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

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Date:   Tue, 28 Jan 2020 12:15:42 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     <vkoul@...nel.org>
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

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?

Thanks,
- Péter

> 
> Regards,
> Peter
> ---
> Peter Ujfalusi (3):
>   dmaengine: ti: k3-udma: Workaround for RX teardown with stale data in
>     peer
>   dmaengine: ti: k3-udma: Move the TR counter calculation to helper
>     function
>   dmaengine: ti: k3-udma: Use the TR counter helper for slave_sg and
>     cyclic
> 
> Vignesh Raghavendra (1):
>   dmaengine: ti: k3-udma: Use ktime/usleep_range based TX completion
>     check
> 
>  drivers/dma/ti/k3-udma.c | 452 +++++++++++++++++++++++++++++----------
>  1 file changed, 343 insertions(+), 109 deletions(-)
> 

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