From mboxrd@z Thu Jan  1 00:00:00 1970
From: bigeasy@linutronix.de (Sebastian Andrzej Siewior)
Date: Wed, 17 Sep 2014 18:34:45 +0200
Subject: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround
 for AM33xx
In-Reply-To: <54118AAB.2010205@linutronix.de>
References: <1410377411-26656-1-git-send-email-bigeasy@linutronix.de>
 <1410377411-26656-10-git-send-email-bigeasy@linutronix.de>
 <20140911111721.GB17476@xps8300> <54118AAB.2010205@linutronix.de>
Message-ID: <5419B825.5000201@linutronix.de>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org
Archived-At: <https://lore.kernel.org/linux-arm-kernel/5419B825.5000201@linutronix.de/>
List-Archive: <https://lore.kernel.org/linux-arm-kernel/>
List-Post: <mailto:linux-arm-kernel@lists.infradead.org>

On 09/11/2014 01:42 PM, Sebastian Andrzej Siewior wrote:
>> We should add hooks like tx_dma and rx_dma to struct uart_8250_dma so
>> that the probe drivers can replace serial8250_tx_dma and
>> seria8250_rx_dma, like I think Alan already suggested.
> 
> Okay. Wasn't aware that Alan already suggested that.
> I also need a watchdog timer for TX since it seems that on omap3 the
> DMA engine suddenly forgets to continue with DMA?
> 
> If this is really what we want, I would need to refactor a few things?
> 
>> Let's keep serial8250_tx_dma/rx_dma as the default, and not add any
>> quirks to them. Only if there is a very common case should it be
>> handled in those. The case of RX req needing to be sent before data in
>> FIFO maybe one of those, but I'm no sure.
> 
> keep in mind that both (RX & TX bugs/hacks) need also a bit of handling
> in the 8250-core so it works together (like the tx_err member so we
> fall back to manual xmit)

Done. I've kept the RX workarounds in the 8250_dma and moved the TX
part into the omap driver.
I needed to add the 8250_core pieces of patch #10 [0]. Now If you say,
couldn't this done in an other way then I could move the RX workarounds
pieces to the omap driver as well as the interrupt routine. Any
preferences?

[0] [PATCH 10/16] tty: serial: 8250_dma: optimize the xmit path due to
    UART_BUG_DMA_TX

Sebastian