Input: psmouse - add delay when deactivating for SMBus mode

There is a period of time between the psmouse deactivate and the
ability to communicate with the SMBus companion. Insert a
sleep after the deactivate to account for the delay and ensure
the SMBus companion is responsive.

Attempting to read from the SMBus companion too quickly was causing
the touchpad on machines with an i801_smbus companion to stop working
after a sleep/resume cycle.

On resume the rmi4_smbus would fail with errors reading the SMBus version
number:
```
[5454] i2c_i801:i801_check_post:414: i801_smbus 0000:00:1f.3: No response
smbus_result: i2c-0 a=02c f=0000 c=fd BYTE_DATA rd res=-6
rmi4_smbus 0-002c: failed to get SMBus version number!
...
rmi4_f01 rmi4-00.fn01: Failed to restore normal operation: -6.
rmi4_f01 rmi4-00.fn01: Resume failed with code -6.
rmi4_physical rmi4-00: Failed to suspend functions: -6
rmi4_smbus 0-002c: Failed to resume device: -6
```
In this case the rmi_smb_get_version fails with -ENXIO if it happens too
soon after the preceding serio_resume -> psmouse_deactivate call.

On boot this issue could cause the touchpad to stay in the limited PS/2
mode. This only reproduced in 1 in 10 boots on the Lenovo T440p.
Failures in the log on boot would show up as:
```
psmouse serio1: synaptics: Trying to set up SMBus access
[122] i2c_i801:i801_check_post:437: i801_smbus 0000:00:1f.3: No response
psmouse serio1: synaptics: SMbus companion is not ready yet
```

Experimentation on the Lenovo T440p showed that a delay of 7-12ms on
resume allowed the companion to respond.

The 30ms delay in this patch was chosen based on the linux-input message:
Link: https://lore.kernel.org/all/BYAPR03MB47572F2C65E52ED673238D41B2439@BYAPR03MB4757.namprd03.prod.outlook.com/Signed-off-by: Jeffery Miller <jefferymiller@google.com>
Link: https://lore.kernel.org/r/20230726025256.81174-1-jefferymiller@google.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/psmouse-smbus.c

@@ -5,6 +5,7 @@
 
 #define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt
 
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/libps2.h>
@@ -118,13 +119,18 @@ static psmouse_ret_t psmouse_smbus_process_byte(struct psmouse *psmouse)
 	return PSMOUSE_FULL_PACKET;
 }
 
-static int psmouse_smbus_reconnect(struct psmouse *psmouse)
+static void psmouse_activate_smbus_mode(struct psmouse_smbus_dev *smbdev)
 {
-	struct psmouse_smbus_dev *smbdev = psmouse->private;
-
-	if (smbdev->need_deactivate)
-		psmouse_deactivate(psmouse);
+	if (smbdev->need_deactivate) {
+		psmouse_deactivate(smbdev->psmouse);
+		/* Give the device time to switch into SMBus mode */
+		msleep(30);
+	}
+}
 
+static int psmouse_smbus_reconnect(struct psmouse *psmouse)
+{
+	psmouse_activate_smbus_mode(psmouse->private);
 	return 0;
 }
 
@@ -257,8 +263,7 @@ int psmouse_smbus_init(struct psmouse *psmouse,
 		}
 	}
 
-	if (need_deactivate)
-		psmouse_deactivate(psmouse);
+	psmouse_activate_smbus_mode(smbdev);
 
 	psmouse->private = smbdev;
 	psmouse->protocol_handler = psmouse_smbus_process_byte;