linux-kernel - Re: [PATCH v3 07/15] media: i2c: ds90ub960: Add support for I2C_RX

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Message-ID: <d72utbt36uhutdlzl5a6vkjl7mxl2cfgfo6ax6fuvkpit2u3i4@eov4fsavtxw4>
Date: Thu, 5 Dec 2024 17:30:13 +0530
From: Jai Luthra <jai.luthra@...asonboard.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Hans Verkuil <hverkuil-cisco@...all.nl>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/15] media: i2c: ds90ub960: Add support for I2C_RX_ID

Hi Tomi,

On Dec 05, 2024 at 10:31:42 +0200, Andy Shevchenko wrote:
> On Wed, Dec 04, 2024 at 01:05:21PM +0200, Tomi Valkeinen wrote:
> > Normally the driver accesses both the RX and the TX port registers via a
> > paging mechanism: one register is used to select the page (i.e. the
> > port), which dictates the port used when accessing the port specific
> > registers.
> > 
> > The downside to this is that while debugging it's almost impossible to
> > access the port specific registers from the userspace, as the driver can
> > change the page at any moment.
> > 
> > The hardware supports another access mechanism: using the I2C_RX_ID
> > registers (one for each RX port), i2c addresses can be chosen which,
> > when accessed, will always use the specific port's registers, skipping
> > the paging mechanism.
> > 
> > The support is only for the RX port, but it has proven very handy while
> > debugging and testing. So let's add the code for this, but hide it
> > behind a disabled define.
> 
> ...
> 
> >  #define MHZ(v) ((u32)((v) * 1000000U))
> 
> Missed HZ_PER_MHZ from previous patch?
> 
> ...
> 
> > +#ifdef UB960_DEBUG_I2C_RX_ID
> > +	for (unsigned int i = 0; i < 4; i++)
> 
> Should it use _MAX_RX_NPORTS instead of 4?
> 

Instead of hardcoded value or the macro, it is better to use 
priv->hw_data->num_rxports.

The cut-down variant of this deser only has 2 ports for example.
https://www.ti.com/lit/gpn/ds90ub954-q1

> > +		ub960_write(priv, UB960_SR_I2C_RX_ID(i),
> > +			    (UB960_DEBUG_I2C_RX_ID + i) << 1);
> > +#endif
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

-- 
Thanks,
Jai

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