[PATCH v3 6/6] i2c: npcm: Enable slave in eob interrupt

[PATCH v3 6/6] i2c: npcm: Enable slave in eob interrupt

[Tyrone Ting]

From: Charles Boyer <Charles.Boyer@fii-usa.com>

Nuvoton slave enable was in user space API call master_xfer, so it is
subject to delays from the OS scheduler. If the BMC is not enabled for
slave mode in time for master to send response, then it will NAK the
address match. Then the PLDM request timeout occurs.

If the slave enable is moved to the EOB interrupt service routine, then
the BMC can be ready in slave mode by the time it needs to receive a
response.

Signed-off-by: Charles Boyer <Charles.Boyer@fii-usa.com>
Signed-off-by: Vivekanand Veeracholan <vveerach@google.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 03de1353ad6e..bb4586563c0c 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -1781,6 +1781,12 @@ static int npcm_i2c_int_master_handler(struct npcm_i2c *bus)
 	    (FIELD_GET(NPCM_I2CCST3_EO_BUSY,
 		       ioread8(bus->reg + NPCM_I2CCST3)))) {
 		npcm_i2c_irq_handle_eob(bus);
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+		/* reenable slave if it was enabled */
+		if (bus->slave)
+			iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
+				 bus->reg + NPCM_I2CADDR1);
+#endif
 		return 0;
 	}
 
-- 
2.34.1

Re: [PATCH v3 6/6] i2c: npcm: Enable slave in eob interrupt

[Andy Shevchenko]

On Fri, Sep 13, 2024 at 06:15:32PM +0800, Tyrone Ting wrote:
> From: Charles Boyer <Charles.Boyer@fii-usa.com>
> 
> Nuvoton slave enable was in user space API call master_xfer, so it is
> subject to delays from the OS scheduler. If the BMC is not enabled for
> slave mode in time for master to send response, then it will NAK the
> address match. Then the PLDM request timeout occurs.
> 
> If the slave enable is moved to the EOB interrupt service routine, then
> the BMC can be ready in slave mode by the time it needs to receive a
> response.

Fixes tag?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 6/6] i2c: npcm: Enable slave in eob interrupt

[Tyrone Ting]

Hi Andy:

Thank you for your feedback.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年9月13日 週五 下午6:29寫道：
>
> On Fri, Sep 13, 2024 at 06:15:32PM +0800, Tyrone Ting wrote:
> > From: Charles Boyer <Charles.Boyer@fii-usa.com>
> >
> > Nuvoton slave enable was in user space API call master_xfer, so it is
> > subject to delays from the OS scheduler. If the BMC is not enabled for
> > slave mode in time for master to send response, then it will NAK the
> > address match. Then the PLDM request timeout occurs.
> >
> > If the slave enable is moved to the EOB interrupt service routine, then
> > the BMC can be ready in slave mode by the time it needs to receive a
> > response.
>
> Fixes tag?
>
The patch is to reduce the time for the i2c module to behave as a target.
IOW, the i2c module target function will be ready earlier than it was.
So I remove the Fixes tag.

> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you.

Regards,
Tyrone