Commit 204483da authored Jun 15, 2016 by Harshdeep Dhatt Committed by Carter Cooper Aug 09, 2016

msm: kgsl: Fix the ringbuffer wrap around logic



Currently, if read pointer is behind write pointer and there
is not enough space toward the end of the ringbuffer for
new commands, then write pointer is being set to 0.
This is problematic, because it leads to the overwriting of
unexecuted commands with new commands at the start of the
ringbuffer. So, instead of setting the write pointer to 0,
look for space from the start of the ringbuffer up till the
read pointer and if there is room, update the write pointer
accordingly.

CRs-Fixed: 1028465
Change-Id: I1cbdbf139b14988513a22030aa2be4a99a221880
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>

parent e94b446e

drivers/gpu/msm/adreno_ringbuffer.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -158,11 +158,18 @@ unsigned int adreno_ringbuffer_allocspace(struct adreno_ringbuffer rb,
		return RB_HOSTPTR(rb, ret);
		}

		/*
		* There isn't enough space toward the end of ringbuffer. So
		* look for space from the beginning of ringbuffer upto the
		* read pointer.
		*/
		if (dwords < rptr) {
		cmds = RB_HOSTPTR(rb, rb->_wptr);
		*cmds = cp_packet(adreno_dev, CP_NOP,
		KGSL_RB_DWORDS - rb->_wptr - 1);

		rb->_wptr = 0;
		rb->_wptr = dwords;
		return RB_HOSTPTR(rb, 0);
		}
		}

		if (rb->_wptr + dwords < rptr) {