[Intel-xe] [RFC v2 2/6] drm/xe/xe2: Determine bios enablement for flat ccs on igfx.

[Matthew Auld]

On Thu, 23 Nov 2023 at 16:37, Matthew Auld
<matthew.william.auld at gmail.com> wrote:
>
> On Tue, 21 Nov 2023 at 10:01, Himal Prasad Ghimiray
> <himal.prasad.ghimiray at intel.com> wrote:
> >
> > If bios disables flat ccs on igfx  make has_flat_ccs as 0 and notify
> > via drm_info.
> >
> > Bspec:59255
> >
> > Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
>
> Huh, I wonder if that explains why on some particular LNL DUTs
> compression just didn't seem to "work" for me.
>
> So should this information be passed along to userspace via some query
> uAPI? Maybe there is some tradeoff between enabling compression and
> other features (like coherency), and so knowing this might be useful?

Another idea might be to reject any compressed pat_index, if the
platform doesn't support flat_ccs?

>
> > ---
> >  drivers/gpu/drm/xe/regs/xe_gt_regs.h |  3 +++
> >  drivers/gpu/drm/xe/xe_device.c       | 30 ++++++++++++++++++++++++++++
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/xe/regs/xe_gt_regs.h b/drivers/gpu/drm/xe/regs/xe_gt_regs.h
> > index cc27fe8fc363..b642301947f5 100644
> > --- a/drivers/gpu/drm/xe/regs/xe_gt_regs.h
> > +++ b/drivers/gpu/drm/xe/regs/xe_gt_regs.h
> > @@ -142,6 +142,9 @@
> >  #define XEHP_SLICE_COMMON_ECO_CHICKEN1         XE_REG_MCR(0x731c, XE_REG_OPTION_MASKED)
> >  #define   MSC_MSAA_REODER_BUF_BYPASS_DISABLE   REG_BIT(14)
> >
> > +#define XE2_FLAT_CCS_BASE_RANGE_LOWER          XE_REG_MCR(0x8800)
> > +#define   XE2_FLAT_CCS_ENABLE                  REG_BIT(0)
> > +
> >  #define VF_PREEMPTION                          XE_REG(0x83a4, XE_REG_OPTION_MASKED)
> >  #define   PREEMPTION_VERTEX_COUNT              REG_GENMASK(15, 0)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> > index 8be765adf702..07a3e4cf48d1 100644
> > --- a/drivers/gpu/drm/xe/xe_device.c
> > +++ b/drivers/gpu/drm/xe/xe_device.c
> > @@ -16,6 +16,7 @@
> >  #include <drm/xe_drm.h>
> >
> >  #include "regs/xe_regs.h"
> > +#include "regs/xe_gt_regs.h"
> >  #include "xe_bo.h"
> >  #include "xe_debugfs.h"
> >  #include "xe_display.h"
> > @@ -25,6 +26,7 @@
> >  #include "xe_exec_queue.h"
> >  #include "xe_exec.h"
> >  #include "xe_gt.h"
> > +#include "xe_gt_mcr.h"
> >  #include "xe_irq.h"
> >  #include "xe_mmio.h"
> >  #include "xe_module.h"
> > @@ -342,6 +344,29 @@ static void xe_device_sanitize(struct drm_device *drm, void *arg)
> >                 xe_gt_sanitize(gt);
> >  }
> >
> > +static int xe_device_set_has_flat_ccs(struct  xe_device *xe)
> > +{
> > +       u32 reg;
> > +       int err;
> > +
> > +       if (IS_DGFX(xe) || GRAPHICS_VER(xe) < 20 || !xe->info.has_flat_ccs)
> > +               return 0;
> > +
> > +       struct xe_gt *gt = xe_root_mmio_gt(xe);
> > +
> > +       err = xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
> > +       if (err)
> > +               return err;
> > +
> > +       reg = xe_gt_mcr_unicast_read_any(gt, XE2_FLAT_CCS_BASE_RANGE_LOWER);
> > +       xe->info.has_flat_ccs = (reg & XE2_FLAT_CCS_ENABLE);
> > +
> > +       if (!xe->info.has_flat_ccs)
> > +               drm_info(&xe->drm,
> > +                        "Flat CCS has been disabled in bios, May lead to performance impact");
> > +       return 0;
> > +}
> > +
> >  int xe_device_probe(struct xe_device *xe)
> >  {
> >         struct xe_tile *tile;
> > @@ -352,6 +377,7 @@ int xe_device_probe(struct xe_device *xe)
> >         xe_pat_init_early(xe);
> >
> >         xe->info.mem_region_mask = 1;
> > +
> >         err = xe_display_init_nommio(xe);
> >         if (err)
> >                 return err;
> > @@ -390,6 +416,10 @@ int xe_device_probe(struct xe_device *xe)
> >                         goto err_irq_shutdown;
> >         }
> >
> > +       err = xe_device_set_has_flat_ccs(xe);
> > +       if (err)
> > +               return err;
> > +
> >         err = xe_mmio_probe_vram(xe);
> >         if (err)
> >                 goto err_irq_shutdown;
> > --
> > 2.25.1
> >