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

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Message-ID: <67d34216-e98b-43d9-afd1-2e73ffb71968@molgen.mpg.de>
Date: Mon, 21 Oct 2024 09:01:14 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Tyrone Ting <warp5tw@...il.com>
Cc: avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com,
 venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com,
 andi.shyti@...nel.org, 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

Dear Tyrone,


Thank you for your patch.

Am 21.10.24 um 08:27 schrieb Tyrone Ting:
> From: Tyrone Ting <kfting@...oton.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().

Thank you for the description. For the summary/title it’d be great, if 
you were more specific. For example:

i2c: npcm: Assign client address earlier for `i2c_recover_bus()`

It’d be great if you noted the commit, your patch fixes, so it’s clear 
since when the problem has been present.

> Signed-off-by: Tyrone Ting <kfting@...oton.com>
> Reviewed-by: Tali Perry <tali.perry1@...il.com>
> ---
>   drivers/i2c/busses/i2c-npcm7xx.c | 20 +++++++++++++++++++-
>   1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> index c96a25d37c14..a9a9b21f1f0b 100644
> --- a/drivers/i2c/busses/i2c-npcm7xx.c
> +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> @@ -2155,6 +2155,16 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>   
>   	} while (time_is_after_jiffies(time_left) && bus_busy);
>   
> +	/*
> +	 * 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().
> +	 */
> +	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;
>   	bus->msgs = msgs;
>   	bus->msgs_num = num;
>   	bus->cmd_err = 0;


Kind regards,

Paul