[PATCH v4 11/11] drm/tyr: gem: map cached BOs for DRM_PANTHOR_BO_WB_MMAP

[Ke Sun via B4 Relay]

From: Sami Tolvanen <samitolvanen@xxxxxxxxxx>

Userspace may request a cacheable CPU mapping for a buffer it accesses
frequently. Accept DRM_PANTHOR_BO_WB_MMAP in bo_create and map the
buffer cached when the flag is set. Coherent devices already map
cached. NO_MMAP and WB_MMAP together are rejected with EINVAL.

On non-coherent platforms userspace owns the CPU cache maintenance
around GPU access to these buffers.

Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
[ Split the BO_CREATE validation and add the WB_MMAP flag checks
  from the original. - Alvin ]
Co-developed-by: Alvin Sun <alvin.sun@xxxxxxxxx>
Signed-off-by: Alvin Sun <alvin.sun@xxxxxxxxx>
---
 drivers/gpu/drm/tyr/file.rs | 25 +++++++++++++++++++------
 drivers/gpu/drm/tyr/gem.rs  | 18 +++++++++++-------
 2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/tyr/file.rs b/drivers/gpu/drm/tyr/file.rs
index d4d6a6742b2e1..6f4550d14bb39 100644
--- a/drivers/gpu/drm/tyr/file.rs
+++ b/drivers/gpu/drm/tyr/file.rs
@@ -258,19 +258,32 @@ pub(crate) fn bo_create(
         bocreate: &mut uapi::drm_panthor_bo_create,
         file: &TyrDrmFile,
     ) -> Result<u32> {
-        if bocreate.size == 0
-            || bocreate.pad != 0
-            || bocreate.flags & !uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_NO_MMAP != 0
-        {
+        if bocreate.size == 0 || bocreate.pad != 0 {
             dev_dbg!(
                 ddev.as_ref(),
-                "Invalid BO_CREATE params: size={}, pad={}, flags={:#x}\n",
+                "Invalid BO_CREATE params: size={}, pad={}\n",
                 bocreate.size,
-                bocreate.pad,
+                bocreate.pad
+            );
+            return Err(EINVAL);
+        }
+
+        let no_mmap = uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_NO_MMAP;
+        let wb_mmap = uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_WB_MMAP;
+        let valid_flags = no_mmap | wb_mmap;
+
+        if bocreate.flags & !valid_flags != 0 {
+            dev_dbg!(
+                ddev.as_ref(),
+                "Invalid BO_CREATE flags: {:#x}\n",
                 bocreate.flags
             );
             return Err(EINVAL);
         }
+        if bocreate.flags & no_mmap != 0 && bocreate.flags & wb_mmap != 0 {
+            dev_dbg!(ddev.as_ref(), "BO_CREATE: NO_MMAP conflicts with WB_MMAP\n");
+            return Err(EINVAL);
+        }
 
         if bocreate.exclusive_vm_id != 0 {
             dev_dbg!(ddev.as_ref(), "BO_CREATE: exclusive_vm_id not supported\n");
diff --git a/drivers/gpu/drm/tyr/gem.rs b/drivers/gpu/drm/tyr/gem.rs
index fad0720ce7123..d3791b62d5a7b 100644
--- a/drivers/gpu/drm/tyr/gem.rs
+++ b/drivers/gpu/drm/tyr/gem.rs
@@ -17,7 +17,8 @@
     sync::{
         aref::ARef,
         Arc, //
-    }, //
+    },
+    uapi, //
 };
 
 use crate::{
@@ -63,13 +64,16 @@ fn new(_dev: &TyrDrmDevice, _size: usize, args: BoCreateArgs) -> impl PinInit<Se
 /// Type alias for Tyr GEM buffer objects.
 pub(crate) type Bo = gem::shmem::Object<BoData>;
 
-/// Returns whether a BO should be mapped write-combine given the device's
-/// DMA coherence.
-pub(crate) fn should_map_wc(coherent: bool) -> bool {
+/// Returns whether a BO should be mapped write-combine.
+pub(crate) fn should_map_wc(coherent: bool, flags: u32) -> bool {
     if coherent {
         return false;
     }
 
+    if flags & uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_WB_MMAP != 0 {
+        return false;
+    }
+
     true
 }
 
@@ -86,7 +90,7 @@ pub(crate) fn new_object(
 
     let aligned_size = size.checked_next_multiple_of(PAGE_SIZE).ok_or(EINVAL)?;
 
-    let map_wc = should_map_wc(coherent);
+    let map_wc = should_map_wc(coherent, flags);
     let bo = Bo::new(
         ddev,
         aligned_size,
@@ -116,7 +120,7 @@ pub(crate) fn new_dummy_object(ddev: &TyrDrmDevice, coherent: bool) -> Result<AR
         ddev,
         4096,
         shmem::ObjectConfig {
-            map_wc: should_map_wc(coherent),
+            map_wc: should_map_wc(coherent, 0),
             parent_resv_obj: None,
         },
         BoCreateArgs { flags: 0 },
@@ -174,7 +178,7 @@ pub(crate) fn new(
             ddev,
             bo_size,
             shmem::ObjectConfig {
-                map_wc: should_map_wc(coherent),
+                map_wc: should_map_wc(coherent, 0),
                 parent_resv_obj: None,
             },
             BoCreateArgs { flags: 0 },

-- 
2.43.0