linux-kernel - Re: [PATCH v1 06/12] serial: 8250_dma: stop ongoing RX DMA on exception

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Message-ID: <CAHp75VdYEEwBx+G=2D_q5M1DpUWsyHn9JZbYhb4GQeJNJwv9yw@mail.gmail.com>
Date:	Fri, 8 Apr 2016 11:07:39 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Vinod Koul <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dmaengine <dmaengine@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Puustinen, Ismo" <ismo.puustinen@...el.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v1 06/12] serial: 8250_dma: stop ongoing RX DMA on exception

On Fri, Apr 8, 2016 at 2:54 AM, Peter Hurley <peter@...leysoftware.com> wrote:
> On 04/07/2016 01:37 PM, Andy Shevchenko wrote:
>> If we get an exeption interrupt. i.e. UART_IIR_RLSI, stop any ongoing RX DMA
>> transfer otherwise it might generates more spurious interrupts and make port
>> unavailable anymore.
>
> Then how to know which rx byte the error is for if dma continues anyway?
> What if there are multiple error bytes?

And how should it work?
We get an interrupt during DMA, if we don't stop DMA it will be racy
with direct readings.

>
>
>> As has been seen on Intel Broxton system:
>
> This system shouldn't be setup for UART DMA imo.

Same approach is done in 8250_omap.

-- 
With Best Regards,
Andy Shevchenko