linux-kernel - Re: [PATCH v7 12/19] dmaengine: tegra-apb: Remove handling of unrealistic error condition

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Date:   Tue, 4 Feb 2020 11:52:41 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 12/19] dmaengine: tegra-apb: Remove handling of
 unrealistic error condition


On 02/02/2020 22:28, Dmitry Osipenko wrote:
> The pending_sg_req list can't ever be empty because:
> 
> 1. If it was empty, then handle_cont_sngl_cycle_dma_done() shall crash
>    before of handle_continuous_head_request() invocation.
> 
> 2. The handle_cont_sngl_cycle_dma_done() can't happen after stopping DMA.

By this you mean calling terminate_all?

> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/dma/tegra20-apb-dma.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 62d181bd5e62..c7dc27ef1856 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -564,12 +564,6 @@ static bool handle_continuous_head_request(struct tegra_dma_channel *tdc,
>  {
>  	struct tegra_dma_sg_req *hsgreq;
>  
> -	if (list_empty(&tdc->pending_sg_req)) {
> -		dev_err(tdc2dev(tdc), "DMA is running without req\n");
> -		tegra_dma_stop(tdc);
> -		return false;
> -	}
> -
>  	/*
>  	 * Check that head req on list should be in flight.
>  	 * If it is not in flight then abort transfer as
> 

There is also a list_empty() check in tdc_configure_next_head_desc()
which is also redundant and could be removed here as well.

Jon

-- 
nvpublic