Re: [PATCH v6 2/4] i2c: npcm: Modify the client address assignment

Andy Shevchenko
2024-10-11T11:00:50Z

On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
> From: Tyrone Ting <kfting@nuvoton.com>
>
> Store the client address earlier since it might get called in
> the i2c_recover_bus() logic flow at the early stage of
> npcm_i2c_master_xfer().

...

> + /*
> + * Previously, the address was stored w/o left-shift by one bit and
> + * with that shift in the following call to npcm_i2c_master_start_xmit().
> + *
> + * Since there are cases that the i2c_recover_bus() gets called at the
> + * early stage of npcm_i2c_master_xfer(), the address is stored with
> + * the shift and used in the i2c_recover_bus().
> + *
> + * The address is stored from bit 1 to bit 7 in the register for
> + * sending the i2c address later so it's left-shifted by 1 bit.
> + */

I would rephrase it a bit like

/*
* Previously, the 7-bit address was stored and being converted to
* the address of event in the following call to npcm_i2c_master_start_xmit().
*
* Since there are cases that the i2c_recover_bus() gets called at the
* early stage of npcm_i2c_master_xfer(), the address of event is stored
* and then used in the i2c_recover_bus().
*/

(E.g., the last paragraph just describes 101 about I2C 7-bit addresses usage
and may be dropped completely.)

> + bus->dest_addr = i2c_8bit_addr_from_msg(msg0);

...

> + /*
> + * Since the transfer might be a read operation, remove the I2C_M_RD flag
> + * from the bus->dest_addr for the i2c_recover_bus() call later.
> + *
> + * The i2c_recover_bus() uses the address in a write direction to recover
> + * the i2c bus if some error condition occurs.
> + */

> + if (bus->dest_addr & I2C_M_RD)

Redundant.

> + bus->dest_addr &= ~I2C_M_RD;

--
With Best Regards,
Andy Shevchenko