From: Rui Wang <wr574332525@163.com>
To: frank.li@oss.nxp.com
Cc: vkoul@kernel.org, dmaengine@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] dmaengine: dw-axi-dmac: report paused state and residue in tx_status
Date: Mon, 28 Sep 2026 11:51:21 +0800 [thread overview]
Message-ID: <20260928035121.2033-1-wr574332525@163.com> (raw)
In-Reply-To: <arVuKmKc8XE46R9B@SMW015318>
Hi Frank,
On Thu, Sep 24, 2026 at 01:38:34PM -0500, Frank Li wrote:
> Look like possible. Caller may reuse prevous DMA buffer. But I don't know
> how to resolve it.
How about pre-loading the pointer registers when programming the
channel? In v6, axi_chan_block_xfer_start() writes the first block's
SAR/DAR into CH_SAR/CH_DAR before setting the channel enable bit. The
hardware reloads them with the same values once it fetches the first
LLI, and in the window in between a reader observes the start of the
first block, i.e. a full residue, which is the truth for a transfer
that has not begun. A stale end-of-transfer pointer left by a previous
run can no longer be observed, so the buffer-reuse race is closed at
the source and tx_status stays free of special cases.
Best regards,
Rui Wang
prev parent reply other threads:[~2026-09-28 3:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 2:57 [PATCH v5] dmaengine: dw-axi-dmac: report paused state and residue in tx_status Rui Wang
2026-09-24 3:18 ` sashiko-bot
2026-09-24 18:38 ` Frank Li
2026-09-28 3:51 ` Rui Wang [this message]
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