remoteproc/omap: Add a sanity check for DSP boot address alignment

The DSP remote processors on OMAP SoCs require a boot register to
be programmed with a boot address, and this boot address needs to
be on a 1KB boundary. The current code is simply masking the boot
address appropriately without performing any sanity checks before
releasing the resets. An unaligned boot address results in an
undefined execution behavior and can result in various bus errors
like MMU Faults or L3 NoC errors. Such errors are hard to debug and
can be easily avoided by adding a sanity check for the alignment
before booting a DSP remote processor.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200324110035.29907-4-t-kristo@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/omap_remoteproc.c

@@ -121,14 +121,23 @@ static void omap_rproc_kick(struct rproc *rproc, int vqid)
  * @rproc: handle of a remote processor
  *
  * Set boot address for a supported DSP remote processor.
+ *
+ * Return: 0 on success, or -EINVAL if boot address is not aligned properly
  */
-static void omap_rproc_write_dsp_boot_addr(struct rproc *rproc)
+static int omap_rproc_write_dsp_boot_addr(struct rproc *rproc)
 {
+	struct device *dev = rproc->dev.parent;
 	struct omap_rproc *oproc = rproc->priv;
 	struct omap_rproc_boot_data *bdata = oproc->boot_data;
 	u32 offset = bdata->boot_reg;
 
-	regmap_write(bdata->syscon, offset, rproc->bootaddr);
+	if (rproc->bootaddr & (SZ_1K - 1)) {
+		dev_err(dev, "invalid boot address 0x%llx, must be aligned on a 1KB boundary\n",
+			rproc->bootaddr);
+		return -EINVAL;
+	}
+
+	return regmap_write(bdata->syscon, offset, rproc->bootaddr);
 }
 
 /*
@@ -145,8 +154,11 @@ static int omap_rproc_start(struct rproc *rproc)
 	int ret;
 	struct mbox_client *client = &oproc->client;
 
-	if (oproc->boot_data)
-		omap_rproc_write_dsp_boot_addr(rproc);
+	if (oproc->boot_data) {
+		ret = omap_rproc_write_dsp_boot_addr(rproc);
+		if (ret)
+			return ret;
+	}
 
 	client->dev = dev;
 	client->tx_done = NULL;