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From: Kalle Valo <kvalo@kernel.org>
To: Zhenghao Gu <imguzh@gmail.com>
Cc: ath11k@lists.infradead.org,  linux-wireless@vger.kernel.org
Subject: Re: [PATCH v2] wifi: ath11k: fix IOMMU errors on buffer rings
References: <20231212031914.47339-1-imguzh@gmail.com>
Date: Tue, 09 Jan 2024 17:41:46 +0200
In-Reply-To: <20231212031914.47339-1-imguzh@gmail.com> (Zhenghao Gu's message
	of "Mon, 11 Dec 2023 21:19:14 -0600")
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Zhenghao Gu <imguzh@gmail.com> writes:

> virt_to_phys doesn't work on systems with IOMMU enabled,
> which have non-identity physical-to-IOVA mappings.

Can you give an example of such system? Just curious where you are
seeing this.

> It leads to IO_PAGE_FAULTs like this:
> [IO_PAGE_FAULT domain=0x0023 address=0x1cce00000 flags=0x0020]
> and no link can be established.

What do you mean with link in this context? Are you talking about 802.11
association?

> This patch changes that to dma_map_single(), which works correctly.

Good catch. And virt_to_phys() documentation even says this:

 *	This function does not give bus mappings for DMA transfers. In
 *	almost all conceivable cases a device driver should not be using
 *	this function

> Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1
> Signed-off-by: Zhenghao Gu <imguzh@gmail.com>

Jeff, are you ok with this?

I did some cosmetics changes in the pending branch (removed unnecessary
parenthesis, reverse xmas tree etc), please check:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=fefa43d63e1928fce6e8c2bb626900e9ce98ca69

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