Re: [PATCH v4 1/6] media: i2c: ov5640: Remain in power down for DVP mode unless streaming

From: Hugues FRUCHET <hugues.fruchet@st.com>
To: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Jacopo Mondi <jacopo+renesas@jmondi.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Steve Longerbeam <slongerbeam@gmail.com>,
	Paul <paul.kocialkowski@bootlin.com>
Cc: "linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>,
	"Biju Das" <biju.das.jz@bp.renesas.com>,
	Prabhakar <prabhakar.csengg@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>
Subject: Re: [PATCH v4 1/6] media: i2c: ov5640: Remain in power down for DVP mode unless streaming
Date: Wed, 9 Sep 2020 16:16:01 +0000	[thread overview]
Message-ID: <8b5d4928-2921-b876-7d1e-04bb42eff4fa@st.com> (raw)
In-Reply-To: <20200904201835.5958-2-prabhakar.mahadev-lad.rj@bp.renesas.com>

Hi Prabhakar,

As discussed separately I would prefer to better understand issue before 
going to this patch.
Nevertheless I have some remarks in code in case we'll need it at the end.

On 9/4/20 10:18 PM, Lad Prabhakar wrote:
> Keep the sensor in software power down mode and wake up only in
> ov5640_set_stream_dvp() callback.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
> Tested-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>   drivers/media/i2c/ov5640.c | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> index 2fe4a7ac0592..880fde73a030 100644
> --- a/drivers/media/i2c/ov5640.c
> +++ b/drivers/media/i2c/ov5640.c
> @@ -34,6 +34,8 @@
>   #define OV5640_REG_SYS_RESET02		0x3002
>   #define OV5640_REG_SYS_CLOCK_ENABLE02	0x3006
>   #define OV5640_REG_SYS_CTRL0		0x3008
> +#define OV5640_REG_SYS_CTRL0_SW_PWDN	0x42
> +#define OV5640_REG_SYS_CTRL0_SW_PWUP	0x02

For the time being this section was only referring to registers 
addresses and bit details was explained into a comment right before 
affectation, see OV5640_REG_IO_MIPI_CTRL00 for example.

>   #define OV5640_REG_CHIP_ID		0x300a
>   #define OV5640_REG_IO_MIPI_CTRL00	0x300e
>   #define OV5640_REG_PAD_OUTPUT_ENABLE01	0x3017
> @@ -1120,6 +1122,12 @@ static int ov5640_load_regs(struct ov5640_dev *sensor,
>   		val = regs->val;
>   		mask = regs->mask;
>   
> +		/* remain in power down mode for DVP */
> +		if (regs->reg_addr == OV5640_REG_SYS_CTRL0 &&
> +		    val == OV5640_REG_SYS_CTRL0_SW_PWUP &&
> +		    sensor->ep.bus_type != V4L2_MBUS_CSI2_DPHY)
> +			continue;
> +

I understand that more or less register OV5640_REG_SYS_CTRL0 (0x3008) 
has been partially removed from big init sequence: for power-up part, 
but power-dwn remains at very beginning of sequence.
We should completely remove 0x3008 from init sequence, including 
power-dwn, and introduce a new function ov5640_sw_powerdown(on/off) that 
should be called at the right place instead.

>   		if (mask)
>   			ret = ov5640_mod_reg(sensor, reg_addr, mask, val);
>   		else
> @@ -1297,9 +1305,14 @@ static int ov5640_set_stream_dvp(struct ov5640_dev *sensor, bool on)
>   	 * PAD OUTPUT ENABLE 02
>   	 * - [7:2]:	D[5:0] output enable
>   	 */
> -	return ov5640_write_reg(sensor,
> -				OV5640_REG_PAD_OUTPUT_ENABLE02,
> -				on ? 0xfc : 0);
> +	ret = ov5640_write_reg(sensor, OV5640_REG_PAD_OUTPUT_ENABLE02,
> +			       on ? 0xfc : 0);
> +	if (ret)
> +		return ret;
> +
> +	return ov5640_write_reg(sensor, OV5640_REG_SYS_CTRL0, on ?
> +				OV5640_REG_SYS_CTRL0_SW_PWUP :
> +				OV5640_REG_SYS_CTRL0_SW_PWDN);
>   }
>   
>   static int ov5640_set_stream_mipi(struct ov5640_dev *sensor, bool on)
> 

BR,
Hugues.