On Tue, Feb 22, 2022 at 08:22:01PM +0530, Balasubramani Vivekanandan wrote:
Fast copy using non-temporal instructions for x86 currently exists at two
locations. One is implemented in i915 driver at i915/i915_memcpy.c and
another copy at drm_cache.c. The plan is to remove the duplicate
implementation in i915 driver and use the functions from drm_cache.c.
A variant of drm_memcpy_from_wc() is added in drm_cache.c which accepts
address as argument instead of iosys_map for destination. It is a very
common scenario in i915 to copy from a WC memory type, which may be an
io memory or a system memory to a destination address pointing to system
memory. To avoid the overhead of creating iosys_map type for the
destination, new variant is created to accept the address directly.
Also a new function is exported in drm_cache.c to find if the fast copy
is supported by the platform or not. It is required for i915.
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Thomas Hellstr_m <thomas.hellstrom@xxxxxxxxxxxxxxx>
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@xxxxxxxxx>
---
drivers/gpu/drm/drm_cache.c | 54 +++++++++++++++++++++++++++++++++++++
include/drm/drm_cache.h | 3 +++
2 files changed, 57 insertions(+)
diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
index a21c1350eb09..eb0bcd33665e 100644
--- a/drivers/gpu/drm/drm_cache.c
+++ b/drivers/gpu/drm/drm_cache.c
@@ -358,6 +358,54 @@ void drm_memcpy_from_wc(struct iosys_map *dst,
}
EXPORT_SYMBOL(drm_memcpy_from_wc);
+/**
+ * drm_memcpy_from_wc_vaddr - Perform the fastest available memcpy from a source
+ * that may be WC.
.... to a destination in system memory.
+ * @dst: The destination pointer
+ * @src: The source pointer
+ * @len: The size of the area to transfer in bytes
+ *
+ * Same as drm_memcpy_from_wc except destination is accepted as system memory
+ * address. Useful in situations where passing destination address as iosys_map
+ * is simply an overhead and can be avoided.
although one could do drm_memcpy_from_wc(IOSYS_MAP_INIT_VADDR(addr), ...
(if IOSYS_MAP_INIT_VADDR provided a cast to the struct).
+ */
+void drm_memcpy_from_wc_vaddr(void *dst, const struct iosys_map *src,
name here is confusing as we are copying *to* system memory. Maybe
drm_memcpy_vaddr_from_wc()? Not sure it's better. Maybe someone in Cc
has a better suggestion
( To be honest, this whole _from_wc() suffix sound weird when are checking I/O
vs system memory.... it may have been the motivation, but maybe it
shouldn't be the name of the memcpy() variant )
The implementation looks ok and follows drm_memcpy_from_wc()
Lucas De Marchi
+ unsigned long len)
+{
+ if (WARN_ON(in_interrupt())) {
+ iosys_map_memcpy_from(dst, src, 0, len);
+ return;
+ }
+
+ if (static_branch_likely(&has_movntdqa)) {
+ __drm_memcpy_from_wc(dst,
+ src->is_iomem ?
+ (void const __force *)src->vaddr_iomem :
+ src->vaddr,
+ len);
+ return;
+ }
+
+ iosys_map_memcpy_from(dst, src, 0, len);
+}
+EXPORT_SYMBOL(drm_memcpy_from_wc_vaddr);
+
+/*
+ * drm_memcpy_fastcopy_supported - Returns if fast copy using non-temporal
+ * instructions is supported
+ *
+ * Returns true if platform has support for fast copying from wc memory type
+ * using non-temporal instructions. Else false.
+ */
+bool drm_memcpy_fastcopy_supported(void)
+{
+ if (static_branch_likely(&has_movntdqa))
+ return true;
+
+ return false;
+}
+EXPORT_SYMBOL(drm_memcpy_fastcopy_supported);
+
/*
* drm_memcpy_init_early - One time initialization of the WC memcpy code
*/
@@ -382,6 +430,12 @@ void drm_memcpy_from_wc(struct iosys_map *dst,
}
EXPORT_SYMBOL(drm_memcpy_from_wc);
+bool drm_memcpy_fastcopy_supported(void)
+{
+ return false;
+}
+EXPORT_SYMBOL(drm_memcpy_fastcopy_supported);
+
void drm_memcpy_init_early(void)
{
}
diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h
index 22deb216b59c..8f48e4dcd7dc 100644
--- a/include/drm/drm_cache.h
+++ b/include/drm/drm_cache.h
@@ -77,4 +77,7 @@ void drm_memcpy_init_early(void);
void drm_memcpy_from_wc(struct iosys_map *dst,
const struct iosys_map *src,
unsigned long len);
+bool drm_memcpy_fastcopy_supported(void);
+void drm_memcpy_from_wc_vaddr(void *dst, const struct iosys_map *src,
+ unsigned long len);
#endif
--
2.25.1
