soc: renesas: Add missing check for non-zero product register address

If the DTB for a device with an RZ/A2 SoC lacks a device node for the
BSID register, the ID validation code falls back to using a register at
address 0x0, which leads to undefined behavior (e.g. reading back a
random value).

This could be fixed by letting fam_rza2.reg point to the actual BSID
register.  However, the hardcoded fallbacks were meant for backwards
compatibility with old DTBs only, not for new SoCs.  Hence fix this by
validating renesas_family.reg before using it.

Fixes: 175f435f44b724e3 ("soc: renesas: identify RZ/A2")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20191016143306.28995-1-geert+renesas@glider.be

diff --git a/drivers/soc/renesas/renesas-soc.c b/drivers/soc/renesas/renesas-soc.c
index 45135bc..f348ae3 100644 (file)
--- a/drivers/soc/renesas/renesas-soc.c
+++ b/drivers/soc/renesas/renesas-soc.c
@@ -334,7 +334,7 @@ static int __init renesas_soc_init(void)
        if (np) {
                chipid = of_iomap(np, 0);
                of_node_put(np);
-       } else if (soc->id) {
+       } else if (soc->id && family->reg) {
                chipid = ioremap(family->reg, 4);
        }
        if (chipid) {