From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory CLEMENT Subject: Re: [PATCH 08/16] serial: mvebu-uart: clear state register before IRQ request Date: Fri, 06 Oct 2017 14:40:47 +0200 Message-ID: <878tgofnzk.fsf@free-electrons.com> References: <20171006101344.15590-1-miquel.raynal@free-electrons.com> <20171006101344.15590-9-miquel.raynal@free-electrons.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20171006101344.15590-9-miquel.raynal-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> (Miquel Raynal's message of "Fri, 6 Oct 2017 12:13:36 +0200") Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Miquel Raynal Cc: Greg Kroah-Hartman , Linus Walleij , Jason Cooper , Andrew Lunn , Sebastian Hesselbarth , Jiri Slaby , Catalin Marinas , Will Deacon , Thomas Petazzoni , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Allen Yan , Antoine Tenart , Nadav Haklai , linux-gpio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Wilson Ding , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-gpio@vger.kernel.org Hi Miquel, On ven., oct. 06 2017, Miquel Raynal wrote: > From: Allen Yan > > When receiving data on RX pin before ->uart_startup() is called, some > error bits in the state register could be set up (like BRK_DET). > > This is harmless when using only the standard UART (error bits are > read-only), but may procude an endless loop once in the extended UART produce > RX interrupt handler (error bits must be cleared). > > Clear the status register in ->uart_startup() to avoid this situation. > > Signed-off-by: Allen Yan > Signed-off-by: Miquel Raynal Reviewed-by: Gregory CLEMENT Thanks, Gregory > --- > drivers/tty/serial/mvebu-uart.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c > index 81a3d2714fd3..67f302748b78 100644 > --- a/drivers/tty/serial/mvebu-uart.c > +++ b/drivers/tty/serial/mvebu-uart.c > @@ -322,6 +322,12 @@ static int mvebu_uart_startup(struct uart_port *port) > writel(CTRL_TXFIFO_RST | CTRL_RXFIFO_RST, > port->membase + UART_CTRL(port)); > udelay(1); > + > + /* Clear the error bits of state register before IRQ request */ > + ret = readl(port->membase + UART_STAT); > + ret |= STAT_BRK_ERR; > + writel(ret, port->membase + UART_STAT); > + > writel(CTRL_BRK_INT, port->membase + UART_CTRL(port)); > > ctl = readl(port->membase + UART_INTR(port)); > -- > 2.11.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregory.clement@free-electrons.com (Gregory CLEMENT) Date: Fri, 06 Oct 2017 14:40:47 +0200 Subject: [PATCH 08/16] serial: mvebu-uart: clear state register before IRQ request In-Reply-To: <20171006101344.15590-9-miquel.raynal@free-electrons.com> (Miquel Raynal's message of "Fri, 6 Oct 2017 12:13:36 +0200") References: <20171006101344.15590-1-miquel.raynal@free-electrons.com> <20171006101344.15590-9-miquel.raynal@free-electrons.com> Message-ID: <878tgofnzk.fsf@free-electrons.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Miquel, On ven., oct. 06 2017, Miquel Raynal wrote: > From: Allen Yan > > When receiving data on RX pin before ->uart_startup() is called, some > error bits in the state register could be set up (like BRK_DET). > > This is harmless when using only the standard UART (error bits are > read-only), but may procude an endless loop once in the extended UART produce > RX interrupt handler (error bits must be cleared). > > Clear the status register in ->uart_startup() to avoid this situation. > > Signed-off-by: Allen Yan > Signed-off-by: Miquel Raynal Reviewed-by: Gregory CLEMENT Thanks, Gregory > --- > drivers/tty/serial/mvebu-uart.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c > index 81a3d2714fd3..67f302748b78 100644 > --- a/drivers/tty/serial/mvebu-uart.c > +++ b/drivers/tty/serial/mvebu-uart.c > @@ -322,6 +322,12 @@ static int mvebu_uart_startup(struct uart_port *port) > writel(CTRL_TXFIFO_RST | CTRL_RXFIFO_RST, > port->membase + UART_CTRL(port)); > udelay(1); > + > + /* Clear the error bits of state register before IRQ request */ > + ret = readl(port->membase + UART_STAT); > + ret |= STAT_BRK_ERR; > + writel(ret, port->membase + UART_STAT); > + > writel(CTRL_BRK_INT, port->membase + UART_CTRL(port)); > > ctl = readl(port->membase + UART_INTR(port)); > -- > 2.11.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com