Re: [V7, 2/2] media: i2c: dw9768: Add DW9768 VCM driver

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Dongchun Zhu <dongchun.zhu@mediatek.com>
Cc: linus.walleij@linaro.org, bgolaszewski@baylibre.com,
	mchehab@kernel.org, robh+dt@kernel.org, mark.rutland@arm.com,
	sakari.ailus@linux.intel.com, drinkcat@chromium.org,
	tfiga@chromium.org, matthias.bgg@gmail.com, bingbu.cao@intel.com,
	srv_heupstream@mediatek.com, linux-mediatek@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org, sj.huang@mediatek.com,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	louis.kuo@mediatek.com, shengnan.wang@mediatek.com
Subject: Re: [V7, 2/2] media: i2c: dw9768: Add DW9768 VCM driver
Date: Mon, 8 Jun 2020 16:27:20 +0300	[thread overview]
Message-ID: <20200608132720.GS2428291@smile.fi.intel.com> (raw)
In-Reply-To: <1591424358.8804.599.camel@mhfsdcap03>

On Sat, Jun 06, 2020 at 02:19:18PM +0800, Dongchun Zhu wrote:
> On Fri, 2020-06-05 at 15:46 +0300, Andy Shevchenko wrote:
> > On Fri, Jun 05, 2020 at 06:54:12PM +0800, Dongchun Zhu wrote:

...

> > > +	depends on I2C && VIDEO_V4L2
> > 
> > No compile test?
> > 
> 
> Sorry?
> Kconfig here is based on the current media tree master branch.
> It is also what the other similar drivers from Dongwoon do. 

COMPILE_TEST.
I dunno if it's established or not practice in media subsystem.

...

> > > +/*
> > > + * DW9768 requires waiting time (delay time) of t_OPR after power-up,
> > > + * or in the case of PD reset taking place.
> > > + */
> > > +#define DW9768_T_OPR_US				1000
> > > +#define DW9768_Tvib_MS_BASE10			(64 - 1)
> > > +#define DW9768_AAC_MODE_DEFAULT			2
> > 
> > > +#define DW9768_AAC_TIME_DEFAULT			0x20
> > 
> > Hex? Why not decimal?
> > 
> 
> There is one optional property 'dongwoon,aac-timing' defined in DT.
> I don't know whether you have noticed that.
> 
> 'DW9768_AAC_TIME_DEFAULT' is the value set to AACT[5:0] register.
> I thought the Hex unit should be proper as it is directly written to the
> Hex register.

I see. I would rather put it like (BIT(6) / 2) to show explicitly that we
choose half of the resolution.

...

> > > +	val = ((unsigned char)ret & ~mask) | (val & mask);
> > 
> > This cast is weird.
> > 
> 
> Thanks for the review, but this cast is using classical pattern from
> your suggestion on OV02A10 v5:
> https://patchwork.linuxtv.org/patch/59788/
> 
> So I wonder whether it is still required to be refined currently.
> Or what would it be supposed to do for the cast?

Okay, does it produce a warning w/o cast?
If yes, replace it at least to be the same type as mask and val.

...

> > > +	for ( ; val >= 0; val -= DW9768_MOVE_STEPS) {
> > > +		ret = dw9768_set_dac(dw9768, val);
> > > +		if (ret) {
> > > +			dev_err(&client->dev, "I2C write fail: %d", ret);
> > > +			return ret;
> > > +		}
> > > +		usleep_range(move_delay_us, move_delay_us + 1000);
> > > +	}
> > 
> > 
> > It will look more naturally in the multiplier kind of value.
> > 
> > 	unsigned int steps = DIV_ROUND_UP(...);
> > 
> > 	while (steps--) {
> > 		...(..., steps * ..._MOVE_STEPS);
> > 		...
> > 	}
> > 
> > but double check arithmetics.
> 
> The current coding style is actually updated with reference to your
> previous comments on DW9768 v3:
> https://patchwork.linuxtv.org/patch/61856/

I understand, but can you consider to go further and see if the proposal works?

-- 
With Best Regards,
Andy Shevchenko