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

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Date:   Fri, 22 Jun 2018 16:09:03 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     kgunda@...eaurora.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 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