Re: [PATCH] platform/powernv: Avoid re-registration of imc debugfs directory

["Oliver O'Halloran" <oohall@gmail.com>]

On Wed, Aug 21, 2019 at 3:37 PM Anju T Sudhakar <anju@linux.vnet.ibm.com> wrote:
>
> Hi,
>
> On 8/21/19 10:16 AM, Oliver O'Halloran wrote:
> > Is there a reason why we create the debugfs directory here and not in
> > opal_imc_counters_probe()? There's logic to remove the debugfs
> > directory in _probe() already so it seems like a more natural place to
> > it.
> >
> Good point. But we can only create the parent directory,
> i.e 'imc' directory in `_probe()` function and the entries can be
> created only here.

I know the entries can't be added in the probe function and I'm not
suggesting they should be.

> The reason is, this debugfs entries are only for
> IMC nest units. So, to get the imc mode and command values from
> the nest memory region we need the relevant offsets from the control
> block structure.
>
> Since imc_get_mem_addr_nest() function reads this address
> for each chip, we invoke the function to create the debugfs
> entries after this values are populated(i.e export_imc_mode_and_cmd() in
> invoked by imc_get_mem_addr_nest()).
>
> Also, if we create the parent directory in `_probe()` function,
> we need to track whether the entries(i.e imc_cmd and imc_mode) are
> created or not.

I think you should be tracking this anyway so you can do proper
cleanup if a debugfs entry can't be added. The current approach of
nuking the entire debugfs directory is pretty questionable.

> Regards,
>
> Anju
>