From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: linux-renesas-soc@vger.kernel.org,
Koichiro Den <den@valinux.co.jp>, Vinod Koul <vkoul@kernel.org>,
Frank Li <Frank.Li@kernel.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Magnus Damm <magnus.damm@gmail.com>,
dmaengine@vger.kernel.org
Subject: Re: [PATCH 2/3] dmaengine: rcar-dmac: Add missing dma_descriptor_unmap()
Date: Thu, 17 Sep 2026 10:23:07 +0200 [thread overview]
Message-ID: <aqujV8TrgdiZJdEM@ninjato> (raw)
In-Reply-To: <20260917073825.GB4019@killaraus.ideasonboard.com>
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On Thu, Sep 17, 2026 at 10:38:25AM +0300, Laurent Pinchart wrote:
> On Thu, Sep 17, 2026 at 09:12:07AM +0200, Wolfram Sang wrote:
> > From: Koichiro Den <den@valinux.co.jp>
> >
> > Call dma_descriptor_unmap() right after dma_cookie_complete() in the
> > threaded IRQ completion path. Without this, streaming DMA mappings
> > attached to the descriptor are never released and may eventually exhaust
> > DMA mapping resources (e.g. IOVA with an IOMMU or bounce-buffer slots
> > with SWIOTLB), leading to dma_map_* failures.
>
> That looks like a horrible API. It pushes a requirement onto drivers to
> clean up something done by clients, and is completely undocumented.
> Can't those calls be moved somewhere in the DMA engine core ?
In general, I agree. No bandwidth for an API cleanup here, though. It
affects multiple drivers.
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next prev parent reply other threads:[~2026-09-17 8:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 7:12 [PATCH 0/3] dmaengine: rcar-dmac: collection of small missed fixes Wolfram Sang
2026-09-17 7:12 ` [PATCH 1/3] dmaengine: rcar-dmac: Fix PM usage counter imbalance Wolfram Sang
2026-09-17 7:17 ` Laurent Pinchart
2026-09-17 7:12 ` [PATCH 2/3] dmaengine: rcar-dmac: Add missing dma_descriptor_unmap() Wolfram Sang
2026-09-17 7:25 ` sashiko-bot
2026-09-17 7:38 ` Laurent Pinchart
2026-09-17 8:23 ` Wolfram Sang [this message]
2026-09-17 16:39 ` Frank Li
2026-09-18 13:07 ` Koichiro Den
2026-09-27 12:43 ` Wolfram Sang
2026-09-27 13:11 ` Wolfram Sang
2026-09-29 4:13 ` Koichiro Den
2026-09-27 12:38 ` Wolfram Sang
2026-09-17 7:12 ` [PATCH 3/3] dmaengine: rcar-dmac: Remove redundant dev_err()/dev_err_probe() Wolfram Sang
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