linux-kernel - Re: [PATCH] ASoC: loongson: fix address space confusion

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Message-ID: <ZJlFHtmJE6vPyT0k@infradead.org>
Date:   Mon, 26 Jun 2023 00:58:22 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Yingkun Meng <mengyingkun@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: loongson: fix address space confusion

On Thu, Jun 22, 2023 at 12:12:22PM +0200, Arnd Bergmann wrote:
> Change the driver to instead use the physical address as stored in the
> PCI BAR resource directly. Since 'dev_addr' is a 32-bit address, I think
> this results in the same truncated address on loongarch but is otherwise
> closer to portable code and avoids the warning.

This gets rid of the warning, but is still broken.
pci_resource_start retuns a resource_size_t, which really is a
phys_addr_t, but certainly no DMA address.  To map PCI(e) resources
for DMA the driver needs to call dma_map_resource.