linux-kernel - Re: [PATCH] serial: 8250_dw: Avoid overflow in dw8250_set

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Message-ID: <CAHp75VfBCTFcO=bysUQBaN-6sYa_1LO8XSzc4WY+X0_M_SZwsQ@mail.gmail.com>
Date:   Mon, 15 Jan 2018 22:30:32 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Ed Blake <ed.blake@...drel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, nunojpg@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] serial: 8250_dw: Avoid overflow in dw8250_set_termios

On Fri, Jan 12, 2018 at 3:45 PM, Ed Blake <ed.blake@...drel.com> wrote:
> When searching for an achievable input clock rate that is within
> +/-1.6% of an integer multiple of the target baudx16 rate, there is the
> potential to overflow the i * rate calculations.
>
> For example, on a 32-bit system with a baud rate of 4000000, the
> i * max_rate calculation will overflow if i reaches 67 without finding
> an acceptable rate.
>
> Fix this by setting the upper boundary of the loop appropriately to
> avoid overflow.
>

It seems the change broke Bluetooth on some Intel platforms. I'm not
sure yet, but
see here:

https://github.com/Dunedan/mbp-2016-linux/issues/29#issuecomment-357583782

And for me the change is odd.

Why by the way neither Heikki, nor me had been Cc'ed with the change?

Perhaps I need to submit something to maintainer data base.

For now I would rather revert it and give another try.

-- 
With Best Regards,
Andy Shevchenko