misc: fastrpc: make sure memory read and writes are visible

[ Upstream commit 415a0729 ]

dma_alloc_coherent buffers could have writes queued in store buffers so
commit them before sending buffer to DSP using correct dma barriers.
Same with vice-versa.

Fixes: c68cfb71 ("misc: fastrpc: Add support for context Invoke method")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/misc/fastrpc.c

@@ -790,6 +790,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 		if (err)
 			goto bail;
 	}
+
+	/* make sure that all CPU memory writes are seen by DSP */
+	dma_wmb();
 	/* Send invoke buffer to remote dsp */
 	err = fastrpc_invoke_send(fl->sctx, ctx, kernel, handle);
 	if (err)
@@ -806,6 +809,8 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 		goto bail;
 
 	if (ctx->nscalars) {
+		/* make sure that all memory writes by DSP are seen by CPU */
+		dma_rmb();
 		/* populate all the output buffers with results */
 		err = fastrpc_put_args(ctx, kernel);
 		if (err)