On 20/01/2020 11.01, Geert Uytterhoeven wrote:
> Hi Peter,
>
> On Fri, Jan 17, 2020 at 9:08 PM Peter Ujfalusi <peter.ujfalusi@xxxxxx> 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@xxxxxxxxx>
>>> ---
>>> 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
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