diff options
Diffstat (limited to 'shared-core/mach64_drv.h')
| -rw-r--r-- | shared-core/mach64_drv.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/shared-core/mach64_drv.h b/shared-core/mach64_drv.h index 7bd40a68..1768a2a4 100644 --- a/shared-core/mach64_drv.h +++ b/shared-core/mach64_drv.h @@ -527,6 +527,9 @@ extern void mach64_driver_irq_uninstall(struct drm_device * dev); /* ================================================================ * Ring operations + * + * Since the Mach64 bus master engine requires polling, these functions end + * up being called frequently, hence being inline. */ static __inline__ void mach64_ring_start(drm_mach64_private_t * dev_priv) @@ -591,6 +594,18 @@ static __inline__ void mach64_ring_resume(drm_mach64_private_t * dev_priv, } } +/** + * Poll the ring head and make sure the bus master is alive. + * + * Mach64's bus master engine will stop if there are no more entries to process. + * This function polls the engine for the last processed entry and calls + * mach64_ring_resume if there is an unprocessed entry. + * + * Note also that, since we update the ring tail while the bus master engine is + * in operation, it is possible that the last tail update was too late to be + * processed, and the bus master engine stops at the previous tail position. + * Therefore it is important to call this function frequently. + */ static __inline__ void mach64_ring_tick(drm_mach64_private_t * dev_priv, drm_mach64_descriptor_ring_t * ring) { @@ -676,6 +691,11 @@ mach64_update_ring_snapshot(drm_mach64_private_t * dev_priv) /* ================================================================ * DMA macros + * + * Mach64's ring buffer doesn't take register writes directly. These + * have to be written indirectly in DMA buffers. These macros simplify + * the task of setting up a buffer, writing commands to it, and + * queuing the buffer in the ring. */ #define DMALOCALS \ |