Re: [PATCH V3 2/2] backlight: qcom-wled: Correct the sync_toggle sequence

[kgunda]

On 2021-03-01 15:32, Daniel Thompson wrote:
> On Mon, Mar 01, 2021 at 02:58:36PM +0530, Kiran Gunda wrote:
> > As per the current implementation, after FSC (Full Scale Current)
> > and brightness update the sync bits are transitioned from 
> > set-then-clear.
>
> This does not makes sense since there are too many verbs. Set and clear
> are both verbs so in this context: "the code will set the bit and then
> the code will clear the bit".
>
> Either:
>
> s/transitioned from set-then-clear/set-then-cleared/.
>
> Or:
>
> s/transitioned from set-then-clear/using a set-then-clear approach/.
>
> > But, the FSC and brightness sync takes place during a clear-then-set
> > transition of the sync bits.
>
> Likewise this no longer makes sense and had also become misleading.
> Two changes of state, clear and then set, do not usually result in a
> single transition.
>
> Either:
>
> s/clear-then-set/0 to 1/
>
> Alternatively, if you want to stick exclusively to the set/clear
> terminology then replace the whole quoted section with:
>
>   But, the FSC and brightness sync takes place when the sync bits are
>   set (e.g. on a rising edge).
>
>
> > So the hardware team recommends a
> > clear-then-set approach in order to guarantee such a transition
> > regardless of the previous register state.
> >
> > Signed-off-by: Kiran Gunda <kgunda@xxxxxxxxxxxxxx>
>
> With one of each of the changes proposed above:
> Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
>
>
> Daniel.
Apologies for the mistake. I have corrected and submitted the
V4 series with the "reviewed-by" tag.
> > ---
> >  drivers/video/backlight/qcom-wled.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/video/backlight/qcom-wled.c 
> > b/drivers/video/backlight/qcom-wled.c
> > index aef52b9..19f83ac 100644
> > --- a/drivers/video/backlight/qcom-wled.c
> > +++ b/drivers/video/backlight/qcom-wled.c
> > @@ -337,13 +337,13 @@ static int wled3_sync_toggle(struct wled *wled)
> >
> >  	rc = regmap_update_bits(wled->regmap,
> >  				wled->ctrl_addr + WLED3_SINK_REG_SYNC,
> > -				mask, mask);
> > +				mask, WLED3_SINK_REG_SYNC_CLEAR);
> >  	if (rc < 0)
> >  		return rc;
> >
> >  	rc = regmap_update_bits(wled->regmap,
> >  				wled->ctrl_addr + WLED3_SINK_REG_SYNC,
> > -				mask, WLED3_SINK_REG_SYNC_CLEAR);
> > +				mask, mask);
> >
> >  	return rc;
> >  }
> > @@ -353,17 +353,17 @@ static int wled5_mod_sync_toggle(struct wled 
> > *wled)
> >  	int rc;
> >  	u8 val;
> >
> > -	val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT :
> > -					     WLED5_SINK_REG_SYNC_MOD_B_BIT;
> >  	rc = regmap_update_bits(wled->regmap,
> >  				wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT,
> > -				WLED5_SINK_REG_SYNC_MASK, val);
> > +				WLED5_SINK_REG_SYNC_MASK, 0);
> >  	if (rc < 0)
> >  		return rc;
> >
> > +	val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT :
> > +					     WLED5_SINK_REG_SYNC_MOD_B_BIT;
> >  	return regmap_update_bits(wled->regmap,
> >  				  wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT,
> > -				  WLED5_SINK_REG_SYNC_MASK, 0);
> > +				  WLED5_SINK_REG_SYNC_MASK, val);
> >  }
> >
> >  static int wled_ovp_fault_status(struct wled *wled, bool *fault_set)
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
> > Forum,
> >  a Linux Foundation Collaborative Project