linux-kernel - Re: [PATCH V3 5/7] backlight: qcom-wled: Add support for WLED4 peripheral

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Message-ID: <b40a7640af6a99bfbcb0b21025dafd38@codeaurora.org>
Date:   Mon, 25 Jun 2018 11:24:05 +0530
From:   kgunda@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     jingoohan1@...il.com, lee.jones@...aro.org,
        b.zolnierkie@...sung.com, dri-devel@...ts.freedesktop.org,
        Daniel Thompson <daniel.thompson@...aro.org>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH V3 5/7] backlight: qcom-wled: Add support for WLED4
 peripheral

On 2018-06-23 04:39, Bjorn Andersson wrote:
> On Wed 20 Jun 04:00 PDT 2018, kgunda@...eaurora.org wrote:
> 
>> On 2018-06-20 10:44, Bjorn Andersson wrote:
>> > On Tue 19 Jun 04:13 PDT 2018, Kiran Gunda wrote:
>> >
>> > > WLED4 peripheral is present on some PMICs like pmi8998 and
>> > > pm660l. It has a different register map and configurations
>> > > are also different. Add support for it.
>> > >
>> > > Signed-off-by: Kiran Gunda <kgunda@...eaurora.org>
>> > > ---
>> > >  drivers/video/backlight/qcom-wled.c | 635
>> > > ++++++++++++++++++++++++++++--------
>> > >  1 file changed, 503 insertions(+), 132 deletions(-)
>> >
>> > Split this further into a patch that does structural preparation of
>> > WLED3 support and then an addition of WLED4, the mixture makes parts of
>> > this patch almost impossible to review. Please find some comments below.
>> >
>> Sure. I will split it in the next series.
> 
> Thanks!
> 
>> > >
>> > > diff --git a/drivers/video/backlight/qcom-wled.c
>> > > b/drivers/video/backlight/qcom-wled.c
>> > [..]
>> > >
>> > >  /* WLED3 sink registers */
>> > >  #define WLED3_SINK_REG_SYNC				0x47
>> >
>> > Drop the 3 from this if it's common between the two.
>> >
>> > > -#define  WLED3_SINK_REG_SYNC_MASK			0x07
>> > > +#define  WLED3_SINK_REG_SYNC_MASK			GENMASK(2, 0)
>> > > +#define  WLED4_SINK_REG_SYNC_MASK			GENMASK(3, 0)
>> > >  #define  WLED3_SINK_REG_SYNC_LED1			BIT(0)
>> > >  #define  WLED3_SINK_REG_SYNC_LED2			BIT(1)
>> > >  #define  WLED3_SINK_REG_SYNC_LED3			BIT(2)
>> > > +#define  WLED4_SINK_REG_SYNC_LED4			BIT(3)
>> > >  #define  WLED3_SINK_REG_SYNC_ALL			0x07
>> > > +#define  WLED4_SINK_REG_SYNC_ALL			0x0f
>> > >  #define  WLED3_SINK_REG_SYNC_CLEAR			0x00
>> > >
>> > [..]
>> > > +static int wled4_set_brightness(struct wled *wled, u16 brightness)
>> >
>> > Afaict this is identical to wled3_set_brightness() with the exception
>> > that there's a minimum brightness and the base address for the
>> > brightness registers are different.
>> >
>> > I would suggest that you add a min_brightness to wled and that you
>> > figure out a way to carry the brightness base register address; and by
>> > that you squash these two functions.
>> >
>> There are four different parameters. 1) minimum brightness 2) WLED 
>> base
>> addresses
>> 3) Brightness base addresses 4) the brightness sink registers address
>> offsets also
>> different for wled 3 and wled4. (in wled3 0x40, 0x42, 0x44, where as 
>> in
>> wled4 0x57, 0x67, 0x77, 0x87).
>> 
> 
> Sorry, I must have gotten lost in the defines, I see the difference
> between the two register layouts now. If you retain the old mechanism 
> of
> doing the math openly in the function this would have been obvious.
> 
>> Irrelevant to this patch, but wled5 has some more extra registers to
>> set the brightness.  Keeping this in mind, it is better to have
>> separate functions? Otherwise we will have to use the version checks
>> in the wled_set_brightness function, if we have the common function.
> 
> Okay, so it sounds reasonable to split this out to some degree.
> 
> Regards,
> Bjorn
> --
Thanks for that !
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