From: hector.palacios@digi•com (Hector Palacios)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 3/3] serial: mxs-auart: move irq handling to a tasklet
Date: Fri, 29 Nov 2013 19:04:49 +0100 [thread overview]
Message-ID: <5298D741.1080100@digi.com> (raw)
In-Reply-To: <201311291800.12366.marex@denx.de>
On 11/29/2013 06:00 PM, Marek Vasut wrote:
> Dear Hector Palacios,
>
>> The ISR was handling CTS flag and RX/TX processing.
>> Occasionally interrupts were coming in the middle of the ISR and
>> led to blocking transmission (with hw flow) or loss of data.
>> This patch moves this processing to a tasklet that the ISR schedules.
>>
>> Signed-off-by: Hector Palacios <hector.palacios@digi•com>
>> ---
>> drivers/tty/serial/mxs-auart.c | 61
>> +++++++++++++++++++++++++++--------------- 1 file changed, 39
>> insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/tty/serial/mxs-auart.c
>> b/drivers/tty/serial/mxs-auart.c index e5540c89dd48..7021269c70b2 100644
>> --- a/drivers/tty/serial/mxs-auart.c
>> +++ b/drivers/tty/serial/mxs-auart.c
>> @@ -148,6 +148,10 @@ struct mxs_auart_port {
>> struct clk *clk;
>> struct device *dev;
>>
>> + struct tasklet_struct tasklet;
>> + unsigned int irq_status;
>> + unsigned int status;
>> +
>> /* for DMA */
>> struct scatterlist tx_sgl;
>> struct dma_chan *tx_dma_chan;
>> @@ -680,38 +684,48 @@ static void mxs_auart_settermios(struct uart_port *u,
>> }
>> }
>>
>> +/*
>> + * tasklet handling tty stuff outside the interrupt handler.
>> + */
>> +static void mxs_auart_tasklet_func(unsigned long data)
>> +{
>> + struct uart_port *port = (struct uart_port *)data;
>> + struct mxs_auart_port *s = to_auart_port(port);
>> +
>> + /* Handle status irq */
>> + if (s->irq_status & AUART_INTR_CTSMIS) {
>> + uart_handle_cts_change(&s->port, s->status & AUART_STAT_CTS);
>> + writel(AUART_INTR_CTSMIS,
>> + s->port.membase + AUART_INTR_CLR);
>> + }
>> + /* Handle receive irq */
>> + if (s->irq_status & (AUART_INTR_RTIS | AUART_INTR_RXIS)) {
>> + if (!auart_dma_enabled(s))
>> + mxs_auart_rx_chars(s);
>> + }
>> + /* Handle transmit irq */
>> + if (s->irq_status & AUART_INTR_TXIS)
>> + mxs_auart_tx_chars(s);
>> +}
>> +
>> static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
>> {
>> - u32 istat;
>> struct mxs_auart_port *s = context;
>> - u32 stat = readl(s->port.membase + AUART_STAT);
>>
>> - istat = readl(s->port.membase + AUART_INTR);
>> + s->status = readl(s->port.membase + AUART_STAT);
>> + s->irq_status = readl(s->port.membase + AUART_INTR);
>
> Aren't you up for a nice race condition here if you get interrupt while checking
> the s->irq_status bits in the tasklet ?
Sad, but true. :-(
But if I need to wait on the ISR for the tasklet to process then this patch loses its
original meaning. Argh... it works so nicely!
Best regards,
--
Hector Palacios
next prev parent reply other threads:[~2013-11-29 18:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-29 16:35 [PATCH 0/3] serial: mxs-auart: flush_buffer hook and interrupt processing Hector Palacios
2013-11-29 16:35 ` [PATCH 1/3] serial: mxs-auart: implement flush_buffer hook Hector Palacios
2013-11-29 16:50 ` Marek Vasut
2013-11-29 17:49 ` Hector Palacios
2013-11-29 18:02 ` Marek Vasut
2013-11-29 18:02 ` Lucas Stach
2013-11-29 16:35 ` [PATCH 2/3] serial: mxs-auart: check BUSY flag on tx_empty hook Hector Palacios
2013-11-29 16:35 ` [PATCH 3/3] serial: mxs-auart: move irq handling to a tasklet Hector Palacios
2013-11-29 17:00 ` Marek Vasut
2013-11-29 18:04 ` Hector Palacios [this message]
2013-11-29 16:44 ` [PATCH 0/3] serial: mxs-auart: flush_buffer hook and interrupt processing Marek Vasut
2013-11-29 16:46 ` Hector Palacios
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