linux-kernel - Re: [PATCH for-next 0/4] dmaengine: ti: k3-udma: Updates for next

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Message-ID: <20200128115006.GT2841@vkoul-mobl>
Date:   Tue, 28 Jan 2020 17:20:06 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        dan.j.williams@...el.com, grygorii.strashko@...com, vigneshr@...com
Subject: Re: [PATCH for-next 0/4] dmaengine: ti: k3-udma: Updates for next

On 28-01-20, 12:15, Peter Ujfalusi wrote:
> Vinod,
> 
> On 27/01/2020 15.21, Peter Ujfalusi wrote:
> > Hi Vinod,
> > 
> > Based on customer reports we have identified two issues with the UDMA driver:
> > 
> > TX completion (1st patch):
> > The scheduled work based workaround for checking for completion worked well for
> > UART, but it had significant impact on SPI performance.
> > The underlying issue is coming from the fact that we have split data movement
> > architecture.
> > In order to know that the transfer is really done we need to check the remote
> > end's (PDMA) byte counter.
> > 
> > RX channel teardown with stale data in PDMA (2nd patch):
> > If we try to stop the RX DMA channel (teardown) then PDMA is trying to flush the
> > data is might received from a peripheral, but if UDMA does not have a packet to
> > use for this draining than it is going to push back on the PDMA and the flush
> > will never completes.
> > The workaround is to use a dummy descriptor for flush purposes when the channel
> > is terminated and we did not have active transfer (no descriptor for UDMA).
> > This allows UDMA to drain the data and the teardown can complete.
> > 
> > The last two patch is to use common code to set up the TR parameters for
> > slave_sg, cyclic and memcpy. The setup code is the same as we used for memcpy
> > with the change we can handle 4.2GB sg elements and periods in case of cyclic.
> > It is also nice that we have single function to do the configuration.
> 
> I have marked these patches as for-next as 5.5 was not released yet.
> Would it be possible to have these as fixes for 5.6?

Sure but are they really fixes, why cant they go for next release :)

They seem to improve things for sure, but do we want to call them as
fixes..?

-- 
~Vinod