diff mbox series

[v5,1/3] i2c: aspeed: Add slave_enable() to toggle slave mode

Message ID 20210714033833.11640-2-quan@os.amperecomputing.com
State New
Headers show
Series Add SSIF BMC driver | expand

Commit Message

Quan Nguyen July 14, 2021, 3:38 a.m. UTC
Slave needs time to prepare the response data before Master could
enquiry via read transaction. However, there is no mechanism for
i2c-aspeed Slave to notify Master that it needs more time to process
and this make Master side to time out when trying to get the response.

This commit introduces the slave_enable() callback in struct
i2c_algorithm for Slave to temporary stop the Slave mode while working
on the response and re-enable the Slave when response data ready.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
---
v5:
  + None

v4:
  + First introduced follow Ryan's suggestion               [Ryan]
  + Fix recursive spinlock issue in v3 (aspeed_set_slave_busy())
  and apply in this patch                                 [Graeme]

 drivers/i2c/busses/i2c-aspeed.c | 20 ++++++++++++++++++++
 include/linux/i2c.h             |  2 ++
 2 files changed, 22 insertions(+)

Comments

Wolfram Sang Aug. 12, 2021, 7:39 a.m. UTC | #1
Hi all,

On Wed, Jul 14, 2021 at 10:38:31AM +0700, Quan Nguyen wrote:
> Slave needs time to prepare the response data before Master could
> enquiry via read transaction. However, there is no mechanism for
> i2c-aspeed Slave to notify Master that it needs more time to process
> and this make Master side to time out when trying to get the response.
> 
> This commit introduces the slave_enable() callback in struct
> i2c_algorithm for Slave to temporary stop the Slave mode while working
> on the response and re-enable the Slave when response data ready.

Sorry that I couldn't chime in earlier, but NAK!

>  include/linux/i2c.h             |  2 ++

@Corey: Please do not change this file without my ACK. It is not a
trivial change but an API extenstion and that should really be acked by
the subsystem maintainer, in this case me. I was really surprised to see
this in linux-next already.

@all: Plus, I neither like the API (because it doesn't look generic to
me but mostly handling one issue needed here) nor do I fully understand
the use case. Normally, when a read is requested and the backend needs
time to deliver the data, the hardware should stretch the SCL clock
until some data register is finally written to. If it doesn't do it for
whatever reason, this is a quirky hardware in my book and needs handling
in the driver only. So, what is special with this HW? Can't we solve it
differently?

All the best,

   Wolfram
Corey Minyard Aug. 12, 2021, 1:36 p.m. UTC | #2
On Thu, Aug 12, 2021 at 09:39:43AM +0200, Wolfram Sang wrote:
> Hi all,
> 
> On Wed, Jul 14, 2021 at 10:38:31AM +0700, Quan Nguyen wrote:
> > Slave needs time to prepare the response data before Master could
> > enquiry via read transaction. However, there is no mechanism for
> > i2c-aspeed Slave to notify Master that it needs more time to process
> > and this make Master side to time out when trying to get the response.
> > 
> > This commit introduces the slave_enable() callback in struct
> > i2c_algorithm for Slave to temporary stop the Slave mode while working
> > on the response and re-enable the Slave when response data ready.
> 
> Sorry that I couldn't chime in earlier, but NAK!
> 
> >  include/linux/i2c.h             |  2 ++
> 
> @Corey: Please do not change this file without my ACK. It is not a
> trivial change but an API extenstion and that should really be acked by
> the subsystem maintainer, in this case me. I was really surprised to see
> this in linux-next already.

I am sorry, I'll pull it out.

-corey

> 
> @all: Plus, I neither like the API (because it doesn't look generic to
> me but mostly handling one issue needed here) nor do I fully understand
> the use case. Normally, when a read is requested and the backend needs
> time to deliver the data, the hardware should stretch the SCL clock
> until some data register is finally written to. If it doesn't do it for
> whatever reason, this is a quirky hardware in my book and needs handling
> in the driver only. So, what is special with this HW? Can't we solve it
> differently?
> 
> All the best,
> 
>    Wolfram
> 




> _______________________________________________
> Openipmi-developer mailing list
> Openipmi-developer@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/openipmi-developer
diff mbox series

Patch

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 67e8b97c0c95..a6a19dc8a501 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -785,6 +785,25 @@  static int aspeed_i2c_unreg_slave(struct i2c_client *client)
 
 	return 0;
 }
+
+static int aspeed_i2c_slave_enable(struct i2c_client *client, bool enable)
+{
+	struct aspeed_i2c_bus *bus = i2c_get_adapdata(client->adapter);
+	u32 func_ctrl_reg_val;
+
+	if (!bus->slave)
+		return -EINVAL;
+
+	/* Toggle slave mode. */
+	func_ctrl_reg_val = readl(bus->base + ASPEED_I2C_FUN_CTRL_REG);
+	if (enable)
+		func_ctrl_reg_val |= ASPEED_I2CD_SLAVE_EN;
+	else
+		func_ctrl_reg_val &= ~ASPEED_I2CD_SLAVE_EN;
+	writel(func_ctrl_reg_val, bus->base + ASPEED_I2C_FUN_CTRL_REG);
+
+	return 0;
+}
 #endif /* CONFIG_I2C_SLAVE */
 
 static const struct i2c_algorithm aspeed_i2c_algo = {
@@ -793,6 +812,7 @@  static const struct i2c_algorithm aspeed_i2c_algo = {
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 	.reg_slave	= aspeed_i2c_reg_slave,
 	.unreg_slave	= aspeed_i2c_unreg_slave,
+	.slave_enable	= aspeed_i2c_slave_enable,
 #endif /* CONFIG_I2C_SLAVE */
 };
 
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 3eb60a2e9e61..8c1765aa7e3f 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -520,6 +520,7 @@  i2c_register_board_info(int busnum, struct i2c_board_info const *info,
  *   from the ``I2C_FUNC_*`` flags.
  * @reg_slave: Register given client to I2C slave mode of this adapter
  * @unreg_slave: Unregister given client from I2C slave mode of this adapter
+ * @slave_enable: Toggle enable slave mode for given client of this adapter
  *
  * The following structs are for those who like to implement new bus drivers:
  * i2c_algorithm is the interface to a class of hardware solutions which can
@@ -557,6 +558,7 @@  struct i2c_algorithm {
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 	int (*reg_slave)(struct i2c_client *client);
 	int (*unreg_slave)(struct i2c_client *client);
+	int (*slave_enable)(struct i2c_client *client, bool enable);
 #endif
 };