Re: [PATCH] platform/x86: Add Intel ISP dummy driver

[Hans de Goede]

Hi,


On 29-08-18 20:20, Andy Shevchenko wrote:
> On Wed, Aug 29, 2018 at 03:57:44PM +0200, Hans de Goede wrote:
> > The Image Signal Processor found on Cherry Trail devices is brought up in
> > D0 state on devices which have camera sensors attached to it. The ISP will
> > not enter D3 state again without some massaging of its registers beforehand
> > and the ISP not being in D3 state blocks the SoC from entering S0ix modes.
> >
> > There was a driver for the ISP in drivers/staging but that got removed
> > again because it never worked. It does not seem likely that a real
> > driver for the ISP will be added to the mainline kernel anytime soon.
> >
> > This commit adds a dummy driver which contains the necessary magic from
> > the staging driver to powerdown the ISP, so that Cherry Trail devices where
> > the ISP is used will properly use S0ix modes when suspended.
> >
> > Together with other recent S0ix related fixes this allows S0ix modes to
> > be entered on e.g. a Chuwi Hi8 Pro and a HP x2 210.
>
> Thanks for the patch, my comments below.

Thank you for the review and sorry for being a bit slow with responding
I've been quite busy with other stuff.

> >   drivers/platform/x86/intel_isp_dummy.c | 119 +++++++++++++++++++++++++
>
> First of all, I would like to see that this is about pm and pm only, so,
> perhaps
>
> intel_isp_pm ?
>
> OTOH, it would be nice to have less confusing of what ISP we are talking about,
> so,
>
> intel_atomisp2_pm ?

Works for me, intel_atomisp2_pm it is for v2 of this patch.

> > +config INTEL_ISP_DUMMY
> > +	tristate "Intel ISP dummy driver"
>
> > +	depends on PCI && IOSF_MBI && PM
>
> If someone decides to port this to kernels where ATOMISP driver is still
> available, it might be a conflict here. I dunno if it's a good idea to put
> something like depends !ATOMISP here taking into consideration that it would be
> staled option.

I don't look adding deps / conflucts on options which are
not present upstream, so I'm going to keep this as for v2.

> > +	while (1) {
>
> A nit: I would rather put it like
>
> do {
> ...
> } while (time_after(...));

That would need to be time_before then, since the time check is a timeout
and then I would need to re-check the time outside the loop to see if
a timeout happened. So I believe it would better to keep this as is.


> > +		/* Wait until ISPSSPM0 bit[25:24] shows 0x3 */
> > +		iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, ISPSSPM0, &val);
> > +		val = (val & ISPSSPM0_ISPSSS_MASK) >> ISPSSPM0_ISPSSS_OFFSET;
> > +		if (val == ISPSSPM0_IUNIT_POWER_OFF)
> > +			break;
> > +
> > +		if (time_after(jiffies, timeout)) {
> > +			dev_err(&dev->dev, "IUNIT power-off timeout.\n");
> > +			return -EBUSY;
> > +		}
> > +		usleep_range(1000, 2000);
> > +	}

Regards,

Hans