From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Daniel Winkler <danielwinkler@google.com>,
Serge Semin <fancer.lancer@gmail.com>,
linux-serial@vger.kernel.org, linux-mediatek@lists.infradead.org,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
BlueZ <linux-bluetooth@vger.kernel.org>,
chromeos-bluetooth-upstreaming
<chromeos-bluetooth-upstreaming@chromium.org>,
stable@vger.kernel.org, abhishekpandit@chromium.org,
Aaron Sierra <asierra@xes-inc.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Jiri Slaby <jslaby@suse.com>, Lukas Wunner <lukas@wunner.de>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/1] Revert "serial: 8250: Fix max baud limit in generic 8250 port"
Date: Thu, 2 Jul 2020 09:37:20 +0200 [thread overview]
Message-ID: <20200702073720.GE1073011@kroah.com> (raw)
In-Reply-To: <20200701223713.gavale4aramu3xnb@mobilestation>
On Thu, Jul 02, 2020 at 01:37:13AM +0300, Serge Semin wrote:
> On Wed, Jul 01, 2020 at 02:13:36PM -0700, Daniel Winkler wrote:
> >
> > This change regresses the QCA6174A-3 bluetooth chip, preventing
> > firmware from being properly loaded. Without this change, the
> > chip works as intended.
> >
> > The device is the Kukui Chromebook using the Mediatek chipset
> > and the 8250_mtk uart. Initial controller baudrate is 115200
> > and operating speed is 3000000. Our entire suite of bluetooth
> > tests now fail on this platform due to an apparent failure to
> > sync its firmware on initialization.
>
> Ok. It's mediatek 8250 driver, which is responsible for the failure.
> Then we'll have two options:
>
> 1) Add a new capability like UART_CAP_NO16DIV and take it into account
> in the serial8250_get_baud_rate() method.
>
> I don't have a documentation for the Mediatek UART port, but it seems to me
> that that controller calculates the baud rate differently from the standard
> 8250 port. A standard 8250 port does that by the next formulae:
> baud = uartclk / (16 * divisor).
> While it seems to me that the Mediatek port uses the formulae like:
> baud = uartclk / divisor. (Please, correct me if I'm wrong)
> If so, then we could introduce a new capability like UART_CAP_NO16DIV. The
> 8250_mtk driver will add it to the 8250-port capabilities field. The
> serial8250_get_baud_rate() method should be altered in a way so one would check
> whether the UART_CAP_NO16DIV flag is set and if it is then the
> uart_get_baud_rate() function will be called without uartclk normalized by the
> factor of 16.
>
> 2) Manually call serial8250_do_set_divisor() in the custom set_termios()
> callback.
>
> Just add the uart_update_timeout() and serial8250_do_set_divisor() methods
> invocation into the mtk8250_set_termios() function, which the original commit
> 81bb549fdf14 ("serial: 8250_mtk: support big baud rate") author should have
> done in the first place.
Sounds like a sane fix, thanks for looking into this.
greg k-h
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: chromeos-bluetooth-upstreaming
<chromeos-bluetooth-upstreaming@chromium.org>,
Vignesh Raghavendra <vigneshr@ti.com>,
Jiri Slaby <jslaby@suse.com>,
linux-kernel@vger.kernel.org,
Serge Semin <fancer.lancer@gmail.com>,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
BlueZ <linux-bluetooth@vger.kernel.org>,
Lukas Wunner <lukas@wunner.de>,
linux-mediatek@lists.infradead.org, stable@vger.kernel.org,
linux-serial@vger.kernel.org,
Daniel Winkler <danielwinkler@google.com>,
abhishekpandit@chromium.org, Aaron Sierra <asierra@xes-inc.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH v2 0/1] Revert "serial: 8250: Fix max baud limit in generic 8250 port"
Date: Thu, 2 Jul 2020 09:37:20 +0200 [thread overview]
Message-ID: <20200702073720.GE1073011@kroah.com> (raw)
In-Reply-To: <20200701223713.gavale4aramu3xnb@mobilestation>
On Thu, Jul 02, 2020 at 01:37:13AM +0300, Serge Semin wrote:
> On Wed, Jul 01, 2020 at 02:13:36PM -0700, Daniel Winkler wrote:
> >
> > This change regresses the QCA6174A-3 bluetooth chip, preventing
> > firmware from being properly loaded. Without this change, the
> > chip works as intended.
> >
> > The device is the Kukui Chromebook using the Mediatek chipset
> > and the 8250_mtk uart. Initial controller baudrate is 115200
> > and operating speed is 3000000. Our entire suite of bluetooth
> > tests now fail on this platform due to an apparent failure to
> > sync its firmware on initialization.
>
> Ok. It's mediatek 8250 driver, which is responsible for the failure.
> Then we'll have two options:
>
> 1) Add a new capability like UART_CAP_NO16DIV and take it into account
> in the serial8250_get_baud_rate() method.
>
> I don't have a documentation for the Mediatek UART port, but it seems to me
> that that controller calculates the baud rate differently from the standard
> 8250 port. A standard 8250 port does that by the next formulae:
> baud = uartclk / (16 * divisor).
> While it seems to me that the Mediatek port uses the formulae like:
> baud = uartclk / divisor. (Please, correct me if I'm wrong)
> If so, then we could introduce a new capability like UART_CAP_NO16DIV. The
> 8250_mtk driver will add it to the 8250-port capabilities field. The
> serial8250_get_baud_rate() method should be altered in a way so one would check
> whether the UART_CAP_NO16DIV flag is set and if it is then the
> uart_get_baud_rate() function will be called without uartclk normalized by the
> factor of 16.
>
> 2) Manually call serial8250_do_set_divisor() in the custom set_termios()
> callback.
>
> Just add the uart_update_timeout() and serial8250_do_set_divisor() methods
> invocation into the mtk8250_set_termios() function, which the original commit
> 81bb549fdf14 ("serial: 8250_mtk: support big baud rate") author should have
> done in the first place.
Sounds like a sane fix, thanks for looking into this.
greg k-h
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Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
next prev parent reply other threads:[~2020-07-02 7:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 21:13 [PATCH v2 0/1] Revert "serial: 8250: Fix max baud limit in generic 8250 port" Daniel Winkler
2020-07-01 21:13 ` Daniel Winkler
2020-07-01 21:13 ` [PATCH v2 1/1] " Daniel Winkler
2020-07-01 21:13 ` Daniel Winkler
2020-07-02 7:36 ` Greg Kroah-Hartman
2020-07-02 7:36 ` Greg Kroah-Hartman
2020-07-01 22:37 ` [PATCH v2 0/1] " Serge Semin
2020-07-01 22:37 ` Serge Semin
2020-07-02 4:11 ` Lukas Wunner
2020-07-02 8:46 ` Andy Shevchenko
2020-07-02 8:46 ` Andy Shevchenko
2020-07-02 7:37 ` Greg Kroah-Hartman [this message]
2020-07-02 7:37 ` Greg Kroah-Hartman
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