[PATCH v3 1/1] misc: sram: add dev_pm_ops to support module power gate

[Shenwei Wang]

> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla at arm.com]
> Sent: 2015年8月25日 11:03
> To: Wang Shenwei-B38339
> Cc: Sudeep Holla; gregkh at linuxfoundation.org; arnd at arndb.de; Huang
> Yongcai-B20788; linux-arm-kernel at lists.infradead.org
> Subject: Re: [PATCH v3 1/1] misc: sram: add dev_pm_ops to support module
> power gate
> >> I don't like that solution as it's not scalable with SRAM size and
> >> saving all the content of SRAM just because of few active regions
> >> makes no sense to me at-least. I prefer leaving it to the users to
> >> handle that rather than SRAM driver.
> >
> > I don't think it is not scalable. The choice should be made by the
> > application. From the driver side, it should be able to provide the
> > way to retain its contents during power gate.
> >
> 
> OK that was just my opinion. I just wanted to avoid unnecessary save/restore, e.g.
> if say just few kilobytes are active in say 32MB SRAM, you will save/restore entire
> SRAM ?

Although in theory a SoC can integrate such a big SRAM like 32MB inside, but I don't
think anyone will practice it because the cost is too high. So far, the most popular size
of a SRAM in a SoC is hundreds of KB. 
 
> Anyways, the driver is saving/restoring the memory unconditionally whenever DT
> sets that boolean right ? at-least as the patch stands.

The saving/restoring feature is not enabled by default in this patch. To enable it you
need to add the can-power-gate string in the relating DT node.

Regards,
Shenwei

> Regards,
> Sudeep