Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759428AbaJ3La6 (ORCPT ); Thu, 30 Oct 2014 07:30:58 -0400 Received: from mail-wi0-f180.google.com ([209.85.212.180]:44024 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759280AbaJ3Lay (ORCPT ); Thu, 30 Oct 2014 07:30:54 -0400 Message-ID: <54522163.8030408@linaro.org> Date: Thu, 30 Oct 2014 11:30:43 +0000 From: Daniel Thompson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Stephen Boyd , Greg Kroah-Hartman CC: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-serial@vger.kernel.org, Frank Rowand Subject: Re: [PATCH 2/2] tty: serial: msm: Support sysrq on uartDM devices References: <1414606478-13709-1-git-send-email-sboyd@codeaurora.org> <1414606478-13709-3-git-send-email-sboyd@codeaurora.org> In-Reply-To: <1414606478-13709-3-git-send-email-sboyd@codeaurora.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/10/14 18:14, Stephen Boyd wrote: > To properly support sysrq on uartDM hardware we need to properly > handle break characters. With the DM hardware the fifo can pack 4 > characters at a time, where a break is indicated by an all zero > byte. Unfortunately, we can't differentiate between an all zero > byte for a break and an all zero byte of data, so try and do as > best we can. First unmask the RX break start interrupt and record > the interrupt when it arrives. Then while processing the fifo, > detect the break by searching for an all zero character as long > as we recently received an RX break start interrupt. This should > make sysrq work fairly well. > > Cc: Frank Rowand > Cc: Daniel Thompson > Signed-off-by: Stephen Boyd > --- > drivers/tty/serial/msm_serial.c | 41 +++++++++++++++++++++++++++++++---------- > drivers/tty/serial/msm_serial.h | 2 ++ > 2 files changed, 33 insertions(+), 10 deletions(-) > > diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c > index cedcc36762a2..d44c04976f7a 100644 > --- a/drivers/tty/serial/msm_serial.c > +++ b/drivers/tty/serial/msm_serial.c > @@ -54,6 +54,7 @@ struct msm_port { > unsigned int imr; > int is_uartdm; > unsigned int old_snap_state; > + bool break_detected; > }; > > static inline void wait_for_xmitr(struct uart_port *port) > @@ -126,23 +127,38 @@ static void handle_rx_dm(struct uart_port *port, unsigned int misr) > > while (count > 0) { > unsigned char buf[4]; > + int sysrq, r_count, i; > > sr = msm_read(port, UART_SR); > if ((sr & UART_SR_RX_READY) == 0) { > msm_port->old_snap_state -= count; > break; > } > + > ioread32_rep(port->membase + UARTDM_RF, buf, 1); > - if (sr & UART_SR_RX_BREAK) { > - port->icount.brk++; > - if (uart_handle_break(port)) > - continue; > - } else if (sr & UART_SR_PAR_FRAME_ERR) > - port->icount.frame++; > + r_count = min_t(int, count, sizeof(buf)); > + > + for (i = 0; i < r_count; i++) { > + char flag = TTY_NORMAL; > > - /* TODO: handle sysrq */ > - tty_insert_flip_string(tport, buf, min(count, 4)); > - count -= 4; > + if (msm_port->break_detected && buf[i] == 0) { > + port->icount.brk++; > + flag = TTY_BREAK; > + msm_port->break_detected = false; > + if (uart_handle_break(port)) > + continue; > + } > + > + if (!(port->read_status_mask & UART_SR_RX_BREAK)) > + flag = TTY_NORMAL; flag is already known to be TTY_NORMAL. > + > + spin_unlock(&port->lock); Is it safe to unlock at this point? count may no longer be valid when we return. > + sysrq = uart_handle_sysrq_char(port, buf[i]); > + spin_lock(&port->lock); > + if (!sysrq) > + tty_insert_flip_char(tport, buf[i], flag); flag has a constant value here. > + } > + count -= r_count; > } > > spin_unlock(&port->lock); > @@ -291,6 +307,11 @@ static irqreturn_t msm_irq(int irq, void *dev_id) > misr = msm_read(port, UART_MISR); > msm_write(port, 0, UART_IMR); /* disable interrupt */ > > + if (misr & UART_IMR_RXBREAK_START) { > + msm_port->break_detected = true; > + msm_write(port, UART_CR_CMD_RESET_RXBREAK_START, UART_CR); > + } > + > if (misr & (UART_IMR_RXLEV | UART_IMR_RXSTALE)) { > if (msm_port->is_uartdm) > handle_rx_dm(port, misr); > @@ -496,7 +517,7 @@ static int msm_startup(struct uart_port *port) > > /* turn on RX and CTS interrupts */ > msm_port->imr = UART_IMR_RXLEV | UART_IMR_RXSTALE | > - UART_IMR_CURRENT_CTS; > + UART_IMR_CURRENT_CTS | UART_IMR_RXBREAK_START; > > if (msm_port->is_uartdm) { > msm_write(port, 0xFFFFFF, UARTDM_DMRX); > diff --git a/drivers/tty/serial/msm_serial.h b/drivers/tty/serial/msm_serial.h > index 73d3abe71e79..3e1c7138d8cd 100644 > --- a/drivers/tty/serial/msm_serial.h > +++ b/drivers/tty/serial/msm_serial.h > @@ -65,6 +65,7 @@ > #define UART_CR_TX_ENABLE (1 << 2) > #define UART_CR_RX_DISABLE (1 << 1) > #define UART_CR_RX_ENABLE (1 << 0) > +#define UART_CR_CMD_RESET_RXBREAK_START ((1 << 11) | (2 << 4)) > > #define UART_IMR 0x0014 > #define UART_IMR_TXLEV (1 << 0) > @@ -72,6 +73,7 @@ > #define UART_IMR_RXLEV (1 << 4) > #define UART_IMR_DELTA_CTS (1 << 5) > #define UART_IMR_CURRENT_CTS (1 << 6) > +#define UART_IMR_RXBREAK_START (1 << 10) > > #define UART_IPR_RXSTALE_LAST 0x20 > #define UART_IPR_STALE_LSB 0x1F > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/