Re: [PATCH v3 2/7] ipmi: ssif_bmc: Add SSIF BMC driver
From: Corey Minyard
Date: Wed May 19 2021 - 08:30:50 EST
On Wed, May 19, 2021 at 02:49:29PM +0700, Quan Nguyen wrote:
> 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@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> 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 | 605 +++++++++++++++++++++++++++++++++++
> drivers/char/ipmi/ssif_bmc.h | 93 ++++++
> 4 files changed, 710 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 07847d9a459a..ad5c5161bcd6 100644
> --- a/drivers/char/ipmi/Kconfig
> +++ b/drivers/char/ipmi/Kconfig
> @@ -133,6 +133,17 @@ 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 0822adc2ec41..d04a214d74c4 100644
> --- a/drivers/char/ipmi/Makefile
> +++ b/drivers/char/ipmi/Makefile
> @@ -27,3 +27,4 @@ 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..d0ea7059b1db
> --- /dev/null
> +++ b/drivers/char/ipmi/ssif_bmc.c
> @@ -0,0 +1,605 @@
> +// 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"
> +
> +/* 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) {
> + if (file->f_flags & O_NONBLOCK) {
There is no real need to check this under the lock. It would simplify
the end of this function if you checked this outside the lock.
> + ret = -EAGAIN;
> + goto out_unlock;
> + }
> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
> + ret = wait_event_interruptible(ssif_bmc->wait_queue,
> + ssif_bmc->request_available);
> + if (ret)
> + return ret;
> + spin_lock_irqsave(&ssif_bmc->lock, flags);
> + }
> +
> + count = min_t(ssize_t, ssif_msg_len(&ssif_bmc->request),
> + min_t(ssize_t, sizeof(struct ssif_msg), count));
Just curious, what happens if userland supplies a buffer that is too
small? Is data lost? In that case, I would think returning an error
here would be the better thing, as opposed to silently truncating the
message.
> + 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);
> + goto out;
> +
> +out_unlock:
> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
> +out:
> + 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) {
> + if (file->f_flags & O_NONBLOCK) {
Same comment as O_NONBLOCK before.
> + ret = -EAGAIN;
> + goto out_unlock;
> + }
> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
> + ret = wait_event_interruptible(ssif_bmc->wait_queue,
> + !ssif_bmc->response_in_progress);
> + if (ret)
> + goto out;
> + 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->set_ssif_bmc_status)
> + ssif_bmc->set_ssif_bmc_status(ssif_bmc, SSIF_BMC_READY);
> +
> +out_unlock:
> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
> +
> +out:
> + 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 message is now available so 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 handle_request(struct ssif_bmc_ctx *ssif_bmc)
> +{
> + if (ssif_bmc->set_ssif_bmc_status)
> + ssif_bmc->set_ssif_bmc_status(ssif_bmc, SSIF_BMC_BUSY);
> +
> + /* Request message is available to process */
> + ssif_bmc->request_available = true;
> + /*
> + * This is the new READ request.
> + */
> + wake_up_all(&ssif_bmc->wait_queue);
> +}
> +
> +/* 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);
> +}
> +
> +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,
> + "Error: Unexpected SMBus command received 0x%x\n", ssif_bmc->smbus_cmd);
> + 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,
> + "Error: Unexpected SMBus command received 0x%x\n",
> + ssif_bmc->smbus_cmd);
> + 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 smbus_cmd;
> +
> + buf = (u8 *)&ssif_bmc->request;
> + if (ssif_bmc->msg_idx >= sizeof(struct ssif_msg))
Shouldn't you abort the message if you get too much data? Otherwise you
get silent truncation.
> + return;
> +
> + smbus_cmd = ssif_bmc->smbus_cmd;
> + switch (smbus_cmd) {
> + case SSIF_IPMI_SINGLEPART_WRITE:
> + /* Single-part write */
> + buf[ssif_bmc->msg_idx - 1] = *val;
> + ssif_bmc->msg_idx++;
> +
> + break;
Generally you put the space after the break, not before. You did this
right before, but didn't from here down in the file.
> + case SSIF_IPMI_MULTIPART_WRITE_START:
> + /* Reset length to zero */
> + if (ssif_bmc->msg_idx == 1)
> + ssif_bmc->request.len = 0;
What happens if you get this and you are in the middle of a message?
> +
> + fallthrough;
> + case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
> + case SSIF_IPMI_MULTIPART_WRITE_END:
What happens if you get these and you are not in a message?
> + /* Multi-part write, 2nd byte received is length */
> + if (ssif_bmc->msg_idx == 1) {
> + ssif_bmc->request.len += *val;
> + ssif_bmc->recv_len = *val;
> + } 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,
> + "Error: Unexpected SMBus command received 0x%x\n", ssif_bmc->smbus_cmd);
> + break;
> + }
> +}
> +
> +static bool validate_pec(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;
> + return true;
> + }
> +
> + if ((ssif_bmc->msg_idx - 1) != (ssif_msg_len(&ssif_bmc->request) + 1))
> + goto error;
> +
> + /* 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;
> + return true;
> + }
> +
> + if ((ssif_bmc->msg_idx - 1 + index) != (ssif_msg_len(&ssif_bmc->request) + 1))
> + goto error;
> +
> + /* 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-bytes 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:
> + break;
> + }
> +
> + return ret;
> +error:
> + /* Do not expect to go to this case */
> + dev_err(&ssif_bmc->client->dev,
> + "Error: Unexpected length received %d\n", ssif_msg_len(&ssif_bmc->request));
> +
> + return false;
> +}
> +
> +static void complete_write_received(struct ssif_bmc_ctx *ssif_bmc)
> +{
> + u8 cmd = ssif_bmc->smbus_cmd;
> +
> + /* A BMC that receives an invalid PEC shall 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_pec(ssif_bmc)) {
> + dev_err(&ssif_bmc->client->dev, "Received invalid PEC\n");
> + return;
> + }
> +
> + if (cmd == SSIF_IPMI_SINGLEPART_WRITE || cmd == SSIF_IPMI_MULTIPART_WRITE_END)
> + handle_request(ssif_bmc);
> +}
> +
> +static void initialize_transfer(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 (ssif_bmc->smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
> + ssif_bmc->smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_START) {
> + /*
> + * The response can be delayed in BMC causing host SSIF driver
> + * to timeout and send a new request once BMC slave is ready.
> + * In that case check for pending response and clear it
> + */
> + if (ssif_bmc->response_in_progress) {
> + dev_err(&ssif_bmc->client->dev,
> + "Warn: SSIF new request with pending response");
> + complete_response(ssif_bmc);
> + }
> + } else if (unlikely(ssif_bmc->smbus_cmd != SSIF_IPMI_SINGLEPART_READ &&
> + ssif_bmc->smbus_cmd != SSIF_IPMI_MULTIPART_WRITE_MIDDLE &&
> + ssif_bmc->smbus_cmd != SSIF_IPMI_MULTIPART_WRITE_END &&
> + ssif_bmc->smbus_cmd != SSIF_IPMI_MULTIPART_READ_START &&
> + ssif_bmc->smbus_cmd != SSIF_IPMI_MULTIPART_READ_MIDDLE)) {
> + /* Unknown command, clear it */
> + dev_err(&ssif_bmc->client->dev, "Warn: Unknown SMBus command");
> + complete_response(ssif_bmc);
> + }
> +}
> +
> +/*
> + * 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);
> +
> + /* I2C Event Handler:
> + * I2C_SLAVE_READ_REQUESTED 0x0
> + * I2C_SLAVE_WRITE_REQUESTED 0x1
> + * I2C_SLAVE_READ_PROCESSED 0x2
> + * I2C_SLAVE_WRITE_RECEIVED 0x3
> + * I2C_SLAVE_STOP 0x4
> + */
> + switch (event) {
> + case I2C_SLAVE_READ_REQUESTED:
> + ssif_bmc->msg_idx = 0;
> + if (ssif_bmc->is_singlepart_read)
> + *val = ssif_bmc->response.len;
> + else
> + set_multipart_response_buffer(ssif_bmc, val);
> + break;
> +
> + case I2C_SLAVE_WRITE_REQUESTED:
> + ssif_bmc->msg_idx = 0;
> + break;
> +
> + case I2C_SLAVE_READ_PROCESSED:
> + handle_read_processed(ssif_bmc, val);
> + break;
> +
> + case I2C_SLAVE_WRITE_RECEIVED:
> + if (ssif_bmc->msg_idx)
> + handle_write_received(ssif_bmc, val);
> + else
> + initialize_transfer(ssif_bmc, val);
> +
> + break;
> +
> + case I2C_SLAVE_STOP:
> + if (ssif_bmc->last_event == I2C_SLAVE_WRITE_RECEIVED)
> + complete_write_received(ssif_bmc);
> + /* Reset message index */
> + ssif_bmc->msg_idx = 0;
> + break;
> +
> + default:
> + break;
> + }
> + ssif_bmc->last_event = event;
> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
> +
> + return 0;
> +}
> +
> +struct ssif_bmc_ctx *ssif_bmc_alloc(struct i2c_client *client, int sizeof_priv)
> +{
> + struct ssif_bmc_ctx *ssif_bmc;
> + int ret;
> +
> + ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc) + sizeof_priv, GFP_KERNEL);
> + if (!ssif_bmc)
> + return ERR_PTR(-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 ssif_bmc;
> +
> +out:
> + devm_kfree(&client->dev, ssif_bmc);
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(ssif_bmc_alloc);
> +
> +MODULE_AUTHOR("Chuong Tran <chuong@xxxxxxxxxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>");
> +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..eab540061f14
> --- /dev/null
> +++ b/drivers/char/ipmi/ssif_bmc.h
> @@ -0,0 +1,93 @@
> +/* 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)
> +
> +#define MSG_PAYLOAD_LEN_MAX 252
> +
> +/* 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
> +
> +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;
> +}
> +
> +#define SSIF_BMC_BUSY 0x01
> +#define SSIF_BMC_READY 0x02
> +
> +struct ssif_bmc_ctx {
> + struct i2c_client *client;
> + struct miscdevice miscdev;
> + u8 running;
> + u8 smbus_cmd;
> + struct ssif_msg request;
> + bool request_available;
> + struct ssif_msg response;
> + bool response_in_progress;
> + /* Response buffer for Multi-part Read Transaction */
> + u8 response_buf[MAX_PAYLOAD_PER_TRANSACTION];
> + /* 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;
> + size_t msg_idx;
> + enum i2c_slave_event last_event;
> + bool pec_support;
> + /* spinlock */
> + spinlock_t lock;
> + wait_queue_head_t wait_queue;
> + void (*set_ssif_bmc_status)(struct ssif_bmc_ctx *ssif_bmc, unsigned int flags);
> + void *priv;
> +};
> +
> +static inline struct ssif_bmc_ctx *to_ssif_bmc(struct file *file)
> +{
> + return container_of(file->private_data, struct ssif_bmc_ctx, miscdev);
> +}
> +
> +struct ssif_bmc_ctx *ssif_bmc_alloc(struct i2c_client *client, int sizeof_priv);
> +
> +#endif /* __SSIF_BMC_H__ */
> --
> 2.28.0
>