Re: [PATCH v2 06/14] mmc: dw_mmc: simplify optional reset handling

[Philipp Zabel]

On Mon, 2017-03-20 at 10:22 +0100, Andrzej Hajda wrote:
> Hi Philipp,
> 
> Todays next branch does not work with exynos5433-tm2 board.
> I guess this patch causes regression. On MMC without reset controller I
> get errors:
> [    4.938222] dwmmc_exynos 15540000.mshc: platform data not available
> [    4.943268] dwmmc_exynos: probe of 15540000.mshc failed with error -22
> [    4.950184] dwmmc_exynos 15560000.mshc: platform data not available
> [    4.955962] dwmmc_exynos: probe of 15560000.mshc failed with error -22
> 
> Commenting out reset controller get and error checks 'fixes' the issue.
> 
> On 15.03.2017 12:31, Philipp Zabel wrote:
> > As of commit bb475230b8e5 ("reset: make optional functions really
> > optional"), the reset framework API calls use NULL pointers to describe
> > optional, non-present reset controls.
> > 
> > This allows to return errors from devm_reset_control_get_optional and to
> > call reset_control_(de)assert unconditionally.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > ---
> >  drivers/mmc/host/dw_mmc.c | 14 +++++---------
> >  1 file changed, 5 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index a9ac0b4573131..3d62b0a1f81cb 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -2968,10 +2968,8 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
> >  
> >  	/* find reset controller when exist */
> >  	pdata->rstc = devm_reset_control_get_optional(dev, "reset");
> > -	if (IS_ERR(pdata->rstc)) {
> > -		if (PTR_ERR(pdata->rstc) == -EPROBE_DEFER)
> > -			return ERR_PTR(-EPROBE_DEFER);
> > -	}
> > +	if (IS_ERR(pdata->rstc))
> > +		return ERR_CAST(pdata->rstc);
> 
> 
> With three lines above commented out it works.

So devm_reset_control_get_optional returns -EINVAL. Why?

The mshc@15560000 node is compatible to "samsung,exynos7-dw-mshc-smu",
so that's dw_mmc-exynos.c calling dw_mci_pltfm_register, which then
calls dw_mci_probe, passing the original platform device as
host->dev = &pdev->dev, and I expect __of_reset_control_get being called
with a valid DT node (dev->of_node).
Since id is set to "reset", of_property_match_string(node,
"reset-names", id) should then be called and return -EINVAL because the
"reset-names" property does not exist. Then __of_reset_control_get
should return NULL because optional == true.
Some of this obviously doesn't happen, where am I wrong?

regards
Philipp