Subject: [PATCH 06/17] gpio: mvebu: add suspend/resume support

From: [email-masked] (David Cohen)
Date: Mon, 27 Oct 2014 10:45:52 -0700

On Mon, Oct 27, 2014 at 02:27:16PM +0900, Alexandre Courbot wrote:
> On Sat, Oct 25, 2014 at 5:45 AM, Andrew Lunn <[email-masked]> wrote:
> >> > +   switch (mvchip->soc_variant) {
> >> > +   case MVEBU_GPIO_SOC_VARIANT_ORION:
> >> > +           mvchip->edge_mask_regs[0] =
> >> > +                   readl(mvchip->membase + GPIO_EDGE_MASK_OFF);
> >> > +           mvchip->level_mask_regs[0] =
> >> > +                   readl(mvchip->membase + GPIO_LEVEL_MASK_OFF);
> >> > +           break;
> >> > +   case MVEBU_GPIO_SOC_VARIANT_MV78200:
> >> > +           for (i = 0; i < 2; i++) {
> >> > +                   mvchip->edge_mask_regs[i] =
> >> > +                           readl(mvchip->membase +
> >> > +                                 GPIO_EDGE_MASK_MV78200_OFF(i));
> >> > +                   mvchip->level_mask_regs[i] =
> >> > +                           readl(mvchip->membase +
> >> > +                                 GPIO_LEVEL_MASK_MV78200_OFF(i));
> >> > +           }
> >> > +           break;
> >> > +   case MVEBU_GPIO_SOC_VARIANT_ARMADAXP:
> >> > +           for (i = 0; i < 4; i++) {
> >> > +                   mvchip->edge_mask_regs[i] =
> >> > +                           readl(mvchip->membase +
> >> > +                                 GPIO_EDGE_MASK_ARMADAXP_OFF(i));
> >> > +                   mvchip->level_mask_regs[i] =
> >> > +                           readl(mvchip->membase +
> >> > +                                 GPIO_LEVEL_MASK_ARMADAXP_OFF(i));
> >> > +           }
> >> > +           break;
> >> > +   default:
> >> > +           BUG();
> >>
> >> Isn't it too severe? Is the platform going too unstable if driver
> >> reaches this case?
> >> I'd consider a WARN() instead.
> >
> > This is a common pattern in this driver. So i guess Thomas just
> > cut/pasted the switch statement from _probe(), which also has the
> > BUG().
> >
> > Given that _probe() should of thrown a BUG() in this situation, if it
> > happens here, it means mvchip->soc_variant has been corrupted, and so
> > bad things are happening. So a BUG() is maybe called for?
> 
> I agree that BUG() is adequate here. probe() should recognize the
> exact same set of chips - if we reach this point this means that
> either the data has been corrupted or we added support for a new chip
> in probe() and forgot suspend/resume. In both cases the driver should
> express its discontent.

Just for the records, since I don't know this platform very well :)

IMHO unless this issue is the source of a serious instability or data
corruption, a WARN() would be a better way for the driver express its
discontent. It's way better to have a functional platform for further
debugging.

This driver can also be compiled as a module. I wonder if it's a good
behavior boot the platform and then crash the kernel when loading the
module driver.

But anyway, that would be just me.

Br, David Cohen

> 
> Acked-by: Alexandre Courbot <[email-masked]>