[PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[Eddie James]

SCL direct drive mode prevents communication with devices that
do clock stretching, so disable. The Linux driver doesn't use
this mode, and the engine can handle clock stretching.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/i2c/ast_i2c.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/ast_i2c.c b/drivers/i2c/ast_i2c.c
index 2d3fecaa14..8b24a260c0 100644
--- a/drivers/i2c/ast_i2c.c
+++ b/drivers/i2c/ast_i2c.c
@@ -76,7 +76,7 @@ static void ast_i2c_init_bus(struct udevice *dev)
 	/* Enable Master Mode. Assuming single-master */
 	writel(I2CD_MASTER_EN
 	       | I2CD_M_SDA_LOCK_EN
-	       | I2CD_MULTI_MASTER_DIS | I2CD_M_SCL_DRIVE_EN,
+	       | I2CD_MULTI_MASTER_DIS,
 	       &priv->regs->fcr);
 	/* Enable Interrupts */
 	writel(I2CD_INTR_TX_ACK
-- 
2.27.0

Re: [PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[Heiko Schocher]

Hello Eddie,

On 11.05.22 22:52, Eddie James wrote:
> SCL direct drive mode prevents communication with devices that
> do clock stretching, so disable. The Linux driver doesn't use
> this mode, and the engine can handle clock stretching.

My first thought was why not make this option configurable, as
I do not know if there is any user of this mode configuration.

But as linux does not use this option, we may can disable it.

> Signed-off-by: Eddie James <eajames@linux.ibm.com>
> ---
>  drivers/i2c/ast_i2c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Heiko Schocher <hs@denx.de>

It would be good to have here more comments from users of this driver.

bye,
Heiko
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-52   Fax: +49-8142-66989-80   Email: hs@denx.de

Re: [PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[Joel Stanley]

On Wed, 11 May 2022 at 20:52, Eddie James <eajames@linux.ibm.com> wrote:
>
> SCL direct drive mode prevents communication with devices that
> do clock stretching, so disable. The Linux driver doesn't use
> this mode, and the engine can handle clock stretching.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

I have added the aspeed team to cc for their review.

Ryan, we discovered this fix when testing the tpm i2c driver on the ast2600.

> ---
>  drivers/i2c/ast_i2c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/ast_i2c.c b/drivers/i2c/ast_i2c.c
> index 2d3fecaa14..8b24a260c0 100644
> --- a/drivers/i2c/ast_i2c.c
> +++ b/drivers/i2c/ast_i2c.c
> @@ -76,7 +76,7 @@ static void ast_i2c_init_bus(struct udevice *dev)
>         /* Enable Master Mode. Assuming single-master */
>         writel(I2CD_MASTER_EN
>                | I2CD_M_SDA_LOCK_EN
> -              | I2CD_MULTI_MASTER_DIS | I2CD_M_SCL_DRIVE_EN,
> +              | I2CD_MULTI_MASTER_DIS,
>                &priv->regs->fcr);
>         /* Enable Interrupts */
>         writel(I2CD_INTR_TX_ACK
> --
> 2.27.0
>

RE: [PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[Ryan Chen]

> -----Original Message-----
> From: Joel Stanley <joel@jms.id.au>
> Sent: Thursday, May 19, 2022 8:28 AM
> To: Eddie James <eajames@linux.ibm.com>; Ryan Chen
> <ryan_chen@aspeedtech.com>; BMC-SW <BMC-SW@aspeedtech.com>
> Cc: U-Boot Mailing List <u-boot@lists.denx.de>; hs@denx.de
> Subject: Re: [PATCH] i2c: ast_i2c: Remove SCL direct drive mode
> 
> On Wed, 11 May 2022 at 20:52, Eddie James <eajames@linux.ibm.com>
> wrote:
> >
> > SCL direct drive mode prevents communication with devices that do
> > clock stretching, so disable. The Linux driver doesn't use this mode,
> > and the engine can handle clock stretching.
> >
> > Signed-off-by: Eddie James <eajames@linux.ibm.com>
> 
> Reviewed-by: Joel Stanley <joel@jms.id.au>
> 
Reviewed-by: ryan_chen <ryan_chen@aspeedtech.com>

> I have added the aspeed team to cc for their review.
> 
> Ryan, we discovered this fix when testing the tpm i2c driver on the ast2600.
> 
Yes, it should remove. Thank for inform.
> > ---
> >  drivers/i2c/ast_i2c.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/i2c/ast_i2c.c b/drivers/i2c/ast_i2c.c index
> > 2d3fecaa14..8b24a260c0 100644
> > --- a/drivers/i2c/ast_i2c.c
> > +++ b/drivers/i2c/ast_i2c.c
> > @@ -76,7 +76,7 @@ static void ast_i2c_init_bus(struct udevice *dev)
> >         /* Enable Master Mode. Assuming single-master */
> >         writel(I2CD_MASTER_EN
> >                | I2CD_M_SDA_LOCK_EN
> > -              | I2CD_MULTI_MASTER_DIS | I2CD_M_SCL_DRIVE_EN,
> > +              | I2CD_MULTI_MASTER_DIS,
> >                &priv->regs->fcr);
> >         /* Enable Interrupts */
> >         writel(I2CD_INTR_TX_ACK
> > --
> > 2.27.0
> >

Re: [PATCH] i2c: ast_i2c: Remove SCL direct drive mode

[Heiko Schocher]

Hello Eddie,

On 11.05.22 22:52, Eddie James wrote:
> SCL direct drive mode prevents communication with devices that
> do clock stretching, so disable. The Linux driver doesn't use
> this mode, and the engine can handle clock stretching.
> 
> Signed-off-by: Eddie James <eajames@linux.ibm.com>
> ---
>  drivers/i2c/ast_i2c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied to u-boot-i2c master

Thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-52   Fax: +49-8142-66989-80   Email: hs@denx.de