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SubjectRE: [RESEND v4 4/6] Documentation: misc-devices: Add Documentation for dw-xdata-pcie driver
Hi Krzysztof,

On Sat, Feb 6, 2021 at 23:31:14, Krzysztof Wilczyński <>

> Hi Gustavo,
> [...]
> > +The interaction with this driver is done through the module parameter and
> > +can be changed in runtime. The driver outputs the requested command state
> > +information to /var/log/kern.log or dmesg.
> The driver does not seem to offer any parameters (aside of using sysfs
> for runtime settings), and it also seem to only print what it's doing
> when debug level is enabled - unless I am missing something?
> [...]
> > +Request to stop any current TLP transfer:
> > +- Command:
> > + echo 1 > /sys/kernel/dw-xdata-pcie/stop
> [...]
> When I do the following:
> # echo 1 > /sys/kernel/dw-xdata-pcie/write
> # echo 1 > /sys/kernel/dw-xdata-pcie/stop
> # cat /sys/kernel/dw-xdata-pcie/write
> Would output from cat above simply show "0 MB/s" then? I wonder how
> someone using this new driver could tell whether "write" or "read"
> traffic generation has been enabled aside of reading the sysfs files,
> would adding "/sys/kernel/dw-xdata-pcie/active" be an overkill here?
> What do you think?

Yes, it would display 0 MB/s. This driver is to be used mainly by the
Synopsys DesignWare HW prototyping team. I don't think the general public
will be interested or can use this driver, because requires a special HW
block available only for this prototype.

I tried to reduce to the minimal the interfaces, to avoid possible
confusion. For instance, even the /sys/kernel/dw-xdata-pcie/stop
interface could be avoided, because on the driver unloading or changing
the between write or read it calls the stop procedure.

Due to the nature of the HW block, it only can allow the write or the
read at some given moment, therefore based on the last command enable
write or read, we know which mode is this driving working.
This driver will be used by the testing team on their automation scripts,
thus they will know exactly the sequence input.

Anyway, thanks for your feedback.

> Krzysztof

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