linux-kernel - Re: [PATCH v2 2/7] i2c: npcm: correct the read/write operation procedure

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Message-ID: <cfdfldh5tuhb4r5pdpgolcr2roeewsobedet2uvmpbnqlw5yh4@c4a2szsbs2r2>
Date: Thu, 5 Sep 2024 23:29:26 +0200
From: Andi Shyti <andi.shyti@...nel.org>
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, 
	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 v2 2/7] i2c: npcm: correct the read/write operation
 procedure

Hi Tyronne,

On Fri, Aug 30, 2024 at 11:46:35AM GMT, Tyrone Ting wrote:
> Originally the driver uses the XMIT bit in SMBnST register to decide
> the upcoming i2c transaction. If XMIT bit is 1, then it will be an i2c
> write operation. If it's 0, then a read operation will be executed.
> 
> After checking the datasheet, the XMIT bit is valid when the i2c module
> is acting in a slave role. Use the software status to control the i2c
> transaction flow instead when the i2c module is acting in a master role.
> 
> Fixes: 48acf8292280 ("i2c: Remove redundant comparison in npcm_i2c_reg_slave")

Fixes needs to be used if you are fixing a bug (crash,
device malfunction, etc.). If you want to use it, please describe
the bug you are fixing. Otherwise, please, remove it.

> Signed-off-by: Tyrone Ting <kfting@...oton.com>
> ---
>  drivers/i2c/busses/i2c-npcm7xx.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> index bbcb4d6668ce..2b76dbfba438 100644
> --- a/drivers/i2c/busses/i2c-npcm7xx.c
> +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> @@ -1628,13 +1628,10 @@ static void npcm_i2c_irq_handle_sda(struct npcm_i2c *bus, u8 i2cst)
>  			npcm_i2c_wr_byte(bus, bus->dest_addr | BIT(0));
>  	/* SDA interrupt, after start\restart */
>  	} else {
> -		if (NPCM_I2CST_XMIT & i2cst) {
> -			bus->operation = I2C_WRITE_OPER;
> +		if (bus->operation == I2C_WRITE_OPER)
>  			npcm_i2c_irq_master_handler_write(bus);
> -		} else {
> -			bus->operation = I2C_READ_OPER;
> +		else if (bus->operation == I2C_READ_OPER)
>  			npcm_i2c_irq_master_handler_read(bus);

mmmhhh... you are changing the logic here and you are not
describing the logic change in the commit log.

Without looking at the details, if this is a state machine you
are breaking it.

Can anyone from the ARM/NUVOTON NPCM supporters and reviewers
take a look at this patch?

Thanks,
Andi

> -		}
>  	}
>  }
>  
> -- 
> 2.34.1
>