Re: [PATCH RFC i2c-master] i2c: microchip: pci1xxxx: Add driver for I2C host controller in multifunction endpoint of pci1xxxx switch

[<Tharunkumar.Pasumarthi@microchip.com>]

On Thu, 2022-08-25 at 17:22 +0300, Andy Shevchenko wrote:
> 
> On Thu, Aug 25, 2022 at 01:15:42PM +0000,
> Tharunkumar.Pasumarthi@microchip.com wrote:
> > On Wed, 2022-08-24 at 21:31 +0300, Andy Shevchenko wrote:
> > > On Wed, Aug 24, 2022 at 6:04 PM <Tharunkumar.Pasumarthi@microchip.com>
> > > wrote:
> > > > On Tue, 2022-08-23 at 18:05 +0300, Andy Shevchenko wrote:
> > > > > On Tue, Aug 23, 2022 at 08:26:03PM +0530, Tharun Kumar P wrote:
> 
> ...
> 
> > > > > > +#define SMB_IDLE_SCALING_100KHZ              0x03E803C9
> > > > > > +#define SMB_IDLE_SCALING_400KHZ              0x01F4009D
> > > > > > +#define SMB_IDLE_SCALING_1000KHZ     0x01F4009D
> > > > > 
> > > > > Shouldn't these magics be decimals?
> > > 
> > > This Q seems unanswered.
> > 
> > These magic numbers need not be decimals. Configuring registers with these
> > values in driver will set the time in device. However, these values do not
> > convey any meaning when represented in decimals.
> 
> Hmm... Maybe you don't see this, but I see the following:
> 
> 0x03E803C9 = 65536 (i.e. 2^16) * 1000 + 969
> 0x01F4009D = 32768 (i.e. 2^15) * 1000 + 157
> 
> Pretty much sounds like a bit 15 for standard mode and bit 16 for fast modes
> shifted by 1000 to have a room for the time in presumably nanoseconds up to 1
> us.
> 
> Please, dig up into the documentation, vendor chat, etc to get more
> information
> on these values.

Sure, I will go through the documentation. Thanks.
Also, I will modify these magic numbers to decimals.

> > > > > Ditto for the rest similar stuff.
> > > > 
> > > > There is no direct correlation between the hex value and time.
> > > > Configuring
> > > > registers with these values in driver will set the time in device.
> 
> ...
> 
> > > > > > +#define I2C_DIR_WRITE                0
> > > > > > +#define I2C_DIR_READ         1
> > > 
> > > https://elixir.bootlin.com/linux/v6.0-rc2/source/include/uapi/linux/i2c.h#L24
> > 
> > I2C_M_RD is used in driver. But the purpose of these MACROs is different.
> > I2C_DIR_WRITE is used inside both pci1xxxx_i2c_write as well as in
> > pci1xxxx_i2c_read (for sending slave address). Thus these MACROs are
> > required
> 
> OK. Name collision still stays.

I will modify MACRO names to avoid name collision.

> > > > > Namespace collision. Doesn't I²C core provide these?
> > > > 
> > > > I am unable to find any existing MACROs for WRITE and READ in I2C core.
> > > > Kindly let me know the MACROs

Thanks,
Tharun Kumar P