From: agross@codeaurora•org (Andy Gross)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] dmaengine: qcom_bam_dma: Add descriptor flag APIs
Date: Thu, 22 May 2014 10:32:14 -0500 [thread overview]
Message-ID: <20140522153214.GB22327@qualcomm.com> (raw)
In-Reply-To: <537E1749.1030505@linaro.org>
On Thu, May 22, 2014 at 04:27:05PM +0100, Srinivas Kandagatla wrote:
<snip>
> >
> >The EOT is not used for every transaction. It is part of a handshaking
> >protocol with the attached peripheral, much like the NWD (notify when done). As
> >near as I can tell today, no peripheral depends on the EOB, so we could drop it
> >for now until it is needed and cross this bridge when we need to.
>
> As EOT behaviour is totally dependent on the attached peripheral(or
> channel), Can't we make this specific to channel by passing
> additional flags in the DT dma channel descriptors? This will be
> better abstraction for drivers as well.
Even for channels where you want to use EOT, you don't use it for every
transaction. So a global channel flag isn't going to work. This is the same
for NWD. It is a per descriptor choice.
>
> I know that EOT flag is part of descriptor but still some channels
> *must* have EOT to run there state-machine correctly. So making it
> optional for those channels might be wrong.
>
> Are there any use cases for particular *channel* where EOT
> requirement changes dynamically?
I2C is one example. You place EOT on the last transaction that makes up a
write/read transaction. You may have multiple descriptors to send data, but the
last one has EOT. And for read transactions, you place NWD on the last read
transaction.
<snip>
--
sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2014-05-22 15:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-17 22:04 [PATCH] dmaengine: qcom_bam_dma: Add descriptor flag APIs Andy Gross
2014-05-02 16:28 ` Vinod Koul
2014-05-02 18:08 ` Andy Gross
2014-05-15 17:32 ` Andy Gross
2014-05-15 19:03 ` Srinivas Kandagatla
2014-05-22 6:10 ` Vinod Koul
2014-05-22 15:09 ` Andy Gross
2014-05-22 15:27 ` Srinivas Kandagatla
2014-05-22 15:32 ` Andy Gross [this message]
2014-05-22 15:56 ` Srinivas Kandagatla
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140522153214.GB22327@qualcomm.com \
--to=agross@codeaurora$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox