drm/mali-dp: Add writeback support for DP500.

Mali DP500 behaves differently from the rest of the Mali DP IP,
in that it does not have a one-shot mode and keeps writing the
content of the current frame to the provided memory area until
stopped. As a way of emulating the one-shot behaviour, we are
going to use the CVAL interrupt that is being raised at the
start of each frame, during prefetch phase, to act as End-of-Write
signal, but with a twist: we are going to disable the memory
write engine right after we're notified that it has been enabled,
using the knowledge that the bit controlling the enabling will
only be acted upon on the next vblank/prefetch.

CVAL interrupt will fire durint the next prefetch phase every time
the global CVAL bit gets set, so we need a state byte to track
the memory write enabling. We also need to pay attention during the
disabling of the memory write engine as that requires the CVAL bit
to be set in the control register, but we don't want to do that
during an atomic commit, as it will write into the hardware a partial
state.

Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/gpu/drm/arm/malidp_regs.h b/drivers/gpu/drm/arm/malidp_regs.h
index e2b2c496225e..93b198f3af86 100644
--- a/drivers/gpu/drm/arm/malidp_regs.h
+++ b/drivers/gpu/drm/arm/malidp_regs.h
@@ -198,7 +198,8 @@
 #define MALIDP500_DE_LG2_PTR_BASE	0x0031c
 #define MALIDP500_SE_BASE		0x00c00
 #define MALIDP500_SE_CONTROL		0x00c0c
-#define MALIDP500_SE_PTR_BASE		0x00e0c
+#define MALIDP500_SE_MEMWRITE_OUT_SIZE	0x00c2c
+#define MALIDP500_SE_MEMWRITE_BASE	0x00e00
 #define MALIDP500_DC_IRQ_BASE		0x00f00
 #define MALIDP500_CONFIG_VALID		0x00f00
 #define MALIDP500_CONFIG_ID		0x00fd4