[Intel-gfx] [PATCH 15/15] drm/i915/xehp: Eliminate shared/implicit steering
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Fri Apr 1 08:34:04 UTC 2022
On 31/03/2022 00:28, Matt Roper wrote:
> Historically we've selected and programmed a single MCR group/instance
> ID at driver startup that will steer register accesses for GSLICE/DSS
> ranges to a non-terminated instance. Any reads of these register ranges
> that don't need a specific unicast access won't bother explicitly
> resteering because the control register should already be set to a
> suitable value to receive a non-terminated response. Any accesses to
> other types of MCR ranges (MSLICE, LNCF, etc.) that are also satisfied
> by the default steering target will also skip explicit re-steering at
> runtime.
>
> This approach has worked well for many years and many platforms, but our
> hardware teams have recently advised us that they're not 100%
> comfortable with our strategy going forward. They now suggest
> explicitly steering reads of any multicast register at the time the
> register access happens rather than relying on previously-programmed
> steering values. In debug settings there could be external agents that
> have adjusted the default steering without the driver's knowledge (e.g.,
> we could do this manually with IGT's intel_reg today, although the
> hardware teams also have other tools they use for debug and analysis).
> In theory it would also be possible for bad firmware and/or incorrect
> handling of power management events to clobber/wipe the steering
> value we had previously initialized because they assume we'll be
> re-programming it anyway.
>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_gt_mcr.c | 40 +++++++++
> drivers/gpu/drm/i915/gt/intel_gt_types.h | 1 +
> drivers/gpu/drm/i915/gt/intel_workarounds.c | 98 ++++-----------------
> 3 files changed, 56 insertions(+), 83 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> index a9a9fa6881f2..787752367337 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> @@ -35,6 +35,7 @@
> */
>
> static const char * const intel_steering_types[] = {
> + "GSLICE/DSS",
> "L3BANK",
> "MSLICE",
> "LNCF",
> @@ -45,6 +46,35 @@ static const struct intel_mmio_range icl_l3bank_steering_table[] = {
> {},
> };
>
> +static const struct intel_mmio_range xehpsdv_dss_steering_table[] = {
> + { 0x005200, 0x0052FF },
> + { 0x005400, 0x007FFF },
> + { 0x008140, 0x00815F },
> + { 0x008D00, 0x008DFF },
> + { 0x0094D0, 0x00955F },
> + { 0x009680, 0x0096FF },
> + { 0x00DC00, 0x00DCFF },
> + { 0x00DE80, 0x00E8FF },
> + { 0x017000, 0x017FFF },
> + { 0x024A00, 0x024A7F },
> + {},
> +};
> +
> +static const struct intel_mmio_range dg2_dss_steering_table[] = {
> + { 0x005200, 0x0052FF },
> + { 0x005400, 0x007FFF },
> + { 0x008140, 0x00815F },
> + { 0x008D00, 0x008DFF },
> + { 0x0094D0, 0x00955F },
> + { 0x009680, 0x0096FF },
> + { 0x00D800, 0x00D87F },
> + { 0x00DC00, 0x00DCFF },
> + { 0x00DE80, 0x00E8FF },
> + { 0x017000, 0x017FFF },
> + { 0x024A00, 0x024A7F },
> + {},
> +};
> +
> static const struct intel_mmio_range xehpsdv_mslice_steering_table[] = {
> { 0x004000, 0x004AFF },
> { 0x00C800, 0x00CFFF },
> @@ -87,9 +117,11 @@ void intel_gt_mcr_init(struct intel_gt *gt)
> GEN12_MEML3_EN_MASK);
>
> if (IS_DG2(i915)) {
> + gt->steering_table[DSS] = dg2_dss_steering_table;
> gt->steering_table[MSLICE] = xehpsdv_mslice_steering_table;
> gt->steering_table[LNCF] = dg2_lncf_steering_table;
> } else if (IS_XEHPSDV(i915)) {
> + gt->steering_table[DSS] = xehpsdv_dss_steering_table;
> gt->steering_table[MSLICE] = xehpsdv_mslice_steering_table;
> gt->steering_table[LNCF] = xehpsdv_lncf_steering_table;
> } else if (GRAPHICS_VER(i915) >= 11 &&
> @@ -317,7 +349,15 @@ static void get_valid_steering(struct intel_gt *gt,
> enum intel_steering_type type,
> u8 *group, u8 *instance)
> {
> + u32 dssmask = intel_sseu_get_subslices(>->info.sseu, 0);
> +
> switch (type) {
> + case DSS:
> + drm_WARN_ON(>->i915->drm, dssmask == 0);
> +
> + *group = __ffs(dssmask) / GEN_DSS_PER_GSLICE;
> + *instance = __ffs(dssmask) % GEN_DSS_PER_GSLICE;
> + break;
> case L3BANK:
> GEM_DEBUG_WARN_ON(!gt->info.l3bank_mask); /* should be impossible! */
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> index 937b2e1a305e..b77bbaac7622 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> @@ -54,6 +54,7 @@ struct intel_mmio_range {
> * are listed here.
> */
> enum intel_steering_type {
> + DSS,
> L3BANK,
> MSLICE,
> LNCF,
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index 818ba71f4909..2486c6aa9d9d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -1160,87 +1160,6 @@ icl_wa_init_mcr(struct intel_gt *gt, struct i915_wa_list *wal)
> __add_mcr_wa(gt, wal, slice, subslice);
> }
>
> -static void
> -xehp_init_mcr(struct intel_gt *gt, struct i915_wa_list *wal)
> -{
> - const struct sseu_dev_info *sseu = >->info.sseu;
> - unsigned long slice, subslice = 0, slice_mask = 0;
> - u64 dss_mask = 0;
> - u32 lncf_mask = 0;
> - int i;
> -
> - /*
> - * On Xe_HP the steering increases in complexity. There are now several
> - * more units that require steering and we're not guaranteed to be able
> - * to find a common setting for all of them. These are:
> - * - GSLICE (fusable)
> - * - DSS (sub-unit within gslice; fusable)
> - * - L3 Bank (fusable)
> - * - MSLICE (fusable)
> - * - LNCF (sub-unit within mslice; always present if mslice is present)
> - *
> - * We'll do our default/implicit steering based on GSLICE (in the
> - * sliceid field) and DSS (in the subsliceid field). If we can
> - * find overlap between the valid MSLICE and/or LNCF values with
> - * a suitable GSLICE, then we can just re-use the default value and
> - * skip and explicit steering at runtime.
> - *
> - * We only need to look for overlap between GSLICE/MSLICE/LNCF to find
> - * a valid sliceid value. DSS steering is the only type of steering
> - * that utilizes the 'subsliceid' bits.
> - *
> - * Also note that, even though the steering domain is called "GSlice"
> - * and it is encoded in the register using the gslice format, the spec
> - * says that the combined (geometry | compute) fuse should be used to
> - * select the steering.
> - */
> -
> - /* Find the potential gslice candidates */
> - dss_mask = intel_sseu_get_subslices(sseu, 0);
> - slice_mask = intel_slicemask_from_dssmask(dss_mask, GEN_DSS_PER_GSLICE);
> -
> - /*
> - * Find the potential LNCF candidates. Either LNCF within a valid
> - * mslice is fine.
> - */
> - for_each_set_bit(i, >->info.mslice_mask, GEN12_MAX_MSLICES)
> - lncf_mask |= (0x3 << (i * 2));
> -
> - /*
> - * Are there any sliceid values that work for both GSLICE and LNCF
> - * steering?
> - */
> - if (slice_mask & lncf_mask) {
> - slice_mask &= lncf_mask;
> - gt->steering_table[LNCF] = NULL;
> - }
> -
> - /* How about sliceid values that also work for MSLICE steering? */
> - if (slice_mask & gt->info.mslice_mask) {
> - slice_mask &= gt->info.mslice_mask;
> - gt->steering_table[MSLICE] = NULL;
> - }
> -
> - slice = __ffs(slice_mask);
> - subslice = __ffs(dss_mask >> (slice * GEN_DSS_PER_GSLICE));
> - WARN_ON(subslice > GEN_DSS_PER_GSLICE);
> - WARN_ON(dss_mask >> (slice * GEN_DSS_PER_GSLICE) == 0);
> -
> - __add_mcr_wa(gt, wal, slice, subslice);
> -
> - /*
> - * SQIDI ranges are special because they use different steering
> - * registers than everything else we work with. On XeHP SDV and
> - * DG2-G10, any value in the steering registers will work fine since
> - * all instances are present, but DG2-G11 only has SQIDI instances at
> - * ID's 2 and 3, so we need to steer to one of those. For simplicity
> - * we'll just steer to a hardcoded "2" since that value will work
> - * everywhere.
> - */
> - __set_mcr_steering(wal, MCFG_MCR_SELECTOR, 0, 2);
> - __set_mcr_steering(wal, SF_MCR_SELECTOR, 0, 2);
> -}
> -
> static void
> icl_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> {
> @@ -1388,8 +1307,9 @@ static void
> xehpsdv_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> {
> struct drm_i915_private *i915 = gt->i915;
> + struct drm_printer p = drm_debug_printer("MCR Steering:");
>
> - xehp_init_mcr(gt, wal);
> + intel_gt_mcr_report_steering(&p, gt, false);
>
> /* Wa_1409757795:xehpsdv */
> wa_mcr_write_or(wal, SCCGCTL94DC, CG3DDISURB);
> @@ -1441,10 +1361,22 @@ xehpsdv_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> static void
> dg2_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> {
> + struct drm_printer p = drm_debug_printer("MCR Steering:");
> struct intel_engine_cs *engine;
> int id;
>
> - xehp_init_mcr(gt, wal);
> + intel_gt_mcr_report_steering(&p, gt, false);
Are these platforms immune to system hangs caused by incorrect/missing
default MCR configuration such was fixed with c7d561cfcf86 ("drm/i915:
Enable WaProgramMgsrForCorrectSliceSpecificMmioReads for Gen9") ? That
was triggerable from userspace to be clear.
Regards,
Tvrtko
> +
> + /*
> + * SQIDI ranges are special because they use different steering
> + * registers than everything else we work with. On DG2-G10, any value
> + * in the steering registers will work fine since all instances are
> + * present, but DG2-G11 only has SQIDI instances at ID's 2 and 3, so we
> + * need to steer to one of those. For simplicity we'll just steer to a
> + * hardcoded "2" since that value will work everywhere.
> + */
> + __set_mcr_steering(wal, MCFG_MCR_SELECTOR, 0, 2);
> + __set_mcr_steering(wal, SF_MCR_SELECTOR, 0, 2);
>
> /* Wa_14011060649:dg2 */
> wa_14011060649(gt, wal);
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