From: hector.palacios@digi•com (Hector Palacios)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/3] serial: mxs-auart: implement flush_buffer hook
Date: Fri, 29 Nov 2013 18:49:42 +0100 [thread overview]
Message-ID: <5298D3B6.5050700@digi.com> (raw)
In-Reply-To: <201311291750.22215.marex@denx.de>
Hi Marek,
On 11/29/2013 05:50 PM, Marek Vasut wrote:
> Hello Hector,
>
>> Terminate any DMA transfer and verify the TX FIFO is empty.
>>
>> Signed-off-by: Hector Palacios <hector.palacios@digi•com>
>> ---
>> drivers/tty/serial/mxs-auart.c | 23 +++++++++++++++++++++++
>> 1 file changed, 23 insertions(+)
>>
>> diff --git a/drivers/tty/serial/mxs-auart.c
>> b/drivers/tty/serial/mxs-auart.c index 9f0461778fc1..d9bf6e103f65 100644
>> --- a/drivers/tty/serial/mxs-auart.c
>> +++ b/drivers/tty/serial/mxs-auart.c
>> @@ -782,6 +782,28 @@ static unsigned int mxs_auart_tx_empty(struct
>> uart_port *u) return 0;
>> }
>>
>> +/*
>> + * Flush the transmit buffer.
>> + * Locking: called with port lock held and IRQs disabled.
>> + */
>> +static void mxs_auart_flush_buffer(struct uart_port *u)
>> +{
>> + struct mxs_auart_port *s = to_auart_port(u);
>> + struct dma_chan *channel = s->tx_dma_chan;
>> + unsigned int to;
>> +
>> + if (auart_dma_enabled(s)) {
>> + /* Avoid deadlock with the DMA engine callback */
>> + spin_unlock(&s->port.lock);
>> + dmaengine_terminate_all(channel);
>> + spin_lock(&s->port.lock);
>
> Can you not maybe just set some flag here to tell the DMA engine callback things
> are shutting down and to don't do anything funny anymore ?
I copied these spin_lock protections from the amba-pl011.c driver.
The callbacks in the mxs-auart driver are not taking the lock but I was not sure if
any of the serial core functions they call are, so I thought it was a good idea to
take it.
>> + }
>> + /* Wait for the FIFO to flush */
>> + to = u->timeout;
>> + while (!mxs_auart_tx_empty(u) && to--)
>> + mdelay(1);
>
> Maybe you can put some cond_resched() into the loop to avoid wasting too many
> cycles ?
Do you mean like this? Ok
while (!mxs_auart_tx_empty(u) && to--) {
cond_resched();
mdelay(1);
}
Best regards,
--
Hector Palacios
next prev parent reply other threads:[~2013-11-29 17:49 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 [this message]
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
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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