Message-Id: <20200121160114.60007-15-mika.westerberg@linux.intel.com>
Date:   Tue, 21 Jan 2020 19:00:50 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Lee Jones <lee.jones@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Zha Qipeng <qipeng.zha@...el.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Mark Brown <broonie@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 14/38] platform/x86: intel_scu_ipc: Introduce new SCU IPC API

The current SCU IPC API has been operating on a single instance and
there has been no way to pin the providing module in place when the SCU
IPC is in use.

This implements a new API that takes the SCU IPC instance as first
parameter (NULL means the single instance is being used). The SCU IPC
instance can be retrieved by calling new function
intel_scu_ipc_dev_get() that take care of pinning the providing module
in place as long as intel_scu_ipc_dev_put() is not called.

The old API is left there to support existing users which cannot be
converted easily but it is put to a separate header that is subject to
be removed eventually. Subsequent patches will convert most of the users
to the new API.

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 arch/x86/include/asm/intel_scu_ipc.h        |  74 +++----
 arch/x86/include/asm/intel_scu_ipc_legacy.h |  76 +++++++
 drivers/platform/x86/intel_scu_ipc.c        | 219 ++++++++++++++++----
 drivers/platform/x86/intel_scu_pcidrv.c     |   7 +-
 4 files changed, 287 insertions(+), 89 deletions(-)
 create mode 100644 arch/x86/include/asm/intel_scu_ipc_legacy.h

diff --git a/arch/x86/include/asm/intel_scu_ipc.h b/arch/x86/include/asm/intel_scu_ipc.h
index 252ea0046f16..ce2ad516f0f9 100644
--- a/arch/x86/include/asm/intel_scu_ipc.h
+++ b/arch/x86/include/asm/intel_scu_ipc.h
@@ -1,9 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_X86_INTEL_SCU_IPC_H_
-#define  _ASM_X86_INTEL_SCU_IPC_H_
+#define _ASM_X86_INTEL_SCU_IPC_H_
 
 #include <linux/ioport.h>
-#include <linux/notifier.h>
 
 #define IPCMSG_INDIRECT_READ	0x02
 #define IPCMSG_INDIRECT_WRITE	0x05
@@ -21,6 +20,7 @@
 	#define IPC_CMD_VRTC_SETALARM     2 /* Set alarm */
 
 struct device;
+struct intel_scu_ipc_dev;
 
 /**
  * struct intel_scu_ipc_pdata - Platform data for SCU IPC
@@ -32,47 +32,39 @@ struct intel_scu_ipc_pdata {
 	int irq;
 };
 
-int intel_scu_ipc_register(struct device *dev,
-			   const struct intel_scu_ipc_pdata *pdata);
-
-/* Read single register */
-int intel_scu_ipc_ioread8(u16 addr, u8 *data);
-
-/* Read a vector */
-int intel_scu_ipc_readv(u16 *addr, u8 *data, int len);
-
-/* Write single register */
-int intel_scu_ipc_iowrite8(u16 addr, u8 data);
-
-/* Write a vector */
-int intel_scu_ipc_writev(u16 *addr, u8 *data, int len);
-
-/* Update single register based on the mask */
-int intel_scu_ipc_update_register(u16 addr, u8 data, u8 mask);
-
-/* Issue commands to the SCU with or without data */
-int intel_scu_ipc_simple_command(int cmd, int sub);
-int intel_scu_ipc_command(int cmd, int sub, u32 *in, int inlen,
-			  u32 *out, int outlen);
-
-extern struct blocking_notifier_head intel_scu_notifier;
-
-static inline void intel_scu_notifier_add(struct notifier_block *nb)
-{
-	blocking_notifier_chain_register(&intel_scu_notifier, nb);
-}
-
-static inline void intel_scu_notifier_remove(struct notifier_block *nb)
-{
-	blocking_notifier_chain_unregister(&intel_scu_notifier, nb);
-}
-
-static inline int intel_scu_notifier_post(unsigned long v, void *p)
+struct intel_scu_ipc_dev *
+intel_scu_ipc_register(struct device *dev, const struct intel_scu_ipc_pdata *pdata);
+
+struct intel_scu_ipc_dev *intel_scu_ipc_dev_get(void);
+void intel_scu_ipc_dev_put(struct intel_scu_ipc_dev *scu);
+struct intel_scu_ipc_dev *devm_intel_scu_ipc_dev_get(struct device *dev);
+
+int intel_scu_ipc_dev_ioread8(struct intel_scu_ipc_dev *scu, u16 addr,
+			      u8 *data);
+int intel_scu_ipc_dev_iowrite8(struct intel_scu_ipc_dev *scu, u16 addr,
+			       u8 data);
+int intel_scu_ipc_dev_readv(struct intel_scu_ipc_dev *scu, u16 *addr,
+			    u8 *data, size_t len);
+int intel_scu_ipc_dev_writev(struct intel_scu_ipc_dev *scu, u16 *addr,
+			     u8 *data, size_t len);
+
+int intel_scu_ipc_dev_update(struct intel_scu_ipc_dev *scu, u16 addr,
+			     u8 data, u8 mask);
+
+int intel_scu_ipc_dev_simple_command(struct intel_scu_ipc_dev *scu, int cmd,
+				     int sub);
+int intel_scu_ipc_dev_command_with_size(struct intel_scu_ipc_dev *scu, int cmd,
+					int sub, const void *in, size_t inlen,
+					size_t size, void *out, size_t outlen);
+
+static inline int intel_scu_ipc_dev_command(struct intel_scu_ipc_dev *scu, int cmd,
+					    int sub, const void *in, size_t inlen,
+					    void *out, size_t outlen)
 {
-	return blocking_notifier_call_chain(&intel_scu_notifier, v, p);
+	return intel_scu_ipc_dev_command_with_size(scu, cmd, sub, in, inlen,
+						   inlen, out, outlen);
 }
 
-#define		SCU_AVAILABLE		1
-#define		SCU_DOWN		2
+#include <asm/intel_scu_ipc_legacy.h>
 
 #endif
diff --git a/arch/x86/include/asm/intel_scu_ipc_legacy.h b/arch/x86/include/asm/intel_scu_ipc_legacy.h
new file mode 100644
index 000000000000..3399ea8eea48
--- /dev/null
+++ b/arch/x86/include/asm/intel_scu_ipc_legacy.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_INTEL_SCU_IPC_LEGACY_H_
+#define _ASM_X86_INTEL_SCU_IPC_LEGACY_H_
+
+#include <linux/notifier.h>
+
+/* Don't call these in new code - they will be removed eventually */
+
+/* Read single register */
+static inline int intel_scu_ipc_ioread8(u16 addr, u8 *data)
+{
+	return intel_scu_ipc_dev_ioread8(NULL, addr, data);
+}
+
+/* Read a vector */
+static inline int intel_scu_ipc_readv(u16 *addr, u8 *data, int len)
+{
+	return intel_scu_ipc_dev_readv(NULL, addr, data, len);
+}
+
+/* Write single register */
+static inline int intel_scu_ipc_iowrite8(u16 addr, u8 data)
+{
+	return intel_scu_ipc_dev_iowrite8(NULL, addr, data);
+}
+
+/* Write a vector */
+static inline int intel_scu_ipc_writev(u16 *addr, u8 *data, int len)
+{
+	return intel_scu_ipc_dev_writev(NULL, addr, data, len);
+}
+
+/* Update single register based on the mask */
+static inline int intel_scu_ipc_update_register(u16 addr, u8 data, u8 mask)
+{
+	return intel_scu_ipc_dev_update(NULL, addr, data, mask);
+}
+
+/* Issue commands to the SCU with or without data */
+static inline int intel_scu_ipc_simple_command(int cmd, int sub)
+{
+	return intel_scu_ipc_dev_simple_command(NULL, cmd, sub);
+}
+
+static inline int intel_scu_ipc_command(int cmd, int sub, u32 *in, int inlen,
+					u32 *out, int outlen)
+{
+	/* New API takes both inlen and outlen as bytes so convert here */
+	size_t inbytes = inlen * sizeof(u32);
+	size_t outbytes = outlen * sizeof(u32);
+
+	return intel_scu_ipc_dev_command_with_size(NULL, cmd, sub, in, inbytes,
+						   inlen, out, outbytes);
+}
+
+extern struct blocking_notifier_head intel_scu_notifier;
+
+static inline void intel_scu_notifier_add(struct notifier_block *nb)
+{
+	blocking_notifier_chain_register(&intel_scu_notifier, nb);
+}
+
+static inline void intel_scu_notifier_remove(struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&intel_scu_notifier, nb);
+}
+
+static inline int intel_scu_notifier_post(unsigned long v, void *p)
+{
+	return blocking_notifier_call_chain(&intel_scu_notifier, v, p);
+}
+
+#define		SCU_AVAILABLE		1
+#define		SCU_DOWN		2
+
+#endif
diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
index 518b044d8ecb..391b65a4789e 100644
--- a/drivers/platform/x86/intel_scu_ipc.c
+++ b/drivers/platform/x86/intel_scu_ipc.c
@@ -19,6 +19,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/module.h>
 
 #include <asm/intel_scu_ipc.h>
 
@@ -78,6 +79,99 @@ static struct intel_scu_ipc_dev  ipcdev; /* Only one for now */
 
 static DEFINE_MUTEX(ipclock); /* lock used to prevent multiple call to SCU */
 
+/**
+ * intel_scu_ipc_dev_get() - Get SCU IPC instance
+ *
+ * The recommended new API takes SCU IPC instance as parameter and this
+ * function can be called by driver to get the instance. This also makes
+ * sure the driver providing the IPC functionality cannot be unloaded
+ * while the caller has the intance.
+ *
+ * Call intel_scu_ipc_dev_put() to release the instance.
+ *
+ * Returns %NULL if SCU IPC is not currently available.
+ */
+struct intel_scu_ipc_dev *intel_scu_ipc_dev_get(void)
+{
+	struct intel_scu_ipc_dev *scu = &ipcdev;
+
+	mutex_lock(&ipclock);
+	if (!scu->dev)
+		goto err_unlock;
+	if (!try_module_get(scu->dev->driver->owner))
+		goto err_unlock;
+	mutex_unlock(&ipclock);
+	return scu;
+
+err_unlock:
+	mutex_unlock(&ipclock);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(intel_scu_ipc_dev_get);
+
+/**
+ * intel_scu_ipc_dev_put() - Put SCU IPC instance
+ * @scu: SCU IPC instance
+ *
+ * This function releases the SCU IPC instance retrieved from
+ * intel_scu_ipc_dev_get() and allows the driver providing IPC to be
+ * unloaded.
+ */
+void intel_scu_ipc_dev_put(struct intel_scu_ipc_dev *scu)
+{
+	mutex_lock(&ipclock);
+	if (scu->dev)
+		module_put(scu->dev->driver->owner);
+	mutex_unlock(&ipclock);
+}
+EXPORT_SYMBOL_GPL(intel_scu_ipc_dev_put);
+
+struct intel_scu_ipc_devres {
+	struct intel_scu_ipc_dev *scu;
+};
+
+static void devm_intel_scu_ipc_dev_release(struct device *dev, void *res)
+{
+	struct intel_scu_ipc_devres *devres = res;
+	struct intel_scu_ipc_dev *scu = devres->scu;
+
+	intel_scu_ipc_dev_put(scu);
+}
+
+/**
+ * devm_intel_scu_ipc_dev_get() - Allocate managed SCU IPC device
+ * @dev: Device requesting the SCU IPC device
+ *
+ * The recommended new API takes SCU IPC instance as parameter and this
+ * function can be called by driver to get the instance. This also makes
+ * sure the driver providing the IPC functionality cannot be unloaded
+ * while the caller has the intance.
+ *
+ * Returns %NULL if SCU IPC is not currently available.
+ */
+struct intel_scu_ipc_dev *devm_intel_scu_ipc_dev_get(struct device *dev)
+{
+	struct intel_scu_ipc_devres *devres;
+	struct intel_scu_ipc_dev *scu;
+
+	devres = devres_alloc(devm_intel_scu_ipc_dev_release, sizeof(*devres),
+			      GFP_KERNEL);
+	if (!devres)
+		return NULL;
+
+	scu = intel_scu_ipc_dev_get();
+	if (!scu) {
+		devres_free(devres);
+		return NULL;
+	}
+
+	devres->scu = scu;
+	devres_add(dev, devres);
+
+	return scu;
+}
+EXPORT_SYMBOL_GPL(devm_intel_scu_ipc_dev_get);
+
 /*
  * Send ipc command
  * Command Register (Write Only):
@@ -168,15 +262,18 @@ static int intel_scu_ipc_check_status(struct intel_scu_ipc_dev *scu)
 }
 
 /* Read/Write power control(PMIC in Langwell, MSIC in PenWell) registers */
-static int pwr_reg_rdwr(u16 *addr, u8 *data, u32 count, u32 op, u32 id)
+static int pwr_reg_rdwr(struct intel_scu_ipc_dev *scu, u16 *addr, u8 *data,
+			u32 count, u32 op, u32 id)
 {
-	struct intel_scu_ipc_dev *scu = &ipcdev;
 	int nc;
 	u32 offset = 0;
 	int err;
 	u8 cbuf[IPC_WWBUF_SIZE];
 	u32 *wbuf = (u32 *)&cbuf;
 
+	if (!scu)
+		scu = &ipcdev;
+
 	memset(cbuf, 0, sizeof(cbuf));
 
 	mutex_lock(&ipclock);
@@ -220,7 +317,8 @@ static int pwr_reg_rdwr(u16 *addr, u8 *data, u32 count, u32 op, u32 id)
 }
 
 /**
- * intel_scu_ipc_ioread8		-	read a word via the SCU
+ * intel_scu_ipc_dev_ioread8() - Read a byte via the SCU
+ * @scu: Optional SCU IPC instance
  * @addr: Register on SCU
  * @data: Return pointer for read byte
  *
@@ -229,14 +327,15 @@ static int pwr_reg_rdwr(u16 *addr, u8 *data, u32 count, u32 op, u32 id)
  *
  * This function may sleep.
  */
-int intel_scu_ipc_ioread8(u16 addr, u8 *data)
+int intel_scu_ipc_dev_ioread8(struct intel_scu_ipc_dev *scu, u16 addr, u8 *data)
 {
-	return pwr_reg_rdwr(&addr, data, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_R);
+	return pwr_reg_rdwr(scu, &addr, data, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_R);
 }
-EXPORT_SYMBOL(intel_scu_ipc_ioread8);
+EXPORT_SYMBOL(intel_scu_ipc_dev_ioread8);
 
 /**
- * intel_scu_ipc_iowrite8		-	write a byte via the SCU
+ * intel_scu_ipc_dev_iowrite8() - Write a byte via the SCU
+ * @scu: Optional SCU IPC instance
  * @addr: Register on SCU
  * @data: Byte to write
  *
@@ -245,14 +344,15 @@ EXPORT_SYMBOL(intel_scu_ipc_ioread8);
  *
  * This function may sleep.
  */
-int intel_scu_ipc_iowrite8(u16 addr, u8 data)
+int intel_scu_ipc_dev_iowrite8(struct intel_scu_ipc_dev *scu, u16 addr, u8 data)
 {
-	return pwr_reg_rdwr(&addr, &data, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_W);
+	return pwr_reg_rdwr(scu, &addr, &data, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_W);
 }
-EXPORT_SYMBOL(intel_scu_ipc_iowrite8);
+EXPORT_SYMBOL(intel_scu_ipc_dev_iowrite8);
 
 /**
- * intel_scu_ipc_readvv		-	read a set of registers
+ * intel_scu_ipc_dev_readv() - Read a set of registers
+ * @scu: Optional SCU IPC instance
  * @addr: Register list
  * @data: Bytes to return
  * @len: Length of array
@@ -264,14 +364,16 @@ EXPORT_SYMBOL(intel_scu_ipc_iowrite8);
  *
  * This function may sleep.
  */
-int intel_scu_ipc_readv(u16 *addr, u8 *data, int len)
+int intel_scu_ipc_dev_readv(struct intel_scu_ipc_dev *scu, u16 *addr, u8 *data,
+			    size_t len)
 {
-	return pwr_reg_rdwr(addr, data, len, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_R);
+	return pwr_reg_rdwr(scu, addr, data, len, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_R);
 }
-EXPORT_SYMBOL(intel_scu_ipc_readv);
+EXPORT_SYMBOL(intel_scu_ipc_dev_readv);
 
 /**
- * intel_scu_ipc_writev		-	write a set of registers
+ * intel_scu_ipc_dev_writev() - Write a set of registers
+ * @scu: Optional SCU IPC instance
  * @addr: Register list
  * @data: Bytes to write
  * @len: Length of array
@@ -283,16 +385,18 @@ EXPORT_SYMBOL(intel_scu_ipc_readv);
  *
  * This function may sleep.
  */
-int intel_scu_ipc_writev(u16 *addr, u8 *data, int len)
+int intel_scu_ipc_dev_writev(struct intel_scu_ipc_dev *scu, u16 *addr, u8 *data,
+			     size_t len)
 {
-	return pwr_reg_rdwr(addr, data, len, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_W);
+	return pwr_reg_rdwr(scu, addr, data, len, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_W);
 }
-EXPORT_SYMBOL(intel_scu_ipc_writev);
+EXPORT_SYMBOL(intel_scu_ipc_dev_writev);
 
 /**
- * intel_scu_ipc_update_register	-	r/m/w a register
+ * intel_scu_ipc_dev_update() - Update a register
+ * @scu: Optional SCU IPC instance
  * @addr: Register address
- * @bits: Bits to update
+ * @data: Bits to update
  * @mask: Mask of bits to update
  *
  * Read-modify-write power control unit register. The first data argument
@@ -303,15 +407,17 @@ EXPORT_SYMBOL(intel_scu_ipc_writev);
  * This function may sleep. Locking between SCU accesses is handled
  * for the caller.
  */
-int intel_scu_ipc_update_register(u16 addr, u8 bits, u8 mask)
+int intel_scu_ipc_dev_update(struct intel_scu_ipc_dev *scu, u16 addr, u8 data,
+			     u8 mask)
 {
-	u8 data[2] = { bits, mask };
-	return pwr_reg_rdwr(&addr, data, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_M);
+	u8 tmp[2] = { data, mask };
+	return pwr_reg_rdwr(scu, &addr, tmp, 1, IPCMSG_PCNTRL, IPC_CMD_PCNTRL_M);
 }
-EXPORT_SYMBOL(intel_scu_ipc_update_register);
+EXPORT_SYMBOL(intel_scu_ipc_dev_update);
 
 /**
- * intel_scu_ipc_simple_command	-	send a simple command
+ * intel_scu_ipc_dev_simple_command() - Send a simple command
+ * @scu: Optional SCU IPC instance
  * @cmd: Command
  * @sub: Sub type
  *
@@ -322,11 +428,14 @@ EXPORT_SYMBOL(intel_scu_ipc_update_register);
  * This function may sleep. Locking for SCU accesses is handled for the
  * caller.
  */
-int intel_scu_ipc_simple_command(int cmd, int sub)
+int intel_scu_ipc_dev_simple_command(struct intel_scu_ipc_dev *scu, int cmd,
+				     int sub)
 {
-	struct intel_scu_ipc_dev *scu = &ipcdev;
 	int err;
 
+	if (!scu)
+		scu = &ipcdev;
+
 	mutex_lock(&ipclock);
 	if (scu->dev == NULL) {
 		mutex_unlock(&ipclock);
@@ -337,47 +446,65 @@ int intel_scu_ipc_simple_command(int cmd, int sub)
 	mutex_unlock(&ipclock);
 	return err;
 }
-EXPORT_SYMBOL(intel_scu_ipc_simple_command);
+EXPORT_SYMBOL(intel_scu_ipc_dev_simple_command);
 
 /**
- * intel_scu_ipc_command	-	command with data
+ * intel_scu_ipc_command_with_size() - Command with data
+ * @scu: Optional SCU IPC instance
  * @cmd: Command
  * @sub: Sub type
  * @in: Input data
- * @inlen: Input length in dwords
+ * @inlen: Input length in bytes
+ * @size: Input size written to the IPC command register in whatever
+ *	  units (dword, byte) the particular firmware requires. Normally
+ *	  should be the same as @inlen.
  * @out: Output data
- * @outlen: Output length in dwords
+ * @outlen: Output length in bytes
  *
  * Issue a command to the SCU which involves data transfers. Do the
  * data copies under the lock but leave it for the caller to interpret.
  */
-int intel_scu_ipc_command(int cmd, int sub, u32 *in, int inlen,
-			  u32 *out, int outlen)
+int intel_scu_ipc_dev_command_with_size(struct intel_scu_ipc_dev *scu, int cmd,
+					int sub, const void *in, size_t inlen,
+					size_t size, void *out, size_t outlen)
 {
-	struct intel_scu_ipc_dev *scu = &ipcdev;
+	size_t outbuflen = DIV_ROUND_UP(outlen, sizeof(u32));
+	size_t inbuflen = DIV_ROUND_UP(inlen, sizeof(u32));
+	u32 inbuf[4] = {};
 	int i, err;
 
+	if (inbuflen > 4 || outbuflen > 4)
+		return -EINVAL;
+
+	if (!scu)
+		scu = &ipcdev;
+
 	mutex_lock(&ipclock);
 	if (scu->dev == NULL) {
 		mutex_unlock(&ipclock);
 		return -ENODEV;
 	}
 
-	for (i = 0; i < inlen; i++)
-		ipc_data_writel(scu, *in++, 4 * i);
+	memcpy(inbuf, in, inlen);
+	for (i = 0; i < inbuflen; i++)
+		ipc_data_writel(scu, inbuf[i], 4 * i);
 
-	ipc_command(scu, (inlen << 16) | (sub << 12) | cmd);
+	ipc_command(scu, (size << 16) | (sub << 12) | cmd);
 	err = intel_scu_ipc_check_status(scu);
 
 	if (!err) {
-		for (i = 0; i < outlen; i++)
-			*out++ = ipc_data_readl(scu, 4 * i);
+		u32 outbuf[4] = {};
+
+		for (i = 0; i < outbuflen; i++)
+			outbuf[i] = ipc_data_readl(scu, 4 * i);
+
+		memcpy(out, outbuf, outlen);
 	}
 
 	mutex_unlock(&ipclock);
 	return err;
 }
-EXPORT_SYMBOL(intel_scu_ipc_command);
+EXPORT_SYMBOL(intel_scu_ipc_dev_command_with_size);
 
 /*
  * Interrupt handler gets called when ioc bit of IPC_COMMAND_REG set to 1
@@ -402,10 +529,12 @@ static irqreturn_t ioc(int irq, void *dev_id)
  * @dev: SCU device
  * @pdata: Platform specific data
  *
- * Call this function to initialize SCU IPC mechanism for @dev.
+ * Call this function to initialize SCU IPC mechanism for @dev. Returns SCU
+ * IPC instance or ERR_PTR() if there was an error. The caller may use the
+ * returned instance if it needs to do SCU IPC calls itself.
  */
-int intel_scu_ipc_register(struct device *dev,
-			   const struct intel_scu_ipc_pdata *pdata)
+struct intel_scu_ipc_dev *
+intel_scu_ipc_register(struct device *dev, const struct intel_scu_ipc_pdata *pdata)
 {
 	int err;
 	struct intel_scu_ipc_dev *scu = &ipcdev;
@@ -443,7 +572,7 @@ int intel_scu_ipc_register(struct device *dev,
 	scu->dev = dev;
 	mutex_unlock(&ipclock);
 
-	return 0;
+	return scu;
 
 err_unmap:
 	iounmap(scu->ipc_base);
@@ -452,6 +581,6 @@ int intel_scu_ipc_register(struct device *dev,
 err_unlock:
 	mutex_unlock(&ipclock);
 
-	return err;
+	return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(intel_scu_ipc_register);
diff --git a/drivers/platform/x86/intel_scu_pcidrv.c b/drivers/platform/x86/intel_scu_pcidrv.c
index dae5463f9714..52495ce14b9c 100644
--- a/drivers/platform/x86/intel_scu_pcidrv.c
+++ b/drivers/platform/x86/intel_scu_pcidrv.c
@@ -18,6 +18,7 @@ static int intel_scu_pci_probe(struct pci_dev *pdev,
 			       const struct pci_device_id *id)
 {
 	struct intel_scu_ipc_pdata pdata = {};
+	struct intel_scu_ipc_dev *scu;
 	int ret;
 
 	ret = pcim_enable_device(pdev);
@@ -27,9 +28,9 @@ static int intel_scu_pci_probe(struct pci_dev *pdev,
 	pdata.mem = pdev->resource[0];
 	pdata.irq = pdev->irq;
 
-	ret = intel_scu_ipc_register(&pdev->dev, &pdata);
-	if (ret)
-		return ret;
+	scu = intel_scu_ipc_register(&pdev->dev, &pdata);
+	if (IS_ERR(scu))
+		return PTR_ERR(scu);
 
 	intel_scu_devices_create();
 	return 0;
-- 
2.24.1

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