From: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jun Nie <jun.nie@linaro.org>,
"ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"adrian.hunter@intel.com" <adrian.hunter@intel.com>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>
Subject: Re: [PATCH 4/4] mmc: sdhci: Add DMA memory boundary workaround
Date: Wed, 4 Dec 2019 07:11:04 +0000 [thread overview]
Message-ID: <20191204145709.34e42f56@xhacker.debian> (raw)
In-Reply-To: <20191203130609.GA2144@infradead.org>
Hi Christoph
On Tue, 3 Dec 2019 05:06:09 -0800 Christoph Hellwig wrote:
>
> On Tue, Dec 03, 2019 at 09:49:49AM +0000, Jisheng Zhang wrote:
> > > As in exactly one boundary and not an alignment? Where the one
> > > boundary is not a power of two and thus can't be expressed?
> >
> > Take drivers/mmc/host/sdhci-of-dwcmshc.c for example, target physical DMA addr
> > can't span 128MB, 256MB, 128*3MB, ...128*nMB
> >
> > I'm not sure whether blk_queue_segment_boundary could solve this limitation.
>
> That is exaxtly the kind of limitation blk_queue_segment_boundary is
> intended for.
Until after dma_map_sg(), we can't know the physical DMA address range, so
how does block layer know and check the DMA range beforehand? I'm a newbie on
block layer, could you please teach me? At the same time
I'm reading the code as well.
Thanks in advance
prev parent reply other threads:[~2019-12-04 7:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191202144104.5069-1-jun.nie@linaro.org>
[not found] ` <20191202144104.5069-5-jun.nie@linaro.org>
[not found] ` <20191203103320.273a7309@xhacker.debian>
[not found] ` <CABymUCMVi_N2Mt82YDt7wrys4Z_vnXYEu15-YBa+S1CejT9iZw@mail.gmail.com>
[not found] ` <20191203165123.4e6f9e28@xhacker.debian>
2019-12-03 9:18 ` [PATCH 4/4] mmc: sdhci: Add DMA memory boundary workaround Christoph Hellwig
2019-12-03 9:49 ` Jisheng Zhang
2019-12-03 13:06 ` Christoph Hellwig
2019-12-04 7:11 ` Jisheng Zhang [this message]
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