On Mon, May 14, 2018 at 05:20:56PM -0700, Andrey Smirnov wrote:

On Mon, May 14, 2018 at 12:14 AM, Sascha Hauer [off-list ref] wrote:

quoted

On Tue, May 08, 2018 at 02:15:02PM -0700, Andrey Smirnov wrote:

quoted

With serdev device support added there's now a corner case where:

 1. There is a DT node for a serdev device on one of the UARTs
 2. There is no driver that binds against serdev device's compatibility
    string

with 1 and 2 being true it is possible to end up in a situation where
a particualr UART has not been initalized to any baudrate when
clock_notifier_call_chain() gets called. This effectively translates
to

      set_baudrate(uart, 0);

which for LPUART driver result in a division by zero.

This probably leads to a division by zero for most drivers since
dividing by the baudrate is a common pattern. Wouldn't it be better to
catch this is console_set_baudrate()?

It would, but none of the drivers that register a callback with
clock_register_client() (serial_imx.c, serial_auart.c, stm-serial.c,
serial_lpuart.c and serial_cadence.c) use console_set_badrate() and
instead call ->setbrg() directly. Probably because
console_set_baudrate() also handles interactive baudrate switch for
f_active console devices. Serial_imx.c doesn't preform any division,
so it is safe and I can go through the rest of them to add appropriate
checks? Another option is probably to try to come up with common
clock_register_client() infrastructure(since all of the handlers are
the same) and keep that check there.

Let me know if you want me to do either.

I see. For the sake of simplicity I think we can go with your original
patch. In the auart and cadence driver the clock notify stuff is unused,
only copy paste leftover from copying the i.MX driver. That leaves the
lpuart driver which really has this problem.

Sascha

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