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Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

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  Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry  to use __ffs than ffs Linus Walleij <linus.walleij@linaro.org> - 2016-04-23 11:50 +0200
    Re: [PATCH v2] pinctrl: pinctrl-single: Fix  pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs Tony Lindgren <tony@atomide.com> - 2016-04-26 18:20 +0200

#1385604 — Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

On Fri, Apr 15, 2016 at 5:22 PM, Tony Lindgren <tony@atomide.com> wrote:
> * Linus Walleij <linus.walleij@linaro.org> [160415 02:29]:
>> On Thu, Apr 14, 2016 at 6:59 AM, Keerthy <j-keerthy@ti.com> wrote:
>>
>> > pcs_parse_bits_in_pinctrl_entry uses ffs which gives bit indices
>> > ranging from 1 to MAX. This leads to a corner case where we try to request
>> > the pin number = MAX and fails.
>> >
>> > bit_pos value is being calculted using ffs. pin_num_from_lsb uses
>> > bit_pos value. pins array is populated with:
>> >
>> > pin + pin_num_from_lsb.
>> >
>> > The above is 1 more than usual bit indices as bit_pos uses ffs to compute
>> > first set bit. Hence the last of the pins array is populated with the MAX
>> > value and not MAX - 1 which causes error when we call pin_request.
>> >
>> > mask_pos is rightly calculated as ((pcs->fmask) << (bit_pos - 1))
>> > Consequently val_pos and submask are correct.
>> >
>> > Hence use __ffs which gives (ffs(x) - 1) as the first bit set.
>> >
>> > fixes: 4e7e8017a8 ("pinctrl: pinctrl-single: enhance to configure multiple pins of different modules")
>> > Signed-off-by: Keerthy <j-keerthy@ti.com>
>> > ---
>> >
>> > Changes in v2:
>> >
>> >   * Changed pcs->fshift to use __ffs instead of ffs to be consistent.
>> >
>> > Boot tesed on da850-evm and checked the pinctrl sysfs nodes.
>>
>> Patch applied for fixes with Tony's ACK.
>>
>> Should it also be tagged for stable?
>
> Probably a good idea, I can see somebody pulling hair out because
> of this in various product trees.

Ooops sorry I totally missed to add that :(

Please ask Greg to take it as a selected stable patch.

Yours,
Linus Walleij

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#1387667 — Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

* Linus Walleij <linus.walleij@linaro.org> [160423 02:46]:
> On Fri, Apr 15, 2016 at 5:22 PM, Tony Lindgren <tony@atomide.com> wrote:
> > * Linus Walleij <linus.walleij@linaro.org> [160415 02:29]:
> >> Patch applied for fixes with Tony's ACK.
> >>
> >> Should it also be tagged for stable?
> >
> > Probably a good idea, I can see somebody pulling hair out because
> > of this in various product trees.
> 
> Ooops sorry I totally missed to add that :(
> 
> Please ask Greg to take it as a selected stable patch.

Well it has the fixes tag, let's see if the stable people will
find it automatically now :) If not, Keerthy can send email
requesting adding it manually to stable trees.

Tony

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