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Date: Mon, 25 Mar 2024 14:30:10 +0100
Message-Id: <D02V8R59Y6I3.13XIQDA5L6QCK@gmail.com>
Subject: Re: [PATCH v2 RESEND] dmaengine: tegra186: Fix residual calculation
From: "Thierry Reding" <thierry.reding@gmail.com>
To: "Akhil R" <akhilrajeev@nvidia.com>, <ldewangan@nvidia.com>,
 <jonathanh@nvidia.com>, <vkoul@kernel.org>, <dmaengine@vger.kernel.org>,
 <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20240315124411.17582-1-akhilrajeev@nvidia.com>
In-Reply-To: <20240315124411.17582-1-akhilrajeev@nvidia.com>

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On Fri Mar 15, 2024 at 1:44 PM CET, Akhil R wrote:
> The existing residual calculation returns an incorrect value when
> bytes_xfer =3D=3D bytes_req. This scenario occurs particularly with drive=
rs
> like UART where DMA is scheduled for maximum number of bytes and is
> terminated when the bytes inflow stops. At higher baud rates, it could
> request the tx_status while there is no bytes left to transfer. This will
> lead to incorrect residual being set. Hence return residual as '0' when
> bytes transferred equals to the bytes requested.
>
> Fixes: ee17028009d4 ("dmaengine: tegra: Add tegra gpcdma driver")
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
> ---
> v1->v2:
> * corrected typo - s/exisiting/existing/
>
>  drivers/dma/tegra186-gpc-dma.c | 3 +++
>  1 file changed, 3 insertions(+)

Acked-by: Thierry Reding <treding@nvidia.com>

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