linux-kernel - Re: [PATCH] dmaengine: ti: k3-udma: Do conditional decrement of UDMA_CHAN_RT_PEER_BCNT

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Date:   Tue, 29 Nov 2022 18:27:32 +0200
From:   Péter Ujfalusi <peter.ujfalusi@...il.com>
To:     Jayesh Choudhary <j-choudhary@...com>, vkoul@...nel.org
Cc:     vaishnav.a@...com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: ti: k3-udma: Do conditional decrement of
 UDMA_CHAN_RT_PEER_BCNT_REG



On 28/11/2022 10:50, Jayesh Choudhary wrote:
> PSIL_EP_NATIVE endpoints may not have PEER registers for BCNT and thus
> udma_decrement_byte_counters() should not try to decrement these counters.
> This fixes the issue of crypto IPERF testing where the client side (EVM)
> hangs without transfer of packets to the server side, seen since this
> function was added.

Right, the BCNT is available on PDMA_XY for sure, I don't know if it is 
on AASRC/MCAN type tho, but they are not used right now.

I might clarify and use ep_type == PSIL_EP_PDMA_XY to be sure that only 
the known variant is handled, but this is fine as well.

Acked-by: Peter Ujfalusi <peter.ujfalusi@...il.com>

> 
> Fixes: 7c94dcfa8fcf ("dmaengine: ti: k3-udma: Reset UDMA_CHAN_RT byte counters to prevent overflow")
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> ---
>   drivers/dma/ti/k3-udma.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index ce8b80bb34d7..4c62274e0b33 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -762,11 +762,12 @@ static void udma_decrement_byte_counters(struct udma_chan *uc, u32 val)
>   	if (uc->desc->dir == DMA_DEV_TO_MEM) {
>   		udma_rchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
>   		udma_rchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
> -		udma_rchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
> +		if (uc->config.ep_type != PSIL_EP_NATIVE)
> +			udma_rchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
>   	} else {
>   		udma_tchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
>   		udma_tchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
> -		if (!uc->bchan)
> +		if (!uc->bchan && uc->config.ep_type != PSIL_EP_NATIVE)
>   			udma_tchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
>   	}
>   }

-- 
Péter