linux-kernel - Re: regression: 3a878c430fd6 ("tty: serial: msm: Add TX DMA support") drops data

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Date:	Wed, 20 Apr 2016 09:07:19 +0300
From:	Ivan Ivanov <iivanov.xz@...il.com>
To:	frowand.list@...il.com
Cc:	Andy Gross <agross@...eaurora.org>,
	David Brown <davidb@...eaurora.org>,
	srinivas.kandagatla@...aro.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	jslaby@...e.com, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	linux-soc@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: regression: 3a878c430fd6 ("tty: serial: msm: Add TX DMA support") drops data


> On Apr 20, 2016, at 02:23, Frank Rowand <frowand.list@...il.com> wrote:
> 
> Hi Ivan,
> 
> It appears that I have found a regression caused by
> 3a878c430fd6 ("tty: serial: msm: Add TX DMA support").
> 
> When I cat a file slightly larger than 126000 bytes on
> the console, viewed via minicom connected to the serial
> port, I am losing random chunks of data, almost always
> three bytes in length.  I have also seen a lost chunk
> of two bytes.
> 
> I am using the 8074 dragonboard, with the dts of
> arch/arm/boot/dts/qcom-apq8074-dragonboard.dts.
> The dts node is serial@...1e000, which has a
> compatible of "qcom,msm-uartdm-v1.4", so is_uartdm
> should be UARTDM_1P4.

I don’t remember what was biggest chunk, which DMA
could carry, sorry. Are you using DMA or just PIO? 
Is this happening only with cat and terminal or even
when you send data in other means. I believe that 
people from Linaro could help you better.

Regards,
Ivan