serial: ns16550: Handle zero <clock-frequency> value
A working device tree node of ns16550 should never be populated
with value zero for the <clock-frequency> property. Unfortunately
this is the case for the QEMU ppce500 target.
Let's try to assign plat->clock to CONFIG_SYS_NS16550_CLK as the
last resort to handle such case.
This commit should be reverted when:
- The following QEMU patch [1] is merged, and
- U-Boot CI has upgraded its QEMU version that contains the fix
[1] http://patchwork.ozlabs.org/project/qemu-devel/patch/1612362288-22216-2-git-send-email-bmeng.cn@gmail.com/
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index 1377c9a..cc121ee 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -564,6 +564,8 @@
if (!plat->clock)
plat->clock = dev_read_u32_default(dev, "clock-frequency",
CONFIG_SYS_NS16550_CLK);
+ if (!plat->clock)
+ plat->clock = CONFIG_SYS_NS16550_CLK;
if (!plat->clock) {
debug("ns16550 clock not defined\n");
return -EINVAL;