linux-kernel - Re: [PATCH v2 00/32] dmaengine: at_hdmac: Fix concurrency bugs and then convert to virt-dma

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Date:   Fri, 4 Nov 2022 18:52:31 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc:     peda@...ntia.se, du@...ntia.se, maciej.sosnowski@...el.com,
        nicolas.ferre@...rochip.com, mripard@...nel.org,
        torfl6749@...il.com, linux-kernel@...r.kernel.org,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 00/32] dmaengine: at_hdmac: Fix concurrency bugs and
 then convert to virt-dma

On 25-10-22, 12:02, Tudor Ambarus wrote:
> v2:
> - reorder patches so that fixes come first -> easier to backport to
> stable kernels.
> - drop the devm_request_irq() patch as we had to disable the irq anyway
> in remove() in order to avoid spurios IRQs. Using devm variant brings no
> palpable benefit.
> - reword pm_ptr commit message
> 
> 
> at_hdmac driver had poor list handling and concurrency bugs.
> We experienced calling of the completion call twice for the
> same descriptor. Peter Rosin encountered the same while
> reporting a different bug:
> https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/
> 
> Two sets of tests were performed:
> 1/ tested just the fixes, to make sure everything is fine and the
> concurrency bugs are squashed even without the conversion to virt-dma.
> All went fine.
> 2/ tested the entire series including the conversion the virt-dma
> All went fine.
> 
> I tested NAND (prep_dma_memcpy), MMC (prep_dma_slave_sg),
> usart (cyclic mode), dmatest (memcpy, memset).
> With the conversion to virt-dma I replaced the election of a new transfer
> in the tasklet with the election of the new transfer in the interrupt
> handler. We should have a shorter idle window as we remove the scheduling
> latency of the tasklet. Using mtd_speedtest showed similar performances
> when using NAND with DMA. That could be because of using a low timming
> mode on NAND.

This does not apply on dmaengine-fixes, can you please rebase and resend

-- 
~Vinod