RE: [PATCH 1/2] media: i2c: ov5645: Move the register 0x3008 from ov5645_global_init_setting

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Wolfram Sang <wsa@kernel.org>,
	biju.das.au <biju.das.au@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	"linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>
Subject: RE: [PATCH 1/2] media: i2c: ov5645: Move the register 0x3008 from ov5645_global_init_setting
Date: Wed, 14 Feb 2024 20:57:36 +0000	[thread overview]
Message-ID: <TYCPR01MB11269D1C9578F27DE69E732B6864E2@TYCPR01MB11269.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <TYCPR01MB11269F35E38BE52CDD6628006864E2@TYCPR01MB11269.jpnprd01.prod.outlook.com>

Hi Sakari,

> -----Original Message-----
> From: Biju Das
> Sent: Wednesday, February 14, 2024 8:55 PM
> Subject: RE: [PATCH 1/2] media: i2c: ov5645: Move the register 0x3008 from
> ov5645_global_init_setting
> 
> Hi Sakari,
> 
> Thanks for the feedback.
> 
> > -----Original Message-----
> > From: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Sent: Wednesday, February 14, 2024 8:49 PM
> > To: Biju Das <biju.das.jz@bp.renesas.com>
> > Subject: Re: [PATCH 1/2] media: i2c: ov5645: Move the register 0x3008
> > from ov5645_global_init_setting
> >
> > Hi Biju,
> >
> > On Wed, Feb 14, 2024 at 08:25:16PM +0000, Biju Das wrote:
> > > Hi Wolfram,
> > >
> > > Thanks for the feedback.
> > >
> > > > -----Original Message-----
> > > > From: Wolfram Sang <wsa@kernel.org>
> > > > Sent: Wednesday, February 14, 2024 8:31 AM
> > > > Subject: Re: [PATCH 1/2] media: i2c: ov5645: Move the register
> > > > 0x3008 from ov5645_global_init_setting
> > > >
> > > > Hi Biju,
> > > >
> > > > > I think it is different here. That 1 msec is delay associated
> > > > > with applying hardware power see [1]
> > > >
> > > > Okay, ack.
> > > >
> > > > > I will restore it.
> > > >
> > > > Thanks!
> > > >
> > > > I had meanwhile another thought. What if we kind of merge the two
> > > > patches, so the outcome is basically this:
> > > >
> > > > In ov5645_set_register_array:
> > > >
> > > > 	If (settings->reg == 0x3008 && settings->val == 0x82)
> > > > 		usleep_range(1000, 2000)
> > > >
> > > > ?
> > > >
> > > > Then, we don't need to split the array and we are also future
> > > > proof if we ever need to set the reset bit again somewhere else.
> > > >
> > > > Bonus points for replacing 0x82 with a define :)
> > > >
> > > > What do you think?
> > >
> > >
> > > OK, this will do check for all other registers.
> > >
> > > But from your power down clue and checking ov5640.c Looks like there
> > > are 2 registers changes values after writing.
> > >
> > > [1] 0x3008, 0x82-->0x80
> > > [2] 0x0601, 0x02-->0x00
> > >
> > > I think [1] is soft reset based on ov5640. Since there is a gpio
> > > based hardware reset available, we can safely remove soft reset[1]
> > > and like ov5640.c, if there is no gpio for reset, then do the soft
> reset[1].
> >
> > I guess that would work. My understanding is that hard reset control
> > is mandatory for the device, so there really should be no need for
> > soft reset in the driver.
> 
> OK.
> 
> >
> > >
> > >
> > > Then add 1msec delay for power down/up(0x3008: 0x42,0x02) and 0x0601
> > > registers.
> > >
> > > With this looks like the Camera works ok @400kHz.
> > >
> > > The plans is to add a u8 variable for delay and enable delays for
> > > the above registers and add a check like below
> > >
> > > static int ov5645_set_register_array(struct ov5645 *ov5645,
> > > 				     const struct reg_value *settings,
> > > 				     unsigned int num_settings)
> > > {
> > > 	unsigned int i;
> > > 	int ret;
> > >
> > > 	for (i = 0; i < num_settings; ++i, ++settings) {
> > > 		ret = ov5645_write_reg(ov5645, settings->reg, settings->val);
> > > 		if (ret < 0)
> > > 			return ret;
> > >
> > > 		if (settings->delay_ms)
> > > 			usleep_range(1000 * settings->delay_ms, 2 * 1000 *
> > > settings->delay_ms);
> >
> > I'd prefer checking the register address in the write function instead
> > of this if you really need it. But it seems you don't.
> 
> With delays in powerup/down registers (0x3008 : 0x42,0x02) it is not
> stable.

Typo: without delays in powerup/down registers (0x3008 : 0x42,0x02) it is not
stable.

You can see 0x42 followed by 0x02 which is an indication of power down/up procedure.

Cheers,
Biju