From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756431AbZJ2Uao (ORCPT ); Thu, 29 Oct 2009 16:30:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754581AbZJ2Uan (ORCPT ); Thu, 29 Oct 2009 16:30:43 -0400 Received: from mail-pz0-f188.google.com ([209.85.222.188]:55313 "EHLO mail-pz0-f188.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754229AbZJ2Uam convert rfc822-to-8bit (ORCPT ); Thu, 29 Oct 2009 16:30:42 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=Jj4e2MIxxIRUmLEkwmB8Luzc4il/Q9Z79OP1pTiJaQ50Yn5Q2QDhcbcbQHDj5kQVsY mdeG3FVJhXOZKvgPwlQBCsk+ya8qJHiD75S1urAjrEMHZ7aMNcGzisQy8b+AK76zKhuy NpX402D0TBBCxhH3idBFto90kqEea0nuDt3e4= MIME-Version: 1.0 In-Reply-To: <1256843340.28922.14.camel@dwillia2-linux.ch.intel.com> References: <1256843340.28922.14.camel@dwillia2-linux.ch.intel.com> Date: Thu, 29 Oct 2009 13:30:47 -0700 X-Google-Sender-Auth: 06ea270473950dbd Message-ID: Subject: Fwd: [PATCH] iop13xx: workaround errata that causes uart interrupts to be missed From: Dan Williams To: alan@linux.intel.com Cc: Linux Kernel Mailing List , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ per Russell's note forwarding to Alan / LKML ] ---------- Forwarded message ---------- From: Dan Williams Date: Thu, Oct 29, 2009 at 12:09 PM Subject: [PATCH] iop13xx: workaround errata that causes uart interrupts to be missed To: linux-arm-kernel Cc: Russell King , Lennert Buytenhek Reading the uart iir register sometimes results in the interrupt being cleared without being reported.  Use the the system interrupt pending register as a fallback. This converts locations in the code that only care about the interrupt pending bit to use the iir_int_status() macro. Signed-off-by: Dan Williams --- This patch has been sitting in the 'misc' branch of the xscaleiop tree in an un-mergeable form for quite a while [1].  I finally got fed up with forward porting it and would like to try to get this workaround upstream.  There appears to be no maintainer for 8250.c, so not sure who should merge this.  I can append it to the end of my next pull request for the iop queue...? Thanks, Dan [1]: http://git.kernel.org/?p=linux/kernel/git/djbw/xscaleiop.git;a=commitdiff;h=a7d124f5  drivers/serial/8250.c |   36 +++++++++++++++++++++++++++++++++---  1 files changed, 33 insertions(+), 3 deletions(-) diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index b1ae774..c905860 100644 --- a/drivers/serial/8250.c +++ b/drivers/serial/8250.c @@ -547,6 +547,36 @@ serial_out_sync(struct uart_8250_port *up, int offset, int value)        (up->port.serial_in(&(up)->port, (offset)))  #define serial_out(up, offset, value)  \        (up->port.serial_out(&(up)->port, (offset), (value))) + +#ifndef CONFIG_ARCH_IOP13XX +#define iir_int_status(up) serial_in((up), UART_IIR) +#else +/* A silicon issue on IOP13XX causes IIR reads to return UART_IIR_NO_INT + * even if an interrupt is pending. Use the system interrupt pending + * register to check for servicing as a workaround. + */ +#include +static unsigned int iir_int_status(struct uart_8250_port *up) +{ +       unsigned long membase = (unsigned long) up->port.membase; +       unsigned long ipnd, iir; + +       ipnd = read_intpnd_1(); +       iir = UART_IIR_NO_INT; +       if (membase == IOP13XX_UART0_VIRT) { +               if (ipnd & (1 << (IRQ_IOP13XX_UART0 - 32))) +                       iir &= ~UART_IIR_NO_INT; +       } else if (membase == IOP13XX_UART1_VIRT) { +               if (ipnd & (1 << (IRQ_IOP13XX_UART1 - 32))) +                       iir &= ~UART_IIR_NO_INT; +       } else +               BUG(); +       /* clear the interupt via the LSR */ +       mem_serial_in(&up->port, UART_LSR); +       return iir; +} +#endif +  /*  * We used to support using pause I/O for certain machines.  We  * haven't supported this for a while, but just in case it's badly @@ -1572,7 +1602,7 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)                up = list_entry(l, struct uart_8250_port, list); -               iir = serial_in(up, UART_IIR); +               iir = iir_int_status(up);                if (!(iir & UART_IIR_NO_INT)) {                        serial8250_handle_port(up); @@ -1732,7 +1762,7 @@ static void serial8250_timeout(unsigned long data)        struct uart_8250_port *up = (struct uart_8250_port *)data;        unsigned int iir; -       iir = serial_in(up, UART_IIR); +       iir = iir_int_status(up);        if (!(iir & UART_IIR_NO_INT))                serial8250_handle_port(up);        mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout)); @@ -1753,7 +1783,7 @@ static void serial8250_backup_timeout(unsigned long data)                serial_out(up, UART_IER, 0);        } -       iir = serial_in(up, UART_IIR); +       iir = iir_int_status(up);        /*         * This should be a safe test for anyone who doesn't trust the