[v6] i2c: npcm: read/write operation, checkpatch

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

Posted by Tyrone Ting 1 month, 2 weeks ago

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().

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index c96a25d37c14..349492f114e7 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2155,6 +2155,19 @@ 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 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.
+	 */
+	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 +2178,16 @@ 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.
+		 */
+		if (bus->dest_addr & I2C_M_RD)
+			bus->dest_addr &= ~I2C_M_RD;
+
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
 		i2c_recover_bus(adap);
@@ -2172,7 +2195,6 @@ 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;
-- 
2.34.1

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

Posted by Andy Shevchenko 1 month, 2 weeks ago

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

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

Posted by Tyrone Ting 1 month, 2 weeks ago

Hi Andy:

Thank you for your comments.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年10月11日 週五 下午7:00寫道：
>
> 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.)
>

Understood. I'll modify the comments and remove the last paragraph.

> > +     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.
>

Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?

> > +                     bus->dest_addr &= ~I2C_M_RD;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you again.

Regards,
Tyrone

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

Posted by Andy Shevchenko 1 month, 2 weeks ago

On Fri, Oct 11, 2024 at 09:44:42PM +0800, Tyrone Ting wrote:
> > On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:

...

> > > +             if (bus->dest_addr & I2C_M_RD)
> >
> > Redundant.
> 
> Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?

Yes.

> > > +                     bus->dest_addr &= ~I2C_M_RD;

-- 
With Best Regards,
Andy Shevchenko

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

Posted by Tyrone Ting 1 month, 2 weeks ago

Hi Andy:

Thank you for your feedback.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年10月11日 週五 下午9:58寫道：
>
> On Fri, Oct 11, 2024 at 09:44:42PM +0800, Tyrone Ting wrote:
> > > On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
>
> ...
>
> > > > +             if (bus->dest_addr & I2C_M_RD)
> > >
> > > Redundant.
> >
> > Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?
>
> Yes.
>
> > > > +                     bus->dest_addr &= ~I2C_M_RD;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Have a nice day.

Regards,
Tyrone