From: Christoph Hellwig <hch@lst.de>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Christoph Hellwig <hch@lst.de>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Rich Felker <dalias@libc.org>, Mark Brown <broonie@kernel.org>,
Linux-sh list <linux-sh@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] mmc: mmc_spi: Allow the driver to be built when CONFIG_HAS_DMA is unset
Date: Tue, 1 Sep 2020 17:40:49 +0200 [thread overview]
Message-ID: <20200901154049.GA376@lst.de> (raw)
In-Reply-To: <CAPDyKFqZXdtVokrDQvJAh-NzN0T2ayPD6MepemLEaDt1TRPduw@mail.gmail.com>
On Tue, Sep 01, 2020 at 05:36:17PM +0200, Ulf Hansson wrote:
> > I still don't think this makes sense, as the dma_mask should always
> > be non-NULL here.
>
> If that is the case, I wonder how the driver could even have worked without DMA.
>
> Because in the existing code, host->dma_dev gets assigned to
> spi->master->dev.parent->dma_mask - which seems to turn on the DMA
> usage in the driver.
>
> What am I missing?
Do you know of other non-DMA users? For SH nommu it probably worked
because SH nommu used to provide a DMA implementation that worked
fine for streaming maps, but was completely broken for coherent
allocation. And this driver appears to only use the former.
next prev parent reply other threads:[~2020-09-01 16:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 15:04 [PATCH v2] mmc: mmc_spi: Allow the driver to be built when CONFIG_HAS_DMA is unset Ulf Hansson
2020-09-01 15:06 ` Christoph Hellwig
2020-09-01 15:36 ` Ulf Hansson
2020-09-01 15:40 ` Christoph Hellwig [this message]
2020-09-02 8:31 ` Ulf Hansson
2020-09-02 13:44 ` Rich Felker
2020-09-02 15:51 ` Geert Uytterhoeven
2020-09-03 0:41 ` Rich Felker
2020-09-03 8:10 ` Ulf Hansson
2020-09-02 13:34 ` Rich Felker
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