Re: Atmel UART with dma enabled does not work on branch 5.4.Y from version 5.4.174.

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Feb 18, 2022 at 09:40:55AM +0100, Mickael GARDET wrote:
> Hi,
> 
> we observed a regression on our atmel platforms on branch 5.4.Y from version
> 5.4.174.
> uarts are no longer functional if DMA is enabled.
> 
> the following patch
> Commit e6af9b05bec63cd4d1de2a33968cd0be2a91282a dmaengine: at_xdmac: Start
> transfer for cyclic channels in issue_pending
> Link:
> https://lore.kernel.org/r/20211215110115.191749-3-tudor.ambarus@microchip.com
> has not been backported but is needed if the patch
> Commit 4f4b9b5895614eb2e2b5f4cab7858f44bd113e1b tty: serial: atmel: Call
> dma_async_issue_pending()
> Link:
> https://lore.kernel.org/r/20211125090028.786832-4-tudor.ambarus@microchip.com
> is applied.
> 
> enclosed commit fix this issue and work for me.
> 
> Best regards,
> Mickael GARDET
> 
> From 9877f93c066be8c2f4e33a6edd4dfa3d6d6974d9 Mon Sep 17 00:00:00 2001
> From: Tudor Ambarus <tudor.ambarus@microchip.com>
> Date: Wed, 15 Dec 2021 13:01:05 +0200
> Subject: [PATCH] dmaengine: at_xdmac: Start transfer for cyclic channels in
> issue_pending
> 
> commit e6af9b05bec63cd4d1de2a33968cd0be2a91282a upstream.
> 
> Cyclic channels must too call issue_pending in order to start a transfer.
> Start the transfer in issue_pending regardless of the type of channel.
> This wrongly worked before, because in the past the transfer was started
> at tx_submit level when only a desc in the transfer list.
> 
> Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended
> DMA Controller driver")
> Change-Id: If1bf3e13329cebb9904ae40620f6cf2b7f06fe9f
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> Link:
> https://lore.kernel.org/r/20211215110115.191749-3-tudor.ambarus@microchip.com
> Signed-off-by: Vinod Koul <vkoul@kernel.org>
> ---
> drivers/dma/at_xdmac.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index f63d141481a3..9aae6b3da356 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -1726,11 +1726,13 @@ static irqreturn_t at_xdmac_interrupt(int irq,
> void *dev_id)
> static void at_xdmac_issue_pending(struct dma_chan *chan)
> {
> struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
> +    unsigned long flags;
> 
> dev_dbg(chan2dev(&atchan->chan), "%s\n", __func__);
> 
> -    if (!at_xdmac_chan_is_cyclic(atchan))
> -        at_xdmac_advance_work(atchan);
> +    spin_lock_irqsave(&atchan->lock, flags);
> +    at_xdmac_advance_work(atchan);
> +    spin_unlock_irqrestore(&atchan->lock, flags);
> 
> return;
> }
> 
> base-commit: 7b3eb66d0daf61e91cccdb2fe5d271ae5adc5a76
> 
> -- 
> 2.35.1
> 

The patch is whitespace damaged and can not be applied at all :(

Can you try fixing your email client up, or worst case, attach the
patch, and we can take it from there?

Also be sure to sign-off on the patch, as you have modified it to work
properly on this branch.

thanks,

greg k-h