From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>,
Vinod Koul <vinod.koul@intel.com>,
Russell King <rmk+kernel@arm.linux.org.uk>,
peter@hurleysoftware.com
Cc: Dan Williams <dan.j.williams@intel.com>,
dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
nsekhar@ti.com, linux-omap@vger.kernel.org,
linux-serial@vger.kernel.org, john.ogness@linutronix.de
Subject: Re: [PATCH 1/3] tty: serial: 8250_omap: do not use RX DMA if pause is not supported
Date: Mon, 10 Aug 2015 14:19:37 +0200 [thread overview]
Message-ID: <55C896D9.5040300@linutronix.de> (raw)
In-Reply-To: <55C890E2.50208@ti.com>
On 08/10/2015 01:54 PM, Peter Ujfalusi wrote:
>> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
>> index 0340ee6ba970..07a11e0935e4 100644
>> --- a/drivers/tty/serial/8250/8250_omap.c
>> @@ -769,7 +771,9 @@ static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
>> return;
>> }
>>
>> - dmaengine_pause(dma->rxchan);
>> + ret = dmaengine_pause(dma->rxchan);
>> + if (WARN_ON_ONCE(ret))
>> + priv->rx_dma_broken = true;
>
> I don't think this is good thing for the stable _and_ for the mainline at the
> same time:
> in stable the rx DMA should not be allowed since the stable kernels does not
> allow pause/resume with omap-dma, so there the rx DMA should be just disabled
> for UART. This change will cause regression since it introduce a WARN_ON_ONCE,
> which will be printed if the user tries to use non working feature.
Okay. We do have pause support in mainline for edma since v4.2-rc1.
This driver can use edma or sdma depending on the configuration. But it
is not yet released. So you suggest remove RX-DMA support completely
from the 8250-omap, mark it stable, and revert that patch once we have
it fixed in sdma?
> In mainline you will eventually going to have pause/resume support so this
> patch will make no sense there.
The way this works is that it has to be fixed upstream before it can be
backported stable. Also Russell made clear (for a good reason) that the
RX problem has to be fixed upstream before he thinks about acking the
SDMA patch.
So if you prefer to instead remove RX-DMA until it is fixed, I am all
yours.
Sebastian
next prev parent reply other threads:[~2015-08-10 12:19 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 20:00 omap-dma + 8250_omap: fix the dmaengine_pause() Sebastian Andrzej Siewior
2015-08-07 20:00 ` [PATCH 1/3] tty: serial: 8250_omap: do not use RX DMA if pause is not supported Sebastian Andrzej Siewior
2015-08-08 0:28 ` Peter Hurley
2015-08-08 9:03 ` Russell King - ARM Linux
2015-08-11 9:57 ` Vinod Koul
2015-08-08 9:32 ` Sebastian Andrzej Siewior
2015-08-08 9:57 ` Russell King - ARM Linux
2015-08-08 15:40 ` Greg KH
2015-08-10 11:54 ` Peter Ujfalusi
2015-08-10 12:19 ` Sebastian Andrzej Siewior [this message]
2015-08-10 13:00 ` Peter Hurley
2015-08-10 17:15 ` Russell King - ARM Linux
2015-08-07 20:00 ` [PATCH 2/3] dma: add __must_check annotation for dmaengine_pause() Sebastian Andrzej Siewior
2015-08-08 0:40 ` Peter Hurley
2015-08-11 9:58 ` Vinod Koul
2015-08-11 10:06 ` Russell King - ARM Linux
2015-08-11 12:34 ` Sebastian Andrzej Siewior
2015-08-21 8:32 ` Vinod Koul
2015-08-07 20:00 ` [PATCH v3 3/3] dma: omap-dma: add support for pause of non-cyclic transfers Sebastian Andrzej Siewior
2015-08-11 12:02 ` Peter Ujfalusi
2015-08-11 12:30 ` Russell King - ARM Linux
2015-08-11 12:43 ` Peter Ujfalusi
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