linux-kernel - Re: [PATCH v7 2/4] i2c: npcm: Modify the client address assignment

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Message-ID: <CACD3sJbWKkBtyq-gnicASJvRnz_nGjVAyVgnreNV7RS+MLOWJw@mail.gmail.com>
Date: Fri, 25 Oct 2024 09:43:24 +0800
From: Tyrone Ting <warp5tw@...il.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com, 
	venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com, 
	andriy.shevchenko@...ux.intel.com, wsa@...nel.org, rand.sec96@...il.com, 
	wsa+renesas@...g-engineering.com, tali.perry@...oton.com, 
	Avi.Fishman@...oton.com, tomer.maimon@...oton.com, KWLIU@...oton.com, 
	JJLIU0@...oton.com, kfting@...oton.com, openbmc@...ts.ozlabs.org, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/4] i2c: npcm: Modify the client address assignment

Hi Andi:

Thank you for your comments.

Andi Shyti <andi.shyti@...nel.org> 於 2024年10月24日 週四 下午6:04寫道：
>
> Hi Tyrone,
>
> ...
>
> > +     /*
> > +      * 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().
>
> Do we care how it was done previously? I think this is not a
> useful information as the code readers will se the code the way
> it is now, not the way it was done "previously".
>

Yes, it's not a useful information anymore.

> (there is a related comment at the end)
>
> > +      * 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().
>
> I could rephrase this sentence to something like:
>
> /*
>  * Store the address early in a global position to ensure it is
>  * accessible for a potential call to i2c_recover_bus().
>  */

Understood. Thank you for your help on this.

>
> > +      */
> > +     bus->dest_addr = i2c_8bit_addr_from_msg(msg0);
> > +
> >       /*
> >        * Check the BER (bus error) state, when ber_state is true, it means that the module
> >        * detects the bus error which is caused by some factor like that the electricity
> > @@ -2165,6 +2175,15 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >        * bus is busy.
> >        */
> >       if (bus_busy || bus->ber_state) {
> > +             /*
> > +              * 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.
> > +              */
> > +             bus->dest_addr &= ~I2C_M_RD;
> > +
> >               iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
> >               npcm_i2c_reset(bus);
> >               i2c_recover_bus(adap);
> > @@ -2172,7 +2191,6 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >       }
> >
> >       npcm_i2c_init_params(bus);
> > -     bus->dest_addr = slave_addr;
>
> We can now get rid of slave_addr. It's just used in
> npcm_i2c_master_start_xmit(). Right?

Yes, slave_addr is just used as the link
https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-npcm7xx.c#L2182
suggests with this patch.

>
> Andi
>
> >       bus->msgs = msgs;
> >       bus->msgs_num = num;
> >       bus->cmd_err = 0;
> > --
> > 2.34.1
> >

Thank you.

Regards,
Tyrone