[PATCH v5 0/3] Add SSIF BMC driver

[PATCH v5 0/3] Add SSIF BMC driver

[Quan Nguyen]

This series add support the SSIF BMC driver which is to perform in-band
IPMI communication with their host in management (BMC) side.

SSIF BMC driver in this series is tested with Aspeed AST2500.

v5:
  + Correct the patches order to fix the bisect issue found by
  kernel build robot

v4:
  + Fix recursive spinlock                                      [Graeme]
  + Send response with Completion code 0xFF when aborting         [Quan]
  + Fix warning with dt_binding_check                              [Rob]
  + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml                  [Quan]
  + Added bounding check on SMBus writes and the whole request     [Dan]
  + Moved buffer to end of struct ssif_bmc_ctx to avoid context
    corruption if somehow buffer is written past the end           [Dan]
  + Return -EINVAL if userspace buffer too small, dont
    silence truncate                                       [Corey, Joel]
  + Not necessary to check NONBLOCK in lock                      [Corey]
  + Enforce one user at a time                                    [Joel]
  + Reject write with invalid response length from userspace     [Corey]
  + Add state machines for better ssif bmc state handling         [Quan]
  + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
    SSIF BMC driver                                               [Quan]
  + Change compatible string "aspeed,ast2500-ssif-bmc" to
    "ampere,ssif-bmc"                                             [Quan]
  + Toggle Slave enable in i2c-aspeed to turn on/off slave mode   [Ryan]
  + Added slave_enable() to struct i2c_algorithm to control
    slave mode and to address the recursive spinlock      [Graeme, Ryan]
  + Abort current request with invalid SMBus write or
    invalid command                                               [Quan]
  + Abort all request if there is pending response                [Quan]
  + Changed validate_pec() to validate_request()                  [Quan]
  + Add unsupported_smbus_cmd() to handle unknown SMBus command   [Quan]
  + Print internal state string for ease investigating issue      [Quan]
  + Move to READY state on SLAVE_STOP event                       [Quan]
  + Change initilize_transfer() to process_smbus_cmd()            [Quan]
  + Introduce functions for each slave event                      [Quan]

v3:
  + Switched binding doc to use DT schema format [Rob]
  + Splited into generic ssif_bmc and aspeed-specific [Corey, Joel]
  + Removed redundant license info [Joel]
  + Switched to use traditional if-else [Joel]
  + Removed unused ssif_bmc_ioctl() [Joel]
  + Made handle_request()/complete_response() to return void [Joel]
  + Refactored send_ssif_bmc_response()/receive_ssif_bmc_request()
  [Corey]
  + Remove mutex [Corey]
  + Use spin_lock/unlock_irqsave/restore in callback [Corey]
  + Removed the unnecessary memset [Corey]
  + Switch to use dev_err() [Corey]
  + Combine mask/unmask two interrupts together [Corey]
  + Fixed unhandled Tx done with NAK [Quan]
  + Late ack'ed Tx done w/wo Ack irq [Quan]
  + Use aspeed-specific exported aspeed_set_slave_busy() when slave busy
  to fix the deadlock [Graeme, Philipp, Quan]
  + Clean buffer for last multipart read [Quan]
  + Handle unknown incoming command [Quan]

v2:
  + Fixed compiling error with COMPILE_TEST for arc

Quan Nguyen (3):
  i2c: aspeed: Add slave_enable() to toggle slave mode
  ipmi: ssif_bmc: Add SSIF BMC driver
  bindings: ipmi: Add binding for SSIF BMC driver

 .../devicetree/bindings/ipmi/ssif-bmc.yaml    |  38 +
 drivers/char/ipmi/Kconfig                     |  11 +
 drivers/char/ipmi/Makefile                    |   1 +
 drivers/char/ipmi/ssif_bmc.c                  | 781 ++++++++++++++++++
 drivers/char/ipmi/ssif_bmc.h                  | 106 +++
 drivers/i2c/busses/i2c-aspeed.c               |  20 +
 include/linux/i2c.h                           |   2 +
 7 files changed, 959 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
 create mode 100644 drivers/char/ipmi/ssif_bmc.c
 create mode 100644 drivers/char/ipmi/ssif_bmc.h

-- 
2.28.0

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

[Quan Nguyen]

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(+)

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
 };
 
-- 
2.28.0

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

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 1466 bytes --]

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


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Re: [Openipmi-developer] [PATCH v5 1/3] i2c: aspeed: Add slave_enable() to toggle slave mode

[Corey Minyard]

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

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

[Wolfram Sang]

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Hi,

I still wonder if we can't get the SSIF BMC driver upstream...

> @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?

... for that, it would be great if somebody could answer my questions
here :)

Happy hacking,

   Wolfram


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

[Quan Nguyen]

On 30/11/2021 02:22, Wolfram Sang wrote:
> Hi,
> 
> I still wonder if we can't get the SSIF BMC driver upstream...
> 

Thanks Wolfram to help bring this up,

This driver was tested with Aspeed ast2500 and we have tried many way to 
avoid using slave_enable() to toggle slave mode but there is no progress.
Our expectation is still to have this driver upstream'ed and I'm 
thinking about testing this driver on other HW and re-post the driver.

>> @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?
> 
> ... for that, it would be great if somebody could answer my questions
> here :)
> 

I have to admit that you are all right with the above comments. The fact 
is we still not be able to find any way to solve this differently. We 
don't own this HW and dont know what happen on this particular issue. 
The SCL clock stretching on this HW does not work as expected and the 
slave_enable() is the only solution for now. I hope if someone could 
help with the issue as well.

Best regards,
- Quan

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

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 1124 bytes --]

Hi,

> Thanks Wolfram to help bring this up,

Sure thing! It would be sad to see this work bitrot.

> This driver was tested with Aspeed ast2500 and we have tried many way to
> avoid using slave_enable() to toggle slave mode but there is no progress.

I see. I also can't help you there. I have neither experience with nor
access to this HW.

> Our expectation is still to have this driver upstream'ed and I'm thinking
> about testing this driver on other HW and re-post the driver.

That sounds like a good plan.

> I have to admit that you are all right with the above comments. The fact is
> we still not be able to find any way to solve this differently. We don't own
> this HW and dont know what happen on this particular issue. The SCL clock
> stretching on this HW does not work as expected and the slave_enable() is
> the only solution for now. I hope if someone could help with the issue as
> well.

From this distance, it looks like HW access and a logic analyzer might
be helpful in understanding the behaviour. Pity that you don't own the
HW.

Good luck nonetheless!

   Wolfram


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[PATCH v5 2/3] ipmi: ssif_bmc: Add SSIF BMC driver

[Quan Nguyen]

The SMBus system interface (SSIF) IPMI BMC driver can be used to perform
in-band IPMI communication with their host in management (BMC) side.

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

v4:
  + Send response with Completion code 0xFF when aborting         [Quan]
  + Added bounding check on SMBus writes and the whole request     [Dan]
  + Moved buffer to end of struct ssif_bmc_ctx to avoid context
    corruption if somehow buffer is written past the end           [Dan]
  + Return -EINVAL if userspace buffer too small, dont
    silence truncate                                       [Corey, Joel]
  + Not necessary to check NONBLOCK in lock                      [Corey]
  + Enforce one user at a time                                    [Joel]
  + Reject write with invalid response length from userspace     [Corey]
  + Add state machines for better ssif bmc state handling         [Quan]
  + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
    SSIF BMC driver                                               [Quan]
  + Change compatible string "aspeed,ast2500-ssif-bmc" to
    "ampere,ssif-bmc"                                             [Quan]
  + Abort current request with invalid SMBus write or
    invalid command                                               [Quan]
  + Abort all request if there is pending response                [Quan]
  + Changed validate_pec() to validate_request()                  [Quan]
  + Add unsupported_smbus_cmd() to handle unknown SMBus command   [Quan]
  + Print internal state string for ease investigating issue      [Quan]
  + Move to READY state on SLAVE_STOP event                       [Quan]
  + Change initilize_transfer() to process_smbus_cmd()            [Quan]
  + Introduce functions for each slave event                      [Quan]

v3:
  + Removed redundant license info [Joel]
  + Switched to use traditional if-else [Joel]
  + Removed unused ssif_bmc_ioctl() [Joel]
  + Made handle_request()/complete_response() to return void [Joel]
  + Refactored send_ssif_bmc_response()/receive_ssif_bmc_request()
[Corey]
  + Removed mutex [Corey]
  + Use spin_lock/unlock_irqsave/restore in callback [Corey]
  + Removed the unnecessary memset [Corey]
  + Switch to use dev_err() [Corey]

v2:
  + Fixed compiling error with COMPILE_TEST for arc

 drivers/char/ipmi/Kconfig    |  11 +
 drivers/char/ipmi/Makefile   |   1 +
 drivers/char/ipmi/ssif_bmc.c | 781 +++++++++++++++++++++++++++++++++++
 drivers/char/ipmi/ssif_bmc.h | 106 +++++
 4 files changed, 899 insertions(+)
 create mode 100644 drivers/char/ipmi/ssif_bmc.c
 create mode 100644 drivers/char/ipmi/ssif_bmc.h

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index 249b31197eea..e09a470ab2da 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -160,6 +160,17 @@ config ASPEED_BT_IPMI_BMC
 	  found on Aspeed SOCs (AST2400 and AST2500). The driver
 	  implements the BMC side of the BT interface.
 
+config SSIF_IPMI_BMC
+	tristate "SSIF IPMI BMC driver"
+	select I2C
+	select I2C_SLAVE
+	help
+	  This enables the IPMI SMBus system interface (SSIF) at the
+	  management (BMC) side.
+
+	  The driver implements the BMC side of the SMBus system
+	  interface (SSIF).
+
 config IPMB_DEVICE_INTERFACE
 	tristate 'IPMB Interface handler'
 	depends on I2C
diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
index 84f47d18007f..a93c09dad22a 100644
--- a/drivers/char/ipmi/Makefile
+++ b/drivers/char/ipmi/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
 obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o
 obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o
 obj-$(CONFIG_IPMB_DEVICE_INTERFACE) += ipmb_dev_int.o
+obj-$(CONFIG_SSIF_IPMI_BMC) += ssif_bmc.o
diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
new file mode 100644
index 000000000000..b15c05622e72
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -0,0 +1,781 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The driver for BMC side of SSIF interface
+ *
+ * Copyright (c) 2021, Ampere Computing LLC
+ *
+ */
+
+#include <linux/i2c.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+
+#include "ssif_bmc.h"
+
+static const char *state_to_string(enum ssif_state state)
+{
+	switch (state) {
+	case SSIF_READY:
+		return "SSIF_READY";
+	case SSIF_START:
+		return "SSIF_START";
+	case SSIF_SMBUS_CMD:
+		return "SSIF_SMBUS_CMD";
+	case SSIF_REQ_RECVING:
+		return "SSIF_REQ_RECVING";
+	case SSIF_RES_SENDING:
+		return "SSIF_RES_SENDING";
+	case SSIF_BAD_SMBUS:
+		return "SSIF_BAD_SMBUS";
+	default:
+		return "SSIF_STATE_UNKNOWN";
+	}
+}
+
+/* Handle SSIF message that will be sent to user */
+static ssize_t ssif_bmc_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	struct ssif_msg msg;
+	unsigned long flags;
+	ssize_t ret;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+	while (!ssif_bmc->request_available) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		ret = wait_event_interruptible(ssif_bmc->wait_queue,
+					       ssif_bmc->request_available);
+		if (ret)
+			return ret;
+		spin_lock_irqsave(&ssif_bmc->lock, flags);
+	}
+
+	if (count < min_t(ssize_t, ssif_msg_len(&ssif_bmc->request), sizeof(struct ssif_msg))) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		ret = -EINVAL;
+	} else {
+		count = min_t(ssize_t, ssif_msg_len(&ssif_bmc->request), sizeof(struct ssif_msg));
+		memcpy(&msg, &ssif_bmc->request, count);
+		ssif_bmc->request_available = false;
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+		ret = copy_to_user(buf, &msg, count);
+	}
+
+	return (ret < 0) ? ret : count;
+}
+
+/* Handle SSIF message that is written by user */
+static ssize_t ssif_bmc_write(struct file *file, const char __user *buf, size_t count,
+			      loff_t *ppos)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	struct ssif_msg msg;
+	unsigned long flags;
+	ssize_t ret;
+
+	if (count > sizeof(struct ssif_msg))
+		return -EINVAL;
+
+	ret = copy_from_user(&msg, buf, count);
+	if (ret)
+		return ret;
+
+	if (!msg.len || count < ssif_msg_len(&msg))
+		return -EINVAL;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+	while (ssif_bmc->response_in_progress) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		ret = wait_event_interruptible(ssif_bmc->wait_queue,
+					       !ssif_bmc->response_in_progress);
+		if (ret)
+			return ret;
+		spin_lock_irqsave(&ssif_bmc->lock, flags);
+	}
+
+	memcpy(&ssif_bmc->response, &msg, count);
+	ssif_bmc->is_singlepart_read = (ssif_msg_len(&msg) <= MAX_PAYLOAD_PER_TRANSACTION + 1);
+	ssif_bmc->response_in_progress = true;
+
+	if (ssif_bmc->client->adapter->algo->slave_enable)
+		ret = ssif_bmc->client->adapter->algo->slave_enable(ssif_bmc->client, true);
+
+	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+	return (ret < 0) ? ret : count;
+}
+
+static int ssif_bmc_open(struct inode *inode, struct file *file)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	int ret = 0;
+
+	spin_lock_irq(&ssif_bmc->lock);
+	if (!ssif_bmc->running)
+		ssif_bmc->running = 1;
+	else
+		ret = -EBUSY;
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return ret;
+}
+
+static unsigned int ssif_bmc_poll(struct file *file, poll_table *wait)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	unsigned int mask = 0;
+
+	poll_wait(file, &ssif_bmc->wait_queue, wait);
+
+	spin_lock_irq(&ssif_bmc->lock);
+	/* The request is available, userspace application can get the request */
+	if (ssif_bmc->request_available)
+		mask |= POLLIN;
+
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return mask;
+}
+
+static int ssif_bmc_release(struct inode *inode, struct file *file)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+
+	spin_lock_irq(&ssif_bmc->lock);
+	ssif_bmc->running = 0;
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return 0;
+}
+
+/*
+ * System calls to device interface for user apps
+ */
+static const struct file_operations ssif_bmc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ssif_bmc_open,
+	.read		= ssif_bmc_read,
+	.write		= ssif_bmc_write,
+	.release	= ssif_bmc_release,
+	.poll		= ssif_bmc_poll,
+};
+
+/* Called with ssif_bmc->lock held. */
+static void complete_response(struct ssif_bmc_ctx *ssif_bmc)
+{
+	/* Invalidate response in buffer to denote it having been sent. */
+	ssif_bmc->response.len = 0;
+	ssif_bmc->response_in_progress = false;
+	ssif_bmc->nbytes_processed = 0;
+	ssif_bmc->remain_len = 0;
+	wake_up_all(&ssif_bmc->wait_queue);
+}
+
+/* Called with ssif_bmc->lock held. */
+static void handle_request(struct ssif_bmc_ctx *ssif_bmc)
+{
+	if (ssif_bmc->client->adapter->algo->slave_enable)
+		ssif_bmc->client->adapter->algo->slave_enable(ssif_bmc->client, false);
+
+	/* Request message is available to process */
+	ssif_bmc->request_available = true;
+	/*
+	 * This is the new READ request.
+	 */
+	wake_up_all(&ssif_bmc->wait_queue);
+}
+
+static void set_multipart_response_buffer(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	u8 response_len = 0;
+	int idx = 0;
+	u8 data_len;
+
+	data_len = ssif_bmc->response.len;
+	switch (ssif_bmc->smbus_cmd) {
+	case SSIF_IPMI_MULTIPART_READ_START:
+		/*
+		 * Read Start length is 32 bytes.
+		 * Read Start transfer first 30 bytes of IPMI response
+		 * and 2 special code 0x00, 0x01.
+		 */
+		*val = MAX_PAYLOAD_PER_TRANSACTION;
+		ssif_bmc->remain_len = data_len - MAX_IPMI_DATA_PER_START_TRANSACTION;
+		ssif_bmc->block_num = 0;
+
+		ssif_bmc->response_buf[idx++] = 0x00; /* Start Flag */
+		ssif_bmc->response_buf[idx++] = 0x01; /* Start Flag */
+		ssif_bmc->response_buf[idx++] = ssif_bmc->response.netfn_lun;
+		ssif_bmc->response_buf[idx++] = ssif_bmc->response.cmd;
+		ssif_bmc->response_buf[idx++] = ssif_bmc->response.payload[0];
+
+		response_len = MAX_PAYLOAD_PER_TRANSACTION - idx;
+
+		memcpy(&ssif_bmc->response_buf[idx], &ssif_bmc->response.payload[1],
+		       response_len);
+		break;
+
+	case SSIF_IPMI_MULTIPART_READ_MIDDLE:
+		/*
+		 * IPMI READ Middle or READ End messages can carry up to 31 bytes
+		 * IPMI data plus block number byte.
+		 */
+		if (ssif_bmc->remain_len < MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION) {
+			/*
+			 * This is READ End message
+			 *  Return length is the remaining response data length
+			 *  plus block number
+			 *  Block number 0xFF is to indicate this is last message
+			 *
+			 */
+			*val = ssif_bmc->remain_len + 1;
+			ssif_bmc->block_num = 0xFF;
+			ssif_bmc->response_buf[idx++] = ssif_bmc->block_num;
+			response_len = ssif_bmc->remain_len;
+			/* Clean the buffer */
+			memset(&ssif_bmc->response_buf[idx], 0, MAX_PAYLOAD_PER_TRANSACTION - idx);
+		} else {
+			/*
+			 * This is READ Middle message
+			 *  Response length is the maximum SMBUS transfer length
+			 *  Block number byte is incremented
+			 * Return length is maximum SMBUS transfer length
+			 */
+			*val = MAX_PAYLOAD_PER_TRANSACTION;
+			ssif_bmc->remain_len -= MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
+			response_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
+			ssif_bmc->response_buf[idx++] = ssif_bmc->block_num;
+			ssif_bmc->block_num++;
+		}
+
+		memcpy(&ssif_bmc->response_buf[idx],
+		       ssif_bmc->response.payload + 1 + ssif_bmc->nbytes_processed,
+		       response_len);
+		break;
+
+	default:
+		/* Do not expect to go to this case */
+		dev_err(&ssif_bmc->client->dev,
+			"%s: Unexpected SMBus command 0x%x, aborting ...\n",
+			__func__, ssif_bmc->smbus_cmd);
+		ssif_bmc->aborting = true;
+		break;
+	}
+
+	ssif_bmc->nbytes_processed += response_len;
+}
+
+/* Process the IPMI response that will be read by master */
+static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	u8 *buf;
+	u8 pec_len, addr, len;
+	u8 pec = 0;
+
+	pec_len = ssif_bmc->pec_support ? 1 : 0;
+	/* PEC - Start Read Address */
+	addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+	pec = i2c_smbus_pec(pec, &addr, 1);
+	/* PEC - SSIF Command */
+	pec = i2c_smbus_pec(pec, &ssif_bmc->smbus_cmd, 1);
+	/* PEC - Restart Write Address */
+	addr = addr | 0x01;
+	pec = i2c_smbus_pec(pec, &addr, 1);
+
+	if (ssif_bmc->is_singlepart_read) {
+		/* Single-part Read processing */
+		buf = (u8 *)&ssif_bmc->response;
+
+		if (ssif_bmc->response.len && ssif_bmc->msg_idx < ssif_bmc->response.len) {
+			ssif_bmc->msg_idx++;
+			*val = buf[ssif_bmc->msg_idx];
+		} else if (ssif_bmc->response.len && ssif_bmc->msg_idx == ssif_bmc->response.len) {
+			ssif_bmc->msg_idx++;
+			*val = i2c_smbus_pec(pec, buf, ssif_msg_len(&ssif_bmc->response));
+		} else {
+			*val = 0;
+		}
+		/* Invalidate response buffer to denote it is sent */
+		if (ssif_bmc->msg_idx + 1 >= (ssif_msg_len(&ssif_bmc->response) + pec_len))
+			complete_response(ssif_bmc);
+	} else {
+		/* Multi-part Read processing */
+		switch (ssif_bmc->smbus_cmd) {
+		case SSIF_IPMI_MULTIPART_READ_START:
+		case SSIF_IPMI_MULTIPART_READ_MIDDLE:
+			buf = (u8 *)&ssif_bmc->response_buf;
+			*val = buf[ssif_bmc->msg_idx];
+			ssif_bmc->msg_idx++;
+			break;
+		default:
+			/* Do not expect to go to this case */
+			dev_err(&ssif_bmc->client->dev,
+				"%s: Unexpected SMBus command 0x%x, aborting ...\n",
+				__func__, ssif_bmc->smbus_cmd);
+			ssif_bmc->aborting = true;
+			break;
+		}
+
+		len = (ssif_bmc->block_num == 0xFF) ?
+		       ssif_bmc->remain_len + 1 : MAX_PAYLOAD_PER_TRANSACTION;
+		if (ssif_bmc->msg_idx == (len + 1)) {
+			pec = i2c_smbus_pec(pec, &len, 1);
+			*val = i2c_smbus_pec(pec, ssif_bmc->response_buf, len);
+		}
+		/* Invalidate response buffer to denote last response is sent */
+		if (ssif_bmc->block_num == 0xFF &&
+		    ssif_bmc->msg_idx > (ssif_bmc->remain_len + pec_len)) {
+			complete_response(ssif_bmc);
+		}
+	}
+}
+
+static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	u8 *buf = (u8 *)&ssif_bmc->request;
+
+	if (ssif_bmc->msg_idx >= sizeof(struct ssif_msg))
+		return;
+
+	switch (ssif_bmc->smbus_cmd) {
+	case SSIF_IPMI_SINGLEPART_WRITE:
+		buf[ssif_bmc->msg_idx - 1] = *val;
+		ssif_bmc->msg_idx++;
+
+		break;
+	case SSIF_IPMI_MULTIPART_WRITE_START:
+		if (ssif_bmc->msg_idx == 1)
+			ssif_bmc->request.len = 0;
+
+		fallthrough;
+	case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
+		/* The len should always be 32 */
+		if (ssif_bmc->msg_idx == 1 && *val != MAX_PAYLOAD_PER_TRANSACTION) {
+			dev_warn(&ssif_bmc->client->dev,
+				 "Warn: Invalid Multipart Write len, aborting ...");
+			ssif_bmc->aborting = true;
+		}
+
+		fallthrough;
+	case SSIF_IPMI_MULTIPART_WRITE_END:
+		/* Multi-part write, 2nd byte received is length */
+		if (ssif_bmc->msg_idx == 1) {
+			if (*val > MAX_PAYLOAD_PER_TRANSACTION) {
+				dev_warn(&ssif_bmc->client->dev,
+					 "Warn: Invalid Multipart Write End len, aborting ...");
+				ssif_bmc->aborting = true;
+			}
+
+			ssif_bmc->request.len += *val;
+			ssif_bmc->recv_len = *val;
+
+			/* request len should never exceeded 255 bytes */
+			if (ssif_bmc->request.len > 255) {
+				dev_warn(&ssif_bmc->client->dev,
+					 "Warn: Invalid request len, aborting ...");
+				ssif_bmc->aborting = true;
+			}
+
+		} else {
+			buf[ssif_bmc->msg_idx - 1 +
+			    ssif_bmc->request.len - ssif_bmc->recv_len]	= *val;
+		}
+
+		ssif_bmc->msg_idx++;
+
+		break;
+	default:
+		/* Do not expect to go to this case */
+		dev_err(&ssif_bmc->client->dev,
+			"%s: Unexpected SMBus command 0x%x, aborting ...\n",
+			__func__, ssif_bmc->smbus_cmd);
+		ssif_bmc->aborting = true;
+		break;
+	}
+}
+
+static bool validate_request(struct ssif_bmc_ctx *ssif_bmc)
+{
+	u8 rpec = 0, cpec = 0;
+	bool ret = true;
+	u8 addr, index;
+	u8 *buf;
+
+	buf = (u8 *)&ssif_bmc->request;
+	switch (ssif_bmc->smbus_cmd) {
+	case SSIF_IPMI_SINGLEPART_WRITE:
+		if ((ssif_bmc->msg_idx - 1) == ssif_msg_len(&ssif_bmc->request)) {
+			/* PEC is not included */
+			ssif_bmc->pec_support = false;
+			ret = true;
+			goto exit;
+		}
+
+		if ((ssif_bmc->msg_idx - 1) != (ssif_msg_len(&ssif_bmc->request) + 1)) {
+			dev_err(&ssif_bmc->client->dev, "Error: Unexpected length received %d\n",
+				ssif_msg_len(&ssif_bmc->request));
+			ret = false;
+			goto exit;
+		}
+
+		/* PEC is included */
+		ssif_bmc->pec_support = true;
+		rpec = buf[ssif_bmc->msg_idx - 2];
+		addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+		cpec = i2c_smbus_pec(cpec, &addr, 1);
+		cpec = i2c_smbus_pec(cpec, &ssif_bmc->smbus_cmd, 1);
+		cpec = i2c_smbus_pec(cpec, buf, ssif_msg_len(&ssif_bmc->request));
+		if (rpec != cpec) {
+			dev_err(&ssif_bmc->client->dev, "Bad PEC 0x%02x vs. 0x%02x\n", rpec, cpec);
+			ret = false;
+		}
+
+		break;
+	case SSIF_IPMI_MULTIPART_WRITE_START:
+	case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
+	case SSIF_IPMI_MULTIPART_WRITE_END:
+		index = ssif_bmc->request.len - ssif_bmc->recv_len;
+		if ((ssif_bmc->msg_idx - 1 + index) == ssif_msg_len(&ssif_bmc->request)) {
+			/* PEC is not included */
+			ssif_bmc->pec_support = false;
+			ret = true;
+			goto exit;
+		}
+
+		if ((ssif_bmc->msg_idx - 1 + index) != (ssif_msg_len(&ssif_bmc->request) + 1)) {
+			dev_err(&ssif_bmc->client->dev, "Error: Unexpected length received %d\n",
+				ssif_msg_len(&ssif_bmc->request));
+			ret = false;
+			goto exit;
+		}
+
+		/* PEC is included */
+		ssif_bmc->pec_support = true;
+		rpec = buf[ssif_bmc->msg_idx - 2 + index];
+		addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+		cpec = i2c_smbus_pec(cpec, &addr, 1);
+		cpec = i2c_smbus_pec(cpec, &ssif_bmc->smbus_cmd, 1);
+		cpec = i2c_smbus_pec(cpec, &ssif_bmc->recv_len, 1);
+		/* As SMBus specification does not allow the length
+		 * (byte count) in the Write-Block protocol to be zero.
+		 * Therefore, it is illegal to have the last Middle
+		 * transaction in the sequence carry 32-byte and have
+		 * a length of ‘0’ in the End transaction.
+		 * But some users may try to use this way and we should
+		 * prevent ssif_bmc driver broken in this case.
+		 */
+		if (ssif_bmc->recv_len != 0)
+			cpec = i2c_smbus_pec(cpec, buf + 1 + index, ssif_bmc->recv_len);
+
+		if (rpec != cpec) {
+			dev_err(&ssif_bmc->client->dev, "Bad PEC 0x%02x vs. 0x%02x\n", rpec, cpec);
+			ret = false;
+		}
+
+		break;
+	default:
+		/* Do not expect to go to this case */
+		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x, aborting ...\n",
+			__func__, ssif_bmc->smbus_cmd);
+		ret = false;
+		break;
+	}
+
+exit:
+	return ret;
+}
+
+static bool unsupported_smbus_cmd(u8 cmd)
+{
+	if (cmd == SSIF_IPMI_SINGLEPART_READ ||
+	    cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_END ||
+	    cmd == SSIF_IPMI_MULTIPART_READ_START ||
+	    cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
+		return false;
+
+	return true;
+}
+
+static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	/* SMBUS command can vary (single or multi-part) */
+	ssif_bmc->smbus_cmd = *val;
+	ssif_bmc->msg_idx++;
+
+	if (unsupported_smbus_cmd(*val)) {
+		dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus command, aborting ...");
+		ssif_bmc->aborting = true;
+	} else if (ssif_bmc->aborting &&
+		   (*val == SSIF_IPMI_SINGLEPART_WRITE ||
+		    *val == SSIF_IPMI_MULTIPART_WRITE_START)) {
+		/* New request */
+		dev_warn(&ssif_bmc->client->dev, "Warn: New request found, stop aborting ...");
+		ssif_bmc->aborting = false;
+	}
+}
+
+static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_REQ_RECVING ||
+	    ssif_bmc->state == SSIF_RES_SENDING) {
+		ssif_bmc->state = SSIF_BAD_SMBUS;
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected READ REQUESTED in state=%s, aborting ...\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->aborting = true;
+
+	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+		ssif_bmc->state = SSIF_RES_SENDING;
+	}
+
+	if (ssif_bmc->aborting || ssif_bmc->state != SSIF_RES_SENDING) {
+		/* Abort by returning the last request with 0xFF as completion code */
+		ssif_bmc->is_singlepart_read = true;
+		ssif_bmc->response.len = 0x03;
+		ssif_bmc->response.netfn_lun = ssif_bmc->request.netfn_lun | 4;
+		ssif_bmc->response.cmd = ssif_bmc->request.cmd;
+		memset(&ssif_bmc->response.payload[0], 0xFF, MAX_PAYLOAD_PER_TRANSACTION);
+	}
+
+	ssif_bmc->msg_idx = 0;
+	if (ssif_bmc->is_singlepart_read)
+		*val = ssif_bmc->response.len;
+	else
+		set_multipart_response_buffer(ssif_bmc, val);
+}
+
+static void on_read_processed_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_REQ_RECVING ||
+	    ssif_bmc->state == SSIF_SMBUS_CMD) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected READ PROCESSED in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_BAD_SMBUS;
+	}
+
+	handle_read_processed(ssif_bmc, val);
+}
+
+static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	ssif_bmc->msg_idx = 0;
+
+	if (ssif_bmc->state == SSIF_READY || ssif_bmc->state == SSIF_SMBUS_CMD) {
+		ssif_bmc->state = SSIF_START;
+
+	} else if (ssif_bmc->state == SSIF_START ||
+		   ssif_bmc->state == SSIF_REQ_RECVING ||
+		   ssif_bmc->state == SSIF_RES_SENDING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected WRITE REQUEST in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_BAD_SMBUS;
+	}
+}
+
+static void on_write_received_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY || ssif_bmc->state == SSIF_RES_SENDING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected WRITE RECEIVED in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_BAD_SMBUS;
+	} else if (ssif_bmc->state == SSIF_START) {
+		ssif_bmc->state = SSIF_SMBUS_CMD;
+	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+		ssif_bmc->state = SSIF_REQ_RECVING;
+	}
+
+	/* This is response sending state */
+	if (ssif_bmc->state == SSIF_REQ_RECVING) {
+		if (ssif_bmc->response_in_progress) {
+			/*
+			 * As per spec, it is generic management software or SSIF drivers to take
+			 * care of issuing new request before the prior requests completed.
+			 * So just abort everything here and wait for next new request
+			 */
+			dev_warn(&ssif_bmc->client->dev,
+				 "Warn: SSIF new request with pending response, aborting ...");
+			ssif_bmc->aborting = true;
+			complete_response(ssif_bmc);
+		}
+
+		handle_write_received(ssif_bmc, val);
+	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+		process_smbus_cmd(ssif_bmc, val);
+	}
+}
+
+static void on_stop_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_SMBUS_CMD) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected SLAVE STOP in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+
+	} else if (ssif_bmc->state == SSIF_BAD_SMBUS) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s received SLAVE STOP from bad state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+
+	} else if (ssif_bmc->state == SSIF_REQ_RECVING) {
+		/* A BMC that receives an invalid request drop the data for the write
+		 * transaction and any further transactions (read or write) until
+		 * the next valid read or write Start transaction is received
+		 */
+		if (!validate_request(ssif_bmc))
+			ssif_bmc->aborting = true;
+
+		if (!ssif_bmc->aborting &&
+		    (ssif_bmc->smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+		     ssif_bmc->smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_END))
+			handle_request(ssif_bmc);
+	}
+
+	ssif_bmc->state = SSIF_READY;
+	/* Reset message index */
+	ssif_bmc->msg_idx = 0;
+}
+
+/*
+ * Callback function to handle I2C slave events
+ */
+static int ssif_bmc_cb(struct i2c_client *client, enum i2c_slave_event event, u8 *val)
+{
+	unsigned long flags;
+	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+
+	switch (event) {
+	case I2C_SLAVE_READ_REQUESTED:
+		on_read_requested_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_WRITE_REQUESTED:
+		on_write_requested_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_READ_PROCESSED:
+		on_read_processed_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_WRITE_RECEIVED:
+		on_write_received_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_STOP:
+		on_stop_event(ssif_bmc, val);
+		break;
+
+	default:
+		dev_warn(&ssif_bmc->client->dev, "Warn: Unknown i2c slave event, aborting ...\n");
+		ssif_bmc->aborting = true;
+		break;
+	}
+
+	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+	return 0;
+}
+
+static int ssif_bmc_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	struct ssif_bmc_ctx *ssif_bmc;
+	int ret;
+
+	ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
+	if (!ssif_bmc)
+		return -ENOMEM;
+
+	spin_lock_init(&ssif_bmc->lock);
+
+	init_waitqueue_head(&ssif_bmc->wait_queue);
+	ssif_bmc->request_available = false;
+	ssif_bmc->response_in_progress = false;
+
+	/* Register misc device interface */
+	ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
+	ssif_bmc->miscdev.name = DEVICE_NAME;
+	ssif_bmc->miscdev.fops = &ssif_bmc_fops;
+	ssif_bmc->miscdev.parent = &client->dev;
+	ret = misc_register(&ssif_bmc->miscdev);
+	if (ret)
+		goto out;
+
+	ssif_bmc->client = client;
+	ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
+
+	/* Register I2C slave */
+	i2c_set_clientdata(client, ssif_bmc);
+	ret = i2c_slave_register(client, ssif_bmc_cb);
+	if (ret) {
+		misc_deregister(&ssif_bmc->miscdev);
+		goto out;
+	}
+
+	return 0;
+out:
+	devm_kfree(&client->dev, ssif_bmc);
+	return ret;
+}
+
+static int ssif_bmc_remove(struct i2c_client *client)
+{
+	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
+
+	i2c_slave_unregister(client);
+	misc_deregister(&ssif_bmc->miscdev);
+
+	return 0;
+}
+
+static const struct of_device_id ssif_bmc_match[] = {
+	{ .compatible = "ampere,ssif-bmc" },
+	{ },
+};
+
+static const struct i2c_device_id ssif_bmc_id[] = {
+	{ DEVICE_NAME, 0 },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(i2c, ssif_bmc_id);
+
+static struct i2c_driver ssif_bmc_driver = {
+	.driver         = {
+		.name           = DEVICE_NAME,
+		.of_match_table = ssif_bmc_match,
+	},
+	.probe          = ssif_bmc_probe,
+	.remove         = ssif_bmc_remove,
+	.id_table       = ssif_bmc_id,
+};
+
+module_i2c_driver(ssif_bmc_driver);
+
+MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
+MODULE_AUTHOR("Chuong Tran <chuong@os.amperecomputing.com>");
+MODULE_DESCRIPTION("Linux device driver of the BMC IPMI SSIF interface.");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/char/ipmi/ssif_bmc.h b/drivers/char/ipmi/ssif_bmc.h
new file mode 100644
index 000000000000..b63e40a4b900
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * The driver for BMC side of SSIF interface
+ *
+ * Copyright (c) 2021, Ampere Computing LLC
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef __SSIF_BMC_H__
+#define __SSIF_BMC_H__
+
+#define DEVICE_NAME				"ipmi-ssif-host"
+
+#define GET_8BIT_ADDR(addr_7bit)		(((addr_7bit) << 1) & 0xff)
+
+/* A standard SMBus Transaction is limited to 32 data bytes */
+#define MAX_PAYLOAD_PER_TRANSACTION		32
+
+#define MAX_IPMI_DATA_PER_START_TRANSACTION	30
+#define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION	31
+
+#define SSIF_IPMI_SINGLEPART_WRITE		0x2
+#define SSIF_IPMI_SINGLEPART_READ		0x3
+#define SSIF_IPMI_MULTIPART_WRITE_START		0x6
+#define SSIF_IPMI_MULTIPART_WRITE_MIDDLE	0x7
+#define SSIF_IPMI_MULTIPART_WRITE_END		0x8
+#define SSIF_IPMI_MULTIPART_READ_START		0x3
+#define SSIF_IPMI_MULTIPART_READ_MIDDLE		0x9
+
+#define MSG_PAYLOAD_LEN_MAX			252
+
+struct ssif_msg {
+	u8 len;
+	u8 netfn_lun;
+	u8 cmd;
+	u8 payload[MSG_PAYLOAD_LEN_MAX];
+} __packed;
+
+static inline u32 ssif_msg_len(struct ssif_msg *ssif_msg)
+{
+	return ssif_msg->len + 1;
+}
+
+/*
+ * SSIF internal states:
+ *   SSIF_READY         0x00 : Ready state
+ *   SSIF_START         0x01 : Start smbus transaction
+ *   SSIF_SMBUS_CMD     0x02 : Received SMBus command
+ *   SSIF_REQ_RECVING   0x03 : Receiving request
+ *   SSIF_RES_SENDING   0x04 : Sending response
+ *   SSIF_BAD_SMBUS     0x05 : Bad SMbus transaction
+ */
+enum ssif_state {
+	SSIF_READY,
+	SSIF_START,
+	SSIF_SMBUS_CMD,
+	SSIF_REQ_RECVING,
+	SSIF_RES_SENDING,
+	SSIF_BAD_SMBUS,
+	SSIF_STATE_MAX
+};
+
+struct ssif_bmc_ctx {
+	struct i2c_client	*client;
+	struct miscdevice	miscdev;
+	size_t			msg_idx;
+	bool			pec_support;
+	/* ssif bmc spinlock */
+	spinlock_t		lock;
+	wait_queue_head_t	wait_queue;
+	u8			running;
+	enum ssif_state		state;
+	u8			smbus_cmd;
+	/* Flag to abort current process */
+	bool			aborting;
+	/* Flag to identify a Multi-part Read Transaction */
+	bool			is_singlepart_read;
+	u8			nbytes_processed;
+	u8			remain_len;
+	u8			recv_len;
+	/* Block Number of a Multi-part Read Transaction */
+	u8			block_num;
+	bool			request_available;
+	bool			response_in_progress;
+	/* Response buffer for Multi-part Read Transaction */
+	u8			response_buf[MAX_PAYLOAD_PER_TRANSACTION];
+	struct ssif_msg		response;
+	struct ssif_msg		request;
+};
+
+static inline struct ssif_bmc_ctx *to_ssif_bmc(struct file *file)
+{
+	return container_of(file->private_data, struct ssif_bmc_ctx, miscdev);
+}
+#endif /* __SSIF_BMC_H__ */
-- 
2.28.0

[PATCH v5 3/3] bindings: ipmi: Add binding for SSIF BMC driver

[Quan Nguyen]

Add device tree binding document for the SSIF BMC driver.

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

v4:
  + Fix warning with dt_binding_check [Rob]
  + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml [Quan]

v3:
  + Switched to use DT schema format [Rob]

v2:
  + None

 .../devicetree/bindings/ipmi/ssif-bmc.yaml    | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml

diff --git a/Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml b/Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
new file mode 100644
index 000000000000..917a577c2f29
--- /dev/null
+++ b/Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/ipmi/ssif-bmc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SSIF IPMI BMC interface
+
+description: SSIF IPMI BMC device bindings
+
+maintainers:
+  - Quan Nguyen <quan@os.amperecomputing.com>
+
+properties:
+  compatible:
+    enum:
+      - ampere,ssif-bmc
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ssif-bmc@10 {
+            compatible = "ampere,ssif-bmc";
+            reg = <0x10>;
+        };
+    };
-- 
2.28.0

Re: [PATCH v5 3/3] bindings: ipmi: Add binding for SSIF BMC driver

[Rob Herring]

On Wed, 14 Jul 2021 10:38:33 +0700, Quan Nguyen wrote:
> Add device tree binding document for the SSIF BMC driver.
> 
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> ---
> v5:
>   + None
> 
> v4:
>   + Fix warning with dt_binding_check [Rob]
>   + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml [Quan]
> 
> v3:
>   + Switched to use DT schema format [Rob]
> 
> v2:
>   + None
> 
>  .../devicetree/bindings/ipmi/ssif-bmc.yaml    | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH v5 3/3] bindings: ipmi: Add binding for SSIF BMC driver

[Quan Nguyen]

On 16/07/2021 00:43, Rob Herring wrote:
> On Wed, 14 Jul 2021 10:38:33 +0700, Quan Nguyen wrote:
>> Add device tree binding document for the SSIF BMC driver.
>>
>> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
>> ---
>> v5:
>>    + None
>>
>> v4:
>>    + Fix warning with dt_binding_check [Rob]
>>    + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml [Quan]
>>
>> v3:
>>    + Switched to use DT schema format [Rob]
>>
>> v2:
>>    + None
>>
>>   .../devicetree/bindings/ipmi/ssif-bmc.yaml    | 38 +++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
>>
> 
> Reviewed-by: Rob Herring <robh@kernel.org>
> 

Thanks Rob.

Re: [PATCH v5 0/3] Add SSIF BMC driver

[Corey Minyard]

On Wed, Jul 14, 2021 at 10:38:30AM +0700, Quan Nguyen wrote:
> This series add support the SSIF BMC driver which is to perform in-band
> IPMI communication with their host in management (BMC) side.
> 
> SSIF BMC driver in this series is tested with Aspeed AST2500.

Ok, I have queued this and added Rob's review.  Five versions, you had
to work for this one :).

Thanks,

-corey

> 
> v5:
>   + Correct the patches order to fix the bisect issue found by
>   kernel build robot
> 
> v4:
>   + Fix recursive spinlock                                      [Graeme]
>   + Send response with Completion code 0xFF when aborting         [Quan]
>   + Fix warning with dt_binding_check                              [Rob]
>   + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml                  [Quan]
>   + Added bounding check on SMBus writes and the whole request     [Dan]
>   + Moved buffer to end of struct ssif_bmc_ctx to avoid context
>     corruption if somehow buffer is written past the end           [Dan]
>   + Return -EINVAL if userspace buffer too small, dont
>     silence truncate                                       [Corey, Joel]
>   + Not necessary to check NONBLOCK in lock                      [Corey]
>   + Enforce one user at a time                                    [Joel]
>   + Reject write with invalid response length from userspace     [Corey]
>   + Add state machines for better ssif bmc state handling         [Quan]
>   + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
>     SSIF BMC driver                                               [Quan]
>   + Change compatible string "aspeed,ast2500-ssif-bmc" to
>     "ampere,ssif-bmc"                                             [Quan]
>   + Toggle Slave enable in i2c-aspeed to turn on/off slave mode   [Ryan]
>   + Added slave_enable() to struct i2c_algorithm to control
>     slave mode and to address the recursive spinlock      [Graeme, Ryan]
>   + Abort current request with invalid SMBus write or
>     invalid command                                               [Quan]
>   + Abort all request if there is pending response                [Quan]
>   + Changed validate_pec() to validate_request()                  [Quan]
>   + Add unsupported_smbus_cmd() to handle unknown SMBus command   [Quan]
>   + Print internal state string for ease investigating issue      [Quan]
>   + Move to READY state on SLAVE_STOP event                       [Quan]
>   + Change initilize_transfer() to process_smbus_cmd()            [Quan]
>   + Introduce functions for each slave event                      [Quan]
> 
> v3:
>   + Switched binding doc to use DT schema format [Rob]
>   + Splited into generic ssif_bmc and aspeed-specific [Corey, Joel]
>   + Removed redundant license info [Joel]
>   + Switched to use traditional if-else [Joel]
>   + Removed unused ssif_bmc_ioctl() [Joel]
>   + Made handle_request()/complete_response() to return void [Joel]
>   + Refactored send_ssif_bmc_response()/receive_ssif_bmc_request()
>   [Corey]
>   + Remove mutex [Corey]
>   + Use spin_lock/unlock_irqsave/restore in callback [Corey]
>   + Removed the unnecessary memset [Corey]
>   + Switch to use dev_err() [Corey]
>   + Combine mask/unmask two interrupts together [Corey]
>   + Fixed unhandled Tx done with NAK [Quan]
>   + Late ack'ed Tx done w/wo Ack irq [Quan]
>   + Use aspeed-specific exported aspeed_set_slave_busy() when slave busy
>   to fix the deadlock [Graeme, Philipp, Quan]
>   + Clean buffer for last multipart read [Quan]
>   + Handle unknown incoming command [Quan]
> 
> v2:
>   + Fixed compiling error with COMPILE_TEST for arc
> 
> Quan Nguyen (3):
>   i2c: aspeed: Add slave_enable() to toggle slave mode
>   ipmi: ssif_bmc: Add SSIF BMC driver
>   bindings: ipmi: Add binding for SSIF BMC driver
> 
>  .../devicetree/bindings/ipmi/ssif-bmc.yaml    |  38 +
>  drivers/char/ipmi/Kconfig                     |  11 +
>  drivers/char/ipmi/Makefile                    |   1 +
>  drivers/char/ipmi/ssif_bmc.c                  | 781 ++++++++++++++++++
>  drivers/char/ipmi/ssif_bmc.h                  | 106 +++
>  drivers/i2c/busses/i2c-aspeed.c               |  20 +
>  include/linux/i2c.h                           |   2 +
>  7 files changed, 959 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
>  create mode 100644 drivers/char/ipmi/ssif_bmc.c
>  create mode 100644 drivers/char/ipmi/ssif_bmc.h
> 
> -- 
> 2.28.0
> 

Re: [PATCH v5 0/3] Add SSIF BMC driver

[Quan Nguyen]

On 16/07/2021 06:32, Corey Minyard wrote:
> On Wed, Jul 14, 2021 at 10:38:30AM +0700, Quan Nguyen wrote:
>> This series add support the SSIF BMC driver which is to perform in-band
>> IPMI communication with their host in management (BMC) side.
>>
>> SSIF BMC driver in this series is tested with Aspeed AST2500.
> 
> Ok, I have queued this and added Rob's review.  Five versions, you had
> to work for this one :).
> 
> Thanks,
> 
> -corey
> 
Thank you very much for your help in these version :)
- Quan

>>
>> v5:
>>    + Correct the patches order to fix the bisect issue found by
>>    kernel build robot
>>
>> v4:
>>    + Fix recursive spinlock                                      [Graeme]
>>    + Send response with Completion code 0xFF when aborting         [Quan]
>>    + Fix warning with dt_binding_check                              [Rob]
>>    + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml                  [Quan]
>>    + Added bounding check on SMBus writes and the whole request     [Dan]
>>    + Moved buffer to end of struct ssif_bmc_ctx to avoid context
>>      corruption if somehow buffer is written past the end           [Dan]
>>    + Return -EINVAL if userspace buffer too small, dont
>>      silence truncate                                       [Corey, Joel]
>>    + Not necessary to check NONBLOCK in lock                      [Corey]
>>    + Enforce one user at a time                                    [Joel]
>>    + Reject write with invalid response length from userspace     [Corey]
>>    + Add state machines for better ssif bmc state handling         [Quan]
>>    + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
>>      SSIF BMC driver                                               [Quan]
>>    + Change compatible string "aspeed,ast2500-ssif-bmc" to
>>      "ampere,ssif-bmc"                                             [Quan]
>>    + Toggle Slave enable in i2c-aspeed to turn on/off slave mode   [Ryan]
>>    + Added slave_enable() to struct i2c_algorithm to control
>>      slave mode and to address the recursive spinlock      [Graeme, Ryan]
>>    + Abort current request with invalid SMBus write or
>>      invalid command                                               [Quan]
>>    + Abort all request if there is pending response                [Quan]
>>    + Changed validate_pec() to validate_request()                  [Quan]
>>    + Add unsupported_smbus_cmd() to handle unknown SMBus command   [Quan]
>>    + Print internal state string for ease investigating issue      [Quan]
>>    + Move to READY state on SLAVE_STOP event                       [Quan]
>>    + Change initilize_transfer() to process_smbus_cmd()            [Quan]
>>    + Introduce functions for each slave event                      [Quan]
>>
>> v3:
>>    + Switched binding doc to use DT schema format [Rob]
>>    + Splited into generic ssif_bmc and aspeed-specific [Corey, Joel]
>>    + Removed redundant license info [Joel]
>>    + Switched to use traditional if-else [Joel]
>>    + Removed unused ssif_bmc_ioctl() [Joel]
>>    + Made handle_request()/complete_response() to return void [Joel]
>>    + Refactored send_ssif_bmc_response()/receive_ssif_bmc_request()
>>    [Corey]
>>    + Remove mutex [Corey]
>>    + Use spin_lock/unlock_irqsave/restore in callback [Corey]
>>    + Removed the unnecessary memset [Corey]
>>    + Switch to use dev_err() [Corey]
>>    + Combine mask/unmask two interrupts together [Corey]
>>    + Fixed unhandled Tx done with NAK [Quan]
>>    + Late ack'ed Tx done w/wo Ack irq [Quan]
>>    + Use aspeed-specific exported aspeed_set_slave_busy() when slave busy
>>    to fix the deadlock [Graeme, Philipp, Quan]
>>    + Clean buffer for last multipart read [Quan]
>>    + Handle unknown incoming command [Quan]
>>
>> v2:
>>    + Fixed compiling error with COMPILE_TEST for arc
>>
>> Quan Nguyen (3):
>>    i2c: aspeed: Add slave_enable() to toggle slave mode
>>    ipmi: ssif_bmc: Add SSIF BMC driver
>>    bindings: ipmi: Add binding for SSIF BMC driver
>>
>>   .../devicetree/bindings/ipmi/ssif-bmc.yaml    |  38 +
>>   drivers/char/ipmi/Kconfig                     |  11 +
>>   drivers/char/ipmi/Makefile                    |   1 +
>>   drivers/char/ipmi/ssif_bmc.c                  | 781 ++++++++++++++++++
>>   drivers/char/ipmi/ssif_bmc.h                  | 106 +++
>>   drivers/i2c/busses/i2c-aspeed.c               |  20 +
>>   include/linux/i2c.h                           |   2 +
>>   7 files changed, 959 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
>>   create mode 100644 drivers/char/ipmi/ssif_bmc.c
>>   create mode 100644 drivers/char/ipmi/ssif_bmc.h
>>
>> -- 
>> 2.28.0
>>