diff options
Diffstat (limited to 'drivers/staging/gma500/gtt.c')
| -rw-r--r-- | drivers/staging/gma500/gtt.c | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/drivers/staging/gma500/gtt.c b/drivers/staging/gma500/gtt.c index 461ead251bbd..a24623997e50 100644 --- a/drivers/staging/gma500/gtt.c +++ b/drivers/staging/gma500/gtt.c @@ -72,9 +72,8 @@ u32 *psb_gtt_entry(struct drm_device *dev, struct gtt_range *r) * @r: our GTT range * * Take our preallocated GTT range and insert the GEM object into - * the GTT. - * - * FIXME: gtt lock ? + * the GTT. This is protected via the gtt mutex which the caller + * must hold. */ static int psb_gtt_insert(struct drm_device *dev, struct gtt_range *r) { @@ -111,7 +110,8 @@ static int psb_gtt_insert(struct drm_device *dev, struct gtt_range *r) * @r: our GTT range * * Remove a preallocated GTT range from the GTT. Overwrite all the - * page table entries with the dummy page + * page table entries with the dummy page. This is protected via the gtt + * mutex which the caller must hold. */ static void psb_gtt_remove(struct drm_device *dev, struct gtt_range *r) @@ -136,7 +136,8 @@ static void psb_gtt_remove(struct drm_device *dev, struct gtt_range *r) * @gt: the gtt range * * Pin and build an in kernel list of the pages that back our GEM object. - * While we hold this the pages cannot be swapped out + * While we hold this the pages cannot be swapped out. This is protected + * via the gtt mutex which the caller must hold. */ static int psb_gtt_attach_pages(struct gtt_range *gt) { @@ -158,7 +159,7 @@ static int psb_gtt_attach_pages(struct gtt_range *gt) gt->npage = pages; for (i = 0; i < pages; i++) { - /* FIXME: review flags later */ + /* FIXME: needs updating as per mail from Hugh Dickins */ p = read_cache_page_gfp(mapping, i, __GFP_COLD | GFP_KERNEL); if (IS_ERR(p)) @@ -181,7 +182,8 @@ err: * * Undo the effect of psb_gtt_attach_pages. At this point the pages * must have been removed from the GTT as they could now be paged out - * and move bus address. + * and move bus address. This is protected via the gtt mutex which the + * caller must hold. */ static void psb_gtt_detach_pages(struct gtt_range *gt) { @@ -390,15 +392,18 @@ int psb_gtt_init(struct drm_device *dev, int resume) pg->gtt_phys_start = dev_priv->pge_ctl & PAGE_MASK; /* - * FIXME: video mmu has hw bug to access 0x0D0000000, - * then make gatt start at 0x0e000,0000 + * The video mmu has a hw bug when accessing 0x0D0000000. + * Make gatt start at 0x0e000,0000. This doesn't actually + * matter for us but may do if the video acceleration ever + * gets opened up. */ pg->mmu_gatt_start = 0xE0000000; pg->gtt_start = pci_resource_start(dev->pdev, PSB_GTT_RESOURCE); gtt_pages = pci_resource_len(dev->pdev, PSB_GTT_RESOURCE) >> PAGE_SHIFT; - /* CDV workaround */ + /* Some CDV firmware doesn't report this currently. In which case the + system has 64 gtt pages */ if (pg->gtt_start == 0 || gtt_pages == 0) { dev_err(dev->dev, "GTT PCI BAR not initialized.\n"); gtt_pages = 64; @@ -412,13 +417,16 @@ int psb_gtt_init(struct drm_device *dev, int resume) if (pg->gatt_pages == 0 || pg->gatt_start == 0) { static struct resource fudge; /* Preferably peppermint */ - /* This can occur on CDV SDV systems. Fudge it in this case. We really don't care what imaginary space is being allocated at this point */ dev_err(dev->dev, "GATT PCI BAR not initialized.\n"); pg->gatt_start = 0x40000000; pg->gatt_pages = (128 * 1024 * 1024) >> PAGE_SHIFT; + /* This is a little confusing but in fact the GTT is providing + a view from the GPU into memory and not vice versa. As such + this is really allocating space that is not the same as the + CPU address space on CDV */ fudge.start = 0x40000000; fudge.end = 0x40000000 + 128 * 1024 * 1024 - 1; fudge.name = "fudge"; |