linux-kernel - Re: [PATCH net] net: ethernet: ti: am65-cpsw: Add RX DMA Channel Teardown Quirk

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Date:   Thu, 9 Feb 2023 15:33:42 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Siddharth Vadapalli <s-vadapalli@...com>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, linux@...linux.org.uk,
        pabeni@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, vigneshr@...com, srk@...com
Subject: Re: [PATCH net] net: ethernet: ti: am65-cpsw: Add RX DMA Channel
 Teardown Quirk



On 09/02/2023 10:44, Siddharth Vadapalli wrote:
> In TI's AM62x/AM64x SoCs, successful teardown of RX DMA Channel raises an
> interrupt. The process of servicing this interrupt involves flushing all
> pending RX DMA descriptors and clearing the teardown completion marker
> (TDCM). The am65_cpsw_nuss_rx_packets() function invoked from the RX
> NAPI callback services the interrupt. Thus, it is necessary to wait for
> this handler to run, drain all packets and clear TDCM, before calling
> napi_disable() in am65_cpsw_nuss_common_stop() function post channel
> teardown. If napi_disable() executes before ensuring that TDCM is
> cleared, the TDCM remains set when the interfaces are down, resulting in
> an interrupt storm when the interfaces are brought up again.
> 
> Since the interrupt raised to indicate the RX DMA Channel teardown is
> specific to the AM62x and AM64x SoCs, add a quirk for it.
> 
> Fixes: 4f7cce272403 ("net: ethernet: ti: am65-cpsw: add support for am64x cpsw3g")
> Co-developed-by: Vignesh Raghavendra <vigneshr@...com>
> Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>

Reviewed-by: Roger Quadros <rogerq@...nel.org>