From: Peter Ujfalusi <peter.ujfalusi@ti.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
Vinod Koul <vkoul@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
<dmaengine@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] dmaengine: Create symlinks between DMA channels and slaves
Date: Mon, 20 Jan 2020 12:16:33 +0200 [thread overview]
Message-ID: <1cdc4f71-f365-8c9e-4634-408c59e6a3f9@ti.com> (raw)
In-Reply-To: <CAMuHMdVzQCWvH-LJ9ME5dRyafudZBHQLaJQzkSCPnughv_q2aA@mail.gmail.com>
On 20/01/2020 11.01, Geert Uytterhoeven wrote:
> Hi Peter,
>
> On Fri, Jan 17, 2020 at 9:08 PM Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
>> On 1/17/20 5:30 PM, Geert Uytterhoeven wrote:
>>> Currently it is not easy to find out which DMA channels are in use, and
>>> which slave devices are using which channels.
>>>
>>> Fix this by creating two symlinks between the DMA channel and the actual
>>> slave device when a channel is requested:
>>> 1. A "slave" symlink from DMA channel to slave device,
>>
>> Have you considered similar link name as on the slave device:
>> slave:<name>
>>
>> That way it would be easier to grasp which channel is used for what
>> purpose by only looking under /sys/class/dma/ and no need to check the
>> slave device.
>
> Would this really provide more information?
> The device name is already provided in the target of the symlink:
>
> root@koelsch:~# readlink
> /sys/devices/platform/soc/e6720000.dma-controller/dma/dma1chan2/slave
> ../../../ee140000.sd
e6720000.dma-controller/dma/dma1chan2/slave -> ../../../ee140000.sd
e6720000.dma-controller/dma/dma1chan3/slave -> ../../../ee140000.sd
It is hard to tell which one is the tx and RX channel without looking
under the ee140000.sd:
ee140000.sd/dma:rx -> ../e6720000.dma-controller/dma/dma1chan3
ee140000.sd/dma:tx -> ../e6720000.dma-controller/dma/dma1chan2
Another option would be to not have symlinks, but a debugfs file where
this information can be extracted and would only compiled if debugfs is
enabled.
>>> 2. A "dma:<name>" symlink slave device to DMA channel.
>>> When the channel is released, the symlinks are removed again.
>>> The latter requires keeping track of the slave device and the channel
>>> name in the dma_chan structure.
>>>
>>> Note that this is limited to channel request functions for requesting an
>>> exclusive slave channel that take a device pointer (dma_request_chan()
>>> and dma_request_slave_channel*()).
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>> ---
>>> v2:
>>> - Add DMA_SLAVE_NAME macro,
>>> - Also handle channels from FIXME,
>>> - Add backlinks from slave device to DMA channel,
>>>
>>> On r8a7791/koelsch, the following new symlinks are created:
>>>
>>> /sys/devices/platform/soc/
>>> ├── e6700000.dma-controller/dma/dma0chan0/slave -> ../../../e6e20000.spi
>>> ├── e6700000.dma-controller/dma/dma0chan1/slave -> ../../../e6e20000.spi
>>> ├── e6700000.dma-controller/dma/dma0chan2/slave -> ../../../ee100000.sd
>>> ├── e6700000.dma-controller/dma/dma0chan3/slave -> ../../../ee100000.sd
>>> ├── e6700000.dma-controller/dma/dma0chan4/slave -> ../../../ee160000.sd
>>> ├── e6700000.dma-controller/dma/dma0chan5/slave -> ../../../ee160000.sd
>>> ├── e6700000.dma-controller/dma/dma0chan6/slave -> ../../../e6e68000.serial
>>> ├── e6700000.dma-controller/dma/dma0chan7/slave -> ../../../e6e68000.serial
>>> ├── e6720000.dma-controller/dma/dma1chan0/slave -> ../../../e6b10000.spi
>>> ├── e6720000.dma-controller/dma/dma1chan1/slave -> ../../../e6b10000.spi
>>> ├── e6720000.dma-controller/dma/dma1chan2/slave -> ../../../ee140000.sd
>>> ├── e6720000.dma-controller/dma/dma1chan3/slave -> ../../../ee140000.sd
>>> ├── e6b10000.spi/dma:rx -> ../e6720000.dma-controller/dma/dma1chan1
>>> ├── e6b10000.spi/dma:tx -> ../e6720000.dma-controller/dma/dma1chan0
>>> ├── e6e20000.spi/dma:rx -> ../e6700000.dma-controller/dma/dma0chan1
>>> ├── e6e20000.spi/dma:tx -> ../e6700000.dma-controller/dma/dma0chan0
>>> ├── e6e68000.serial/dma:rx -> ../e6700000.dma-controller/dma/dma0chan7
>>> ├── e6e68000.serial/dma:tx -> ../e6700000.dma-controller/dma/dma0chan6
>>> ├── ee100000.sd/dma:rx -> ../e6700000.dma-controller/dma/dma0chan3
>>> ├── ee100000.sd/dma:tx -> ../e6700000.dma-controller/dma/dma0chan2
>>> ├── ee140000.sd/dma:rx -> ../e6720000.dma-controller/dma/dma1chan3
>>> ├── ee140000.sd/dma:tx -> ../e6720000.dma-controller/dma/dma1chan2
>>> ├── ee160000.sd/dma:rx -> ../e6700000.dma-controller/dma/dma0chan5
>>> └── ee160000.sd/dma:tx -> ../e6700000.dma-controller/dma/dma0chan4
>
>
> Gr{oetje,eeting}s,
>
> Geert
>
- Péter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
next prev parent reply other threads:[~2020-01-20 10:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 15:30 [PATCH v2] dmaengine: Create symlinks between DMA channels and slaves Geert Uytterhoeven
2020-01-17 16:26 ` Niklas Söderlund
2020-01-17 20:10 ` Peter Ujfalusi
2020-01-20 9:01 ` Geert Uytterhoeven
2020-01-20 10:16 ` Peter Ujfalusi [this message]
2020-01-20 10:51 ` Geert Uytterhoeven
2020-01-20 12:06 ` Peter Ujfalusi
2020-01-21 20:22 ` Geert Uytterhoeven
2020-01-22 9:40 ` Vinod Koul
2020-01-24 6:13 ` Vinod Koul
2020-01-24 7:31 ` Peter Ujfalusi
2020-01-27 5:08 ` Vinod Koul
[not found] ` <CGME20200129174723eucas1p1fe4f76325f463fc9e3645ce18740d2eb@eucas1p1.samsung.com>
2020-01-29 17:47 ` Marek Szyprowski
2020-01-30 8:30 ` Geert Uytterhoeven
2020-01-30 10:33 ` Marek Szyprowski
2020-01-30 10:47 ` Geert Uytterhoeven
2020-01-30 9:43 ` Peter Ujfalusi
2020-01-30 9:51 ` Geert Uytterhoeven
2020-01-30 10:22 ` Peter Ujfalusi
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