From: Vinod Koul <vinod.koul@intel.com>
To: Jiada Wang <jiada_wang@mentor.com>
Cc: dan.j.williams@intel.com, dmaengine@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] dma: imx-sdma: add 1ms delay to ensure SDMA channel is stopped
Date: Mon, 13 Feb 2017 15:52:55 +0530 [thread overview]
Message-ID: <20170213102254.GK2843@localhost> (raw)
In-Reply-To: <e1cd4749-7c66-b918-abc5-7f9e24cd2ff0@mentor.com>
On Mon, Feb 13, 2017 at 03:30:19PM +0900, Jiada Wang wrote:
> >>+static int sdma_disable_channel_with_delay(struct dma_chan *chan)
> >>+{
> >>+ sdma_disable_channel(chan);
> >>+ mdelay(1);
> >
> >what is the gaurantee that 1ms is fine? Shouldn't you poll the bit to see
> >channel is disabled properly..
> >
> I got the information from NXP (freescale) R&D team,
> according to them, by write '1' to SDMA_H_STATSTOP, only disables
> the related sdma channel (so poll HE bit will indicates the channel
> has been disabled),
> but it cannot ensure SDMA core stop to access modules' FIFO,
> SDMA core may still is running, this is a bug in HW.
Okay b ut you are not doing the HE bit here..??
>
> regarding if the '1ms' is enough to ensure SDMA core has stopped,
> NXP R&D team mentioned:
> "we should add some delay of one BD SDMA cost time after disable the
> channel bit, the maximum is 1ms"
> so I assume 1ms should work for all cases
At least please document this in changelog and comments in code.
--
~Vinod
next prev parent reply other threads:[~2017-02-13 10:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-10 14:46 [PATCH 1/1] dma: imx-sdma: add 1ms delay to ensure SDMA channel is stopped jiada_wang
2017-02-13 2:05 ` Vinod Koul
2017-02-13 6:30 ` Jiada Wang
2017-02-13 10:22 ` Vinod Koul [this message]
2017-03-01 8:14 ` Jiada Wang
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=20170213102254.GK2843@localhost \
--to=vinod.koul@intel.com \
--cc=dan.j.williams@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=jiada_wang@mentor.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.