[PATCH 2/8] soc: imx: gpc: fix the wrong using of regmap cache

[l.stach@pengutronix.de (Lucas Stach)]

Am Donnerstag, den 23.03.2017, 02:53 +0800 schrieb Dong Aisheng:
> Hi Lucas,
> 
> Thanks for the review.
> 
> On Mon, Mar 20, 2017 at 10:38:21AM +0100, Lucas Stach wrote:
> > Am Montag, den 20.03.2017, 14:15 +0800 schrieb Dong Aisheng:
> > > Without providing the proper reg_defaults, the regmap registers first
> > > read out may be always 0 if enabling cache, which results in the
> > > following issue we met.
> > > e.g. During driver probe in imx6_pm_domain_power_on():
> > > regmap_read(pd->regmap, pd->reg_offs + GPC_PGC_PUPSCR_OFFS, &val);
> > > The PGC_PUPSCR register val is always 0 but it's actually 0xf01 in HW.
> > > 
> > > Since GPC registers are tightly related to CPU bring up and may be
> > > changed in bootloader, we don't want to provide defaults.
> > > And the cache really does not save too much for GPC module.
> > > 
> > > Therefore, simply disable cache to fix the issue and make life easy.
> > 
> > While I agree that not using the cache may be the right thing to do
> > here, bypassing the cache by not providing the volatile function is only
> > half the fix.
> > 
> 
> Removing volatile function actually is only due to it becomes meaningless
> after disable cache, not used to bypass or fix the cache issue.
> 
> > Please also set the cache type to REGCACHE_NONE, to make it clear that
> > the cache isn't used.
> > 
> 
> I believe all guys normally may know the regmap cache is disabled by default
> if without specifying cache_type, this way is also commonly used in kernel.
> So i just simply remove it.
> Another bonus is it fully hides the cache bits from drive user.
> No one needs to know it if not use.
> 
> Anyway, if you insist on it, i could explicitly claim the cache type to
> REGCACHE_NONE in V2.

Um, no thanks. I claim lack of coffee for my first review. This patch is

Reviewed-by: Lucas Stach <l.stach@pengutronix.de>

> > 
> > > Cc: Lucas Stach <l.stach@pengutronix.de>
> > > Cc: Shawn Guo <shawnguo@kernel.org>
> > > Fixes: 721cabf6c660 ("soc: imx: move PGC handling to a new GPC driver")
> > > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> > > ---
> > >  drivers/soc/imx/gpc.c | 10 ----------
> > >  1 file changed, 10 deletions(-)
> > > 
> > > diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> > > index c9bfdfd..7e6a672 100644
> > > --- a/drivers/soc/imx/gpc.c
> > > +++ b/drivers/soc/imx/gpc.c
> > > @@ -289,22 +289,12 @@ static bool imx_gpc_readable_reg(struct device *dev, unsigned int reg)
> > >  	return (reg % 4 == 0) && (reg <= 0x2ac);
> > >  }
> > >  
> > > -static bool imx_gpc_volatile_reg(struct device *dev, unsigned int reg)
> > > -{
> > > -	if (reg == GPC_CNTR)
> > > -		return true;
> > > -
> > > -	return false;
> > > -}
> > > -
> > >  static const struct regmap_config imx_gpc_regmap_config = {
> > > -	.cache_type = REGCACHE_FLAT,
> > >  	.reg_bits = 32,
> > >  	.val_bits = 32,
> > >  	.reg_stride = 4,
> > >  
> > >  	.readable_reg = imx_gpc_readable_reg,
> > > -	.volatile_reg = imx_gpc_volatile_reg,
> > >  
> > >  	.max_register = 0x2ac,
> > >  };
> > 
> >