remoteproc: stm32: Parse syscon that will manage M4 synchronisation

Get from the DT the syncon to probe the state of the remote processor
and the location of the resource table.

Mainly based on the work published by Arnaud Pouliquen [1].

[1]. https://patchwork.kernel.org/project/linux-remoteproc/list/?series=239877Acked-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Loic Pallardy <loic.pallardy@st.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20200714200445.1427257-6-mathieu.poirier@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/stm32_rproc.c

@@ -71,6 +71,8 @@ struct stm32_rproc {
 	struct reset_control *rst;
 	struct stm32_syscon hold_boot;
 	struct stm32_syscon pdds;
+	struct stm32_syscon m4_state;
+	struct stm32_syscon rsctbl;
 	int wdg_irq;
 	u32 nb_rmems;
 	struct stm32_rproc_mem *rmems;
@@ -607,6 +609,30 @@ static int stm32_rproc_parse_dt(struct platform_device *pdev,
 
 	*auto_boot = of_property_read_bool(np, "st,auto-boot");
 
+	/*
+	 * See if we can check the M4 status, i.e if it was started
+	 * from the boot loader or not.
+	 */
+	err = stm32_rproc_get_syscon(np, "st,syscfg-m4-state",
+				     &ddata->m4_state);
+	if (err) {
+		/* remember this */
+		ddata->m4_state.map = NULL;
+		/* no coprocessor state syscon (optional) */
+		dev_warn(dev, "m4 state not supported\n");
+
+		/* no need to go further */
+		return 0;
+	}
+
+	/* See if we can get the resource table */
+	err = stm32_rproc_get_syscon(np, "st,syscfg-rsc-tbl",
+				     &ddata->rsctbl);
+	if (err) {
+		/* no rsc table syscon (optional) */
+		dev_warn(dev, "rsc tbl syscon not supported\n");
+	}
+
 	return 0;
 }