[Intel-gfx] [PATCH] drm/i915: flush system agent TLBs on SNB so we can WC map the PTEs

[Paulo Zanoni]

2012/10/11 Jesse Barnes <jbarnes at virtuousgeek.org>:
> I've only lightly tested this so far, but the corruption seems to be
> gone if I write the GFX_FLSH_CNTL reg after binding an object.  This
> register should control the TLB for the system agent, which is what CPU
> mapped objects will go through.
>
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
>
> diff --git a/drivers/char/agp/intel-agp.h b/drivers/char/agp/intel-agp.h
> index 6ec0fff..95f0d4d 100644
> --- a/drivers/char/agp/intel-agp.h
> +++ b/drivers/char/agp/intel-agp.h
> @@ -99,6 +99,9 @@
>  #define GFX_FLSH_CNTL          0x2170 /* 915+ */
>  #define GFX_FLSH_CNTL_VLV      0x101008
>
> +#define GFX_FLSH_CNTL          0x101008
> +#define   GFX_FLSH_CNTL_EN     (1<<0)

Notice that there's a redefinition of GFX_FLSH_CNTL with a different
value just 3 lines above. We're probably fixing gen6+ and breaking
gen5-

We write 0 to this reg in some places, but I believe that shouldn't matter.


> +
>  #define I810_DRAM_CTL          0x3000
>  #define I810_DRAM_ROW_0                0x00000001
>  #define I810_DRAM_ROW_0_SDRAM  0x00000001
> diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
> index e01f5ea..08844d6 100644
> --- a/drivers/char/agp/intel-gtt.c
> +++ b/drivers/char/agp/intel-gtt.c
> @@ -667,12 +667,8 @@ static int intel_gtt_init(void)
>         gtt_map_size = intel_private.base.gtt_total_entries * 4;
>
>         intel_private.gtt = NULL;
> -       if (INTEL_GTT_GEN < 6)
> -               intel_private.gtt = ioremap_wc(intel_private.gtt_bus_addr,
> -                                              gtt_map_size);
> -       if (intel_private.gtt == NULL)
> -               intel_private.gtt = ioremap(intel_private.gtt_bus_addr,
> -                                           gtt_map_size);
> +       intel_private.gtt = ioremap_wc(intel_private.gtt_bus_addr,
> +                                      gtt_map_size);
>         if (intel_private.gtt == NULL) {
>                 intel_private.driver->cleanup();
>                 iounmap(intel_private.registers);
> @@ -897,6 +893,7 @@ void intel_gtt_insert_sg_entries(struct sg_table *st,
>                 }
>         }
>         readl(intel_private.gtt+j-1);
> +       writel(GFX_FLSH_CNTL_EN, intel_private.registers + GFX_FLSH_CNTL);
>  }
>  EXPORT_SYMBOL(intel_gtt_insert_sg_entries);
>
> @@ -913,6 +910,7 @@ static void intel_gtt_insert_pages(unsigned int first_entry,
>                                                   j, flags);
>         }
>         readl(intel_private.gtt+j-1);
> +       writel(GFX_FLSH_CNTL_EN, intel_private.registers + GFX_FLSH_CNTL);
>  }
>
>  static int intel_fake_agp_insert_entries(struct agp_memory *mem,
> @@ -1256,7 +1254,7 @@ static int i9xx_setup(void)
>
>         reg_addr &= 0xfff80000;
>
> -       if (INTEL_GTT_GEN >= 7)
> +       if (INTEL_GTT_GEN >= 6)
>                 size = MB(2);
>
>         intel_private.registers = ioremap(reg_addr, size);
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-- 
Paulo Zanoni