Date:   Fri, 26 Jun 2020 21:19:46 +0200
From:   Drew Fustini <drew@...gleboard.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Tony Lindgren <tony@...mide.com>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Daniel Mack <daniel@...que.org>
Subject: Re: [PATCH v2] pinctrl-single: fix pcs_parse_pinconf() return value

On Tue, Jun 16, 2020 at 01:59:51PM +0200, Drew Fustini wrote:
> On Tue, Jun 16, 2020 at 10:31:54AM +0200, Linus Walleij wrote:
> > On Mon, Jun 8, 2020 at 2:51 PM Drew Fustini <drew@...gleboard.org> wrote:
> > 
> > > This patch causes pcs_parse_pinconf() to return -ENOTSUPP when no
> > > pinctrl_map is added.  The current behavior is to return 0 when
> > > !PCS_HAS_PINCONF or !nconfs.  Thus pcs_parse_one_pinctrl_entry()
> > > incorrectly assumes that a map was added and sets num_maps = 2.
> > >
> > > Analysis:
> > > =========
> > > The function pcs_parse_one_pinctrl_entry() calls pcs_parse_pinconf()
> > > if PCS_HAS_PINCONF is enabled.  The function pcs_parse_pinconf()
> > > returns 0 to indicate there was no error and num_maps is then set to 2:
> > >
> > >  980 static int pcs_parse_one_pinctrl_entry(struct pcs_device *pcs,
> > >  981                                                 struct device_node *np,
> > >  982                                                 struct pinctrl_map **map,
> > >  983                                                 unsigned *num_maps,
> > >  984                                                 const char **pgnames)
> > >  985 {
> > > <snip>
> > > 1053         (*map)->type = PIN_MAP_TYPE_MUX_GROUP;
> > > 1054         (*map)->data.mux.group = np->name;
> > > 1055         (*map)->data.mux.function = np->name;
> > > 1056
> > > 1057         if (PCS_HAS_PINCONF && function) {
> > > 1058                 res = pcs_parse_pinconf(pcs, np, function, map);
> > > 1059                 if (res)
> > > 1060                         goto free_pingroups;
> > > 1061                 *num_maps = 2;
> > > 1062         } else {
> > > 1063                 *num_maps = 1;
> > > 1064         }
> > >
> > > However, pcs_parse_pinconf() will also return 0 if !PCS_HAS_PINCONF or
> > > !nconfs.  I believe these conditions should indicate that no map was
> > > added by returning -ENOTSUPP. Otherwise pcs_parse_one_pinctrl_entry()
> > > will set num_maps = 2 even though no maps were successfully added, as
> > > it does not reach "m++" on line 940:
> > >
> > >  895 static int pcs_parse_pinconf(struct pcs_device *pcs, struct device_node *np,
> > >  896                              struct pcs_function *func,
> > >  897                              struct pinctrl_map **map)
> > >  898
> > >  899 {
> > >  900         struct pinctrl_map *m = *map;
> > > <snip>
> > >  917         /* If pinconf isn't supported, don't parse properties in below. */
> > >  918         if (!PCS_HAS_PINCONF)
> > >  919                 return 0;
> > >  920
> > >  921         /* cacluate how much properties are supported in current node */
> > >  922         for (i = 0; i < ARRAY_SIZE(prop2); i++) {
> > >  923                 if (of_find_property(np, prop2[i].name, NULL))
> > >  924                         nconfs++;
> > >  925         }
> > >  926         for (i = 0; i < ARRAY_SIZE(prop4); i++) {
> > >  927                 if (of_find_property(np, prop4[i].name, NULL))
> > >  928                         nconfs++;
> > >  929         }
> > >  930         if (!nconfs)
> > >  919                 return 0;
> > >  932
> > >  933         func->conf = devm_kcalloc(pcs->dev,
> > >  934                                   nconfs, sizeof(struct pcs_conf_vals),
> > >  935                                   GFP_KERNEL);
> > >  936         if (!func->conf)
> > >  937                 return -ENOMEM;
> > >  938         func->nconfs = nconfs;
> > >  939         conf = &(func->conf[0]);
> > >  940         m++;
> > >
> > > This situtation will cause a boot failure [0] on the BeagleBone Black
> > > (AM3358) when am33xx_pinmux node in arch/arm/boot/dts/am33xx-l4.dtsi
> > > has compatible = "pinconf-single" instead of "pinctrl-single".
> > >
> > > The patch fixes this issue by returning -ENOSUPP when !PCS_HAS_PINCONF
> > > or !nconfs, so that pcs_parse_one_pinctrl_entry() will know that no
> > > map was added.
> > >
> > > Logic is also added to pcs_parse_one_pinctrl_entry() to distinguish
> > > between -ENOSUPP and other errors.  In the case of -ENOSUPP, num_maps
> > > is set to 1 as it is valid for pinconf to be enabled and a given pin
> > > group to not any pinconf properties.
> > >
> > > [0] https://lore.kernel.org/linux-omap/20200529175544.GA3766151@x1/
> > >
> > > Fixes: 9dddb4df90d1 ("pinctrl: single: support generic pinconf")
> > > Signed-off-by: Drew Fustini <drew@...gleboard.org>
> > 
> > Patch applied as non-critical (for-next) fix.
> > 
> > If there is no hurry let's merge it this way with lots of testing
> > along the way.
> > 
> > Yours,
> > Linus Walleij
> 
> Thanks, I agree more testing is a good idea.
> 
> In particular, do you have a way to followup with Haojian Zhuang within
> Linaro?
> 

Linus - do you have a way to contact Haojian Zhuan?

I found them on Freenode but they have been idle since beginning of
June.  Last email I can find on the mailing list is from March.

Tony and I would both like someone familiar with Hisilicon to comment on
this patch as it is using pinctrl-single.

Thanks,
Drew

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