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.
WARNING: multiple messages have this Message-ID (diff)
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, 01 Sep 2020 15:40:49 +0000 [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: 20+ 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 15:04 ` Ulf Hansson
2020-09-01 15:06 ` Christoph Hellwig
2020-09-01 15:06 ` Christoph Hellwig
2020-09-01 15:36 ` Ulf Hansson
2020-09-01 15:36 ` Ulf Hansson
2020-09-01 15:40 ` Christoph Hellwig [this message]
2020-09-01 15:40 ` Christoph Hellwig
2020-09-02 8:31 ` Ulf Hansson
2020-09-02 8:31 ` Ulf Hansson
2020-09-02 13:44 ` Rich Felker
2020-09-02 13:44 ` Rich Felker
2020-09-02 15:51 ` Geert Uytterhoeven
2020-09-02 15:51 ` Geert Uytterhoeven
2020-09-03 0:41 ` Rich Felker
2020-09-03 0:41 ` Rich Felker
2020-09-03 8:10 ` Ulf Hansson
2020-09-03 8:10 ` Ulf Hansson
2020-09-02 13:34 ` Rich Felker
2020-09-02 13:34 ` Rich Felker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200901154049.GA376@lst.de \
--to=hch@lst.de \
--cc=broonie@kernel.org \
--cc=dalias@libc.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mmc@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=ulf.hansson@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.