From: Serge Semin <Sergey.Semin@baikalelectronics.ru> To: Daniel Winkler <danielwinkler@google.com> Cc: 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>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 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 01:37:13 +0300 [thread overview] Message-ID: <20200701223713.gavale4aramu3xnb@mobilestation> (raw) In-Reply-To: <20200701211337.3027448-1-danielwinkler@google.com> 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. -Sergey > > The driver is in the cros tree at drivers/bluetooth/hci_qca.c > and uses the serdev interface. Specifically, this is the > QCA_ROME chipset. > > > Daniel Winkler (1): > Revert "serial: 8250: Fix max baud limit in generic 8250 port" > > drivers/tty/serial/8250/8250_port.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > -- > 2.27.0.212.ge8ba1cc988-goog >
WARNING: multiple messages have this Message-ID (diff)
From: Serge Semin <Sergey.Semin@baikalelectronics.ru> To: Daniel Winkler <danielwinkler@google.com> Cc: chromeos-bluetooth-upstreaming <chromeos-bluetooth-upstreaming@chromium.org>, Vignesh Raghavendra <vigneshr@ti.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 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, Jiri Slaby <jslaby@suse.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 01:37:13 +0300 [thread overview] Message-ID: <20200701223713.gavale4aramu3xnb@mobilestation> (raw) In-Reply-To: <20200701211337.3027448-1-danielwinkler@google.com> 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. -Sergey > > The driver is in the cros tree at drivers/bluetooth/hci_qca.c > and uses the serdev interface. Specifically, this is the > QCA_ROME chipset. > > > Daniel Winkler (1): > Revert "serial: 8250: Fix max baud limit in generic 8250 port" > > drivers/tty/serial/8250/8250_port.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > -- > 2.27.0.212.ge8ba1cc988-goog > _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek
next prev parent reply other threads:[~2020-07-01 22:37 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 ` Serge Semin [this message] 2020-07-01 22:37 ` [PATCH v2 0/1] " 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 2020-07-02 7:37 ` Greg Kroah-Hartman
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