From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 096995BFB5; Mon, 18 Dec 2023 18:04:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="L8jJ5DBx" Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 818F856D; Mon, 18 Dec 2023 19:04:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1702922643; bh=2G5GZYZ2ILPD00J2WA5+Mik9rZH8b2nzLo3y3FT055E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=L8jJ5DBxTYu1RrOWvq64ZXjcjviewadYvLSY5LBIzw6i3ooldGacfu0TnacCxdEP5 RoZ03bKl0ddPFuUEr0cgyRLcRwH8RNQqd2dmmUMGT7KQlDf2V2ZNnS4uhIXhemZhSt qtYM/xblp9t2+Blpood121l7II8ydibZbDVz/RC0= Date: Mon, 18 Dec 2023 20:04:59 +0200 From: Laurent Pinchart To: Mikhail Rudenko Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Sakari Ailus , Jacopo Mondi , Christophe JAILLET , Dave Stevenson , Mauro Carvalho Chehab Subject: Re: [PATCH 12/19] media: i2c: ov4689: Implement digital gain control Message-ID: <20231218180459.GS5290@pendragon.ideasonboard.com> References: <20231211175023.1680247-1-mike.rudenko@gmail.com> <20231211175023.1680247-13-mike.rudenko@gmail.com> <20231211221533.GK27535@pendragon.ideasonboard.com> <875y13pnn6.fsf@gmail.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <875y13pnn6.fsf@gmail.com> Hi Mikhail, On Tue, Dec 12, 2023 at 03:52:48PM +0300, Mikhail Rudenko wrote: > On 2023-12-12 at 00:15 +02, Laurent Pinchart wrote: > > On Mon, Dec 11, 2023 at 08:50:15PM +0300, Mikhail Rudenko wrote: > >> The OV4689 sensor supports digital gain up to 16x. Implement > >> corresponding control in the driver. Default digital gain value is not > >> modified by this patch. > >> > >> Signed-off-by: Mikhail Rudenko > >> --- > >> drivers/media/i2c/ov4689.c | 16 ++++++++++++++-- > >> 1 file changed, 14 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/media/i2c/ov4689.c b/drivers/media/i2c/ov4689.c > >> index 62aeae43d749..ed0ce1b9e55b 100644 > >> --- a/drivers/media/i2c/ov4689.c > >> +++ b/drivers/media/i2c/ov4689.c > >> @@ -35,6 +35,12 @@ > >> #define OV4689_GAIN_STEP 1 > >> #define OV4689_GAIN_DEFAULT 0x80 > >> > >> +#define OV4689_REG_DIG_GAIN CCI_REG16(0x352A) > > > > Lowercase for hex constatns please. > > Ah, missed it somehow. Is this convention kernel-wide or media specific? > I think checkpatch could have detetected this.. It's media-wide :-) Lower-case hex constants are the majority through the kernel, but there's no tree-wide ban on upper-case. > >> +#define OV4689_DIG_GAIN_MIN 1 > >> +#define OV4689_DIG_GAIN_MAX 0x7fff > >> +#define OV4689_DIG_GAIN_STEP 1 > >> +#define OV4689_DIG_GAIN_DEFAULT 0x800 > >> + > >> #define OV4689_REG_TEST_PATTERN CCI_REG8(0x5040) > >> #define OV4689_TEST_PATTERN_ENABLE 0x80 > >> #define OV4689_TEST_PATTERN_DISABLE 0x0 > >> @@ -131,7 +137,6 @@ static const struct cci_reg_sequence ov4689_2688x1520_regs[] = { > >> > >> /* AEC PK */ > >> {CCI_REG8(0x3503), 0x04}, /* AEC_MANUAL gain_input_as_sensor_gain_format = 1 */ > >> - {CCI_REG8(0x352a), 0x08}, /* DIG_GAIN_FRAC_LONG dig_gain_long[14:8] = 0x08 (2x) */ > > > > Is the default value really x2 ? That's not very nice :-S > > > > It would be much nicer if the default value of the control mapped to x1, > > otherwise it's impossible for userspace to interpret the scale of the > > digital gain value in a generic way. I suppose that could break existing > > applications though, which isn't great. > > The datasheet does not explicitly say how register values are mapped to > the actual gain. 0x8 comes from the original register tables, and can > also be found in a few other drivers for this sensor, although they do > not implement digital gain control. > > OTOH, the power-on value of this register, and default value as found in > the datasheet, is 0x4. This was the motivation behind that "(2x)" > annotation. I wonder if the chip has a TPG that would be located before the digital gain. It would be a nice way to test the digital gain scale. > So, I'm afraid that we cannot interpret the absolute scale of the > digital gain in any case, unless we have more documentation. I tend to > keep the default value of 0x8 for the reasons of not (possibly) breaking > userspace. > > > Out of curiosity, can you tell what SoC(s) you're using this sensor with > > ? > > It's Rockchip 3399. I run most of my tests with AGC and AWB off, to be > sure they do not hide some important details. > > >> > >> /* ADC and analog control*/ > >> {CCI_REG8(0x3603), 0x40}, > >> @@ -622,6 +627,9 @@ static int ov4689_set_ctrl(struct v4l2_ctrl *ctrl) > >> OV4689_TIMING_FLIP_MASK, > >> val ? 0 : OV4689_TIMING_FLIP_BOTH, &ret); > >> break; > >> + case V4L2_CID_DIGITAL_GAIN: > >> + cci_write(regmap, OV4689_REG_DIG_GAIN, val, &ret); > >> + break; > >> default: > >> dev_warn(dev, "%s Unhandled id:0x%x, val:0x%x\n", > >> __func__, ctrl->id, val); > >> @@ -650,7 +658,7 @@ static int ov4689_initialize_controls(struct ov4689 *ov4689) > >> > >> handler = &ov4689->ctrl_handler; > >> mode = ov4689->cur_mode; > >> - ret = v4l2_ctrl_handler_init(handler, 13); > >> + ret = v4l2_ctrl_handler_init(handler, 14); > >> if (ret) > >> return ret; > >> > >> @@ -693,6 +701,10 @@ static int ov4689_initialize_controls(struct ov4689 *ov4689) > >> v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_VFLIP, 0, 1, 1, 0); > >> v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_HFLIP, 0, 1, 1, 0); > >> > >> + v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_DIGITAL_GAIN, > >> + OV4689_DIG_GAIN_MIN, OV4689_DIG_GAIN_MAX, > >> + OV4689_DIG_GAIN_STEP, OV4689_DIG_GAIN_DEFAULT); > >> + > >> if (handler->error) { > >> ret = handler->error; > >> dev_err(ov4689->dev, "Failed to init controls(%d)\n", ret); -- Regards, Laurent Pinchart