add comma in between. Move 'References' right before Cc:s after the version log... > > v2: > - use fls() instead of find_last_bit() (Chris) > - added INTEL_SSEU to extract sseu from device info. (Chris) > v3: > - rebase on latest tip > v4: > - Added references (Mika) > .. in here. And we usually do put Cc:s before s-o-b. For example, see commit 465418c6064c88d4af555abe0480c417eb47eae3 Thanks, -Mika > Signed-off-by: Yunwei Zhang <yunwei.zhang@intel.com> > Cc: Oscar Mateo <oscar.mateo@intel.com> > Cc: Michel Thierry <michel.thierry@intel.com> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> > Cc: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> > --- > drivers/gpu/drm/i915/i915_drv.h | 1 + > drivers/gpu/drm/i915/intel_engine_cs.c | 39 ++++++++++++++++++++++++++++++++-- > 2 files changed, 38 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 800230b..2db2a04 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -2297,6 +2297,7 @@ intel_info(const struct drm_i915_private *dev_priv) > > #define INTEL_GEN(dev_priv) ((dev_priv)->info.gen) > #define INTEL_DEVID(dev_priv) ((dev_priv)->info.device_id) > +#define INTEL_SSEU(dev_priv) ((dev_priv)->info.sseu) > > #define REVID_FOREVER 0xff > #define INTEL_REVID(dev_priv) ((dev_priv)->drm.pdev->revision) > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c > index de09fa4..cc19e0a 100644 > --- a/drivers/gpu/drm/i915/intel_engine_cs.c > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c > @@ -796,6 +796,27 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type) > } > } > > +static u32 calculate_mcr(u32 mcr, struct drm_i915_private *dev_priv) > +{ > + const struct sseu_dev_info *sseu = &(INTEL_SSEU(dev_priv)); > + u32 slice = fls(sseu->slice_mask); > + u32 subslice = fls(sseu->subslice_mask[slice]); > + > + mcr &= ~(GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK); > + mcr |= GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice); > + > + return mcr; > +} > + > +static void wa_init_mcr(struct drm_i915_private *dev_priv) > +{ > + u32 mcr; > + > + mcr = I915_READ(GEN8_MCR_SELECTOR); > + mcr = calculate_mcr(mcr, dev_priv); > + I915_WRITE(GEN8_MCR_SELECTOR, mcr); > +} > + > static inline uint32_t > read_subslice_reg(struct drm_i915_private *dev_priv, int slice, > int subslice, i915_reg_t reg) > @@ -828,18 +849,29 @@ read_subslice_reg(struct drm_i915_private *dev_priv, int slice, > intel_uncore_forcewake_get__locked(dev_priv, fw_domains); > > mcr = I915_READ_FW(GEN8_MCR_SELECTOR); > + > /* > * The HW expects the slice and sublice selectors to be reset to 0 > * after reading out the registers. > */ > - WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); > + if (INTEL_GEN(dev_priv) < 10) > + WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); > mcr &= ~mcr_slice_subslice_mask; > mcr |= mcr_slice_subslice_select; > I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); > > ret = I915_READ_FW(reg); > > - mcr &= ~mcr_slice_subslice_mask; > + /* > + * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl > + * expects mcr to be programed to a enabled slice/subslice pair > + * before any MMIO read into slice/subslice register > + */ > + if (INTEL_GEN(dev_priv) < 10) > + mcr &= ~mcr_slice_subslice_mask; > + else > + mcr = calculate_mcr(mcr, dev_priv); > + > I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); > > intel_uncore_forcewake_put__locked(dev_priv, fw_domains); > @@ -1307,6 +1339,9 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine) > struct drm_i915_private *dev_priv = engine->i915; > int ret; > > + /* WaProgramMgsrForCorrectSliceSpecificMmioReads: cnl */ > + wa_init_mcr(dev_priv); > + > /* WaDisableI2mCycleOnWRPort:cnl (pre-prod) */ > if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0)) > I915_WRITE(GAMT_CHKN_BIT_REG, > -- > 2.7.4
Quoting Tvrtko Ursulin (2018-03-26 17:57:38) > > On 26/03/2018 17:12, Yunwei Zhang wrote: > > --- > > drivers/gpu/drm/i915/i915_drv.h | 1 + > > drivers/gpu/drm/i915/intel_engine_cs.c | 39 ++++++++++++++++++++++++++++++++-- > > 2 files changed, 38 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > > index 800230b..2db2a04 100644 > > --- a/drivers/gpu/drm/i915/i915_drv.h > > +++ b/drivers/gpu/drm/i915/i915_drv.h > > @@ -2297,6 +2297,7 @@ intel_info(const struct drm_i915_private *dev_priv) > > > > #define INTEL_GEN(dev_priv) ((dev_priv)->info.gen) > > #define INTEL_DEVID(dev_priv) ((dev_priv)->info.device_id) > > +#define INTEL_SSEU(dev_priv) ((dev_priv)->info.sseu) > > If we add this someone gets the job of converting existing users? My bad, I hadn't realised that the INTEL_SSEU conversion was local to my tree. It must have fallen out as part of the static device_info reform. -Chris
On 3/26/2018 9:57 AM, Tvrtko Ursulin wrote: > > On 26/03/2018 17:12, Yunwei Zhang wrote: >> WaProgramMgsrForCorrectSliceSpecificMmioReads dictate that before any >> MMIO >> read into Slice/Subslice specific registers, MCR packet control >> register(0xFDC) needs to be programmed to point to any enabled >> slice/subslice pair. Otherwise, incorrect value will be returned. >> >> However, that means each subsequent MMIO read will be forwarded to a >> specific slice/subslice combination as read is unicast. This is OK since >> slice/subslice specific register values are consistent in almost all >> cases >> across slice/subslice. There are rare occasions such as INSTDONE that >> this >> value will be dependent on slice/subslice combo, in such cases, we >> need to >> program 0xFDC and recover this after. This is already covered by >> read_subslice_reg. >> >> Also, 0xFDC will lose its information after TDR/engine reset/power state >> change. >> >> Reference: HSD#1405586840 BSID#0575 >> >> v2: >> - use fls() instead of find_last_bit() (Chris) >> - added INTEL_SSEU to extract sseu from device info. (Chris) >> v3: >> - rebase on latest tip >> v4: >> - Added references (Mika) >> >> Signed-off-by: Yunwei Zhang <yunwei.zhang@intel.com> >> Cc: Oscar Mateo <oscar.mateo@intel.com> >> Cc: Michel Thierry <michel.thierry@intel.com> >> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> >> Cc: Chris Wilson <chris@chris-wilson.co.uk> >> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> >> --- >> drivers/gpu/drm/i915/i915_drv.h | 1 + >> drivers/gpu/drm/i915/intel_engine_cs.c | 39 >> ++++++++++++++++++++++++++++++++-- >> 2 files changed, 38 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/i915_drv.h >> b/drivers/gpu/drm/i915/i915_drv.h >> index 800230b..2db2a04 100644 >> --- a/drivers/gpu/drm/i915/i915_drv.h >> +++ b/drivers/gpu/drm/i915/i915_drv.h >> @@ -2297,6 +2297,7 @@ intel_info(const struct drm_i915_private >> *dev_priv) >> #define INTEL_GEN(dev_priv) ((dev_priv)->info.gen) >> #define INTEL_DEVID(dev_priv) ((dev_priv)->info.device_id) >> +#define INTEL_SSEU(dev_priv) ((dev_priv)->info.sseu) > > If we add this someone gets the job of converting existing users? This is suggestion from Chris Wilson, I am new here, but I guess if I am going to do that, it is better in a separate patch. I will remove this in next patchset and submit a new patch later. >> #define REVID_FOREVER 0xff >> #define INTEL_REVID(dev_priv) ((dev_priv)->drm.pdev->revision) >> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c >> b/drivers/gpu/drm/i915/intel_engine_cs.c >> index de09fa4..cc19e0a 100644 >> --- a/drivers/gpu/drm/i915/intel_engine_cs.c >> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c >> @@ -796,6 +796,27 @@ const char *i915_cache_level_str(struct >> drm_i915_private *i915, int type) >> } >> } >> +static u32 calculate_mcr(u32 mcr, struct drm_i915_private *dev_priv) > > dev_priv first would be more typical function argument order. > >> +{ >> + const struct sseu_dev_info *sseu = &(INTEL_SSEU(dev_priv)); >> + u32 slice = fls(sseu->slice_mask); >> + u32 subslice = fls(sseu->subslice_mask[slice]); >> + >> + mcr &= ~(GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK); >> + mcr |= GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice); >> + >> + return mcr; >> +} >> + >> +static void wa_init_mcr(struct drm_i915_private *dev_priv) >> +{ >> + u32 mcr; >> + >> + mcr = I915_READ(GEN8_MCR_SELECTOR); >> + mcr = calculate_mcr(mcr, dev_priv); >> + I915_WRITE(GEN8_MCR_SELECTOR, mcr); >> +} >> + >> static inline uint32_t >> read_subslice_reg(struct drm_i915_private *dev_priv, int slice, >> int subslice, i915_reg_t reg) >> @@ -828,18 +849,29 @@ read_subslice_reg(struct drm_i915_private >> *dev_priv, int slice, >> intel_uncore_forcewake_get__locked(dev_priv, fw_domains); >> mcr = I915_READ_FW(GEN8_MCR_SELECTOR); >> + >> /* >> * The HW expects the slice and sublice selectors to be reset to 0 >> * after reading out the registers. >> */ >> - WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); >> + if (INTEL_GEN(dev_priv) < 10) >> + WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); > > Can squash to single line WARN_ON_ONCE(INTEL_GEN() < 10 && (mcr & > ...)), if it fits. > >> mcr &= ~mcr_slice_subslice_mask; >> mcr |= mcr_slice_subslice_select; >> I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); >> ret = I915_READ_FW(reg); >> - mcr &= ~mcr_slice_subslice_mask; >> + /* >> + * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl >> + * expects mcr to be programed to a enabled slice/subslice pair >> + * before any MMIO read into slice/subslice register >> + */ >> + if (INTEL_GEN(dev_priv) < 10) >> + mcr &= ~mcr_slice_subslice_mask; >> + else >> + mcr = calculate_mcr(mcr, dev_priv); > > Does it make sense to move the conditional and comment to > calculate_mcr - so here only a single call to it remains? I am thinking maybe it is better to save jump/return for GENs that don't have WA.. >> + >> I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); >> intel_uncore_forcewake_put__locked(dev_priv, fw_domains); >> @@ -1307,6 +1339,9 @@ static int cnl_init_workarounds(struct >> intel_engine_cs *engine) >> struct drm_i915_private *dev_priv = engine->i915; >> int ret; >> + /* WaProgramMgsrForCorrectSliceSpecificMmioReads: cnl */ >> + wa_init_mcr(dev_priv); >> + >> /* WaDisableI2mCycleOnWRPort:cnl (pre-prod) */ >> if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0)) >> I915_WRITE(GAMT_CHKN_BIT_REG, >> > > Above are suggestions and questions only. > > Regards, > > Tvrtko
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 800230b..2db2a04 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2297,6 +2297,7 @@ intel_info(const struct drm_i915_private *dev_priv) #define INTEL_GEN(dev_priv) ((dev_priv)->info.gen) #define INTEL_DEVID(dev_priv) ((dev_priv)->info.device_id) +#define INTEL_SSEU(dev_priv) ((dev_priv)->info.sseu) #define REVID_FOREVER 0xff #define INTEL_REVID(dev_priv) ((dev_priv)->drm.pdev->revision) diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c index de09fa4..cc19e0a 100644 --- a/drivers/gpu/drm/i915/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/intel_engine_cs.c @@ -796,6 +796,27 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type) } } +static u32 calculate_mcr(u32 mcr, struct drm_i915_private *dev_priv) +{ + const struct sseu_dev_info *sseu = &(INTEL_SSEU(dev_priv)); + u32 slice = fls(sseu->slice_mask); + u32 subslice = fls(sseu->subslice_mask[slice]); + + mcr &= ~(GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK); + mcr |= GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice); + + return mcr; +} + +static void wa_init_mcr(struct drm_i915_private *dev_priv) +{ + u32 mcr; + + mcr = I915_READ(GEN8_MCR_SELECTOR); + mcr = calculate_mcr(mcr, dev_priv); + I915_WRITE(GEN8_MCR_SELECTOR, mcr); +} + static inline uint32_t read_subslice_reg(struct drm_i915_private *dev_priv, int slice, int subslice, i915_reg_t reg) @@ -828,18 +849,29 @@ read_subslice_reg(struct drm_i915_private *dev_priv, int slice, intel_uncore_forcewake_get__locked(dev_priv, fw_domains); mcr = I915_READ_FW(GEN8_MCR_SELECTOR); + /* * The HW expects the slice and sublice selectors to be reset to 0 * after reading out the registers. */ - WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); + if (INTEL_GEN(dev_priv) < 10) + WARN_ON_ONCE(mcr & mcr_slice_subslice_mask); mcr &= ~mcr_slice_subslice_mask; mcr |= mcr_slice_subslice_select; I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); ret = I915_READ_FW(reg); - mcr &= ~mcr_slice_subslice_mask; + /* + * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl + * expects mcr to be programed to a enabled slice/subslice pair + * before any MMIO read into slice/subslice register + */ + if (INTEL_GEN(dev_priv) < 10) + mcr &= ~mcr_slice_subslice_mask; + else + mcr = calculate_mcr(mcr, dev_priv); + I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr); intel_uncore_forcewake_put__locked(dev_priv, fw_domains); @@ -1307,6 +1339,9 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine) struct drm_i915_private *dev_priv = engine->i915; int ret; + /* WaProgramMgsrForCorrectSliceSpecificMmioReads: cnl */ + wa_init_mcr(dev_priv); + /* WaDisableI2mCycleOnWRPort:cnl (pre-prod) */ if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0)) I915_WRITE(GAMT_CHKN_BIT_REG,
WaProgramMgsrForCorrectSliceSpecificMmioReads dictate that before any MMIO read into Slice/Subslice specific registers, MCR packet control register(0xFDC) needs to be programmed to point to any enabled slice/subslice pair. Otherwise, incorrect value will be returned. However, that means each subsequent MMIO read will be forwarded to a specific slice/subslice combination as read is unicast. This is OK since slice/subslice specific register values are consistent in almost all cases across slice/subslice. There are rare occasions such as INSTDONE that this value will be dependent on slice/subslice combo, in such cases, we need to program 0xFDC and recover this after. This is already covered by read_subslice_reg. Also, 0xFDC will lose its information after TDR/engine reset/power state change. Reference: HSD#1405586840 BSID#0575 v2: - use fls() instead of find_last_bit() (Chris) - added INTEL_SSEU to extract sseu from device info. (Chris) v3: - rebase on latest tip v4: - Added references (Mika) Signed-off-by: Yunwei Zhang <yunwei.zhang@intel.com> Cc: Oscar Mateo <oscar.mateo@intel.com> Cc: Michel Thierry <michel.thierry@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> --- drivers/gpu/drm/i915/i915_drv.h | 1 + drivers/gpu/drm/i915/intel_engine_cs.c | 39 ++++++++++++++++++++++++++++++++-- 2 files changed, 38 insertions(+), 2 deletions(-)