chip/stm32/usb_hid_keyboard: implement keyboard backlight control

Implement keyboard backlight control through HID output report. One
could enable CONFIG_USB_HID_KEYBOARD_BACKLIGHT to enable keyboard
backlight support for a given board. Target board must implement the
`void board_set_backlight(int brightness)` function in order correctly
set backlight.

BRANCH=none
BUG=b:37971411,b:63364143
TEST=with follow up CLs
     1. `make BOARD=hammer -j`
     2. `echo 10 > /sys/class/leds/hammer\:\:kbd_backlight/brightness`
        console shows 'Keyboard backlight set to 10%'

Change-Id: Ibeff510a0d996ddebf61b54ed6b500b02c35564a
Signed-off-by: Wei-Ning Huang <wnhuang@google.com>
Reviewed-on: https://chromium-review.googlesource.com/586348
Commit-Ready: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

6 files changed, 112 insertions, 20 deletions

diff --git a/chip/stm32/usb_hid.c b/chip/stm32/usb_hid.c
index 4a89d9573c..f24bdd5982 100644
--- a/chip/stm32/usb_hid.c
+++ b/chip/stm32/usb_hid.c
@@ -28,18 +28,33 @@ void hid_tx(int ep)
 	STM32_USB_EP(ep) = (STM32_USB_EP(ep) & EP_MASK);
 }
 
-void hid_reset(int ep, usb_uint *hid_ep_buf, int len)
+void hid_reset(int ep, usb_uint *hid_ep_tx_buf, int tx_len,
+	       usb_uint *hid_ep_rx_buf, int rx_len)
 {
 	int i;
-	/* HID interrupt endpoint 1 */
-	btable_ep[ep].tx_addr = usb_sram_addr(hid_ep_buf);
-	btable_ep[ep].tx_count = len;
-	for (i = 0; i < (len+1)/2; i++)
-		hid_ep_buf[i] = 0;
-	STM32_USB_EP(ep) = (ep << 0) /* Endpoint Address */ |
-		(3 << 4) /* TX Valid */ |
+	uint16_t ep_reg;
+
+	btable_ep[ep].tx_addr = usb_sram_addr(hid_ep_tx_buf);
+	btable_ep[ep].tx_count = tx_len;
+
+	/* STM32 USB SRAM needs to be accessed one U16 at a time */
+	for (i = 0; i < DIV_ROUND_UP(tx_len, 2); i++)
+		hid_ep_tx_buf[i] = 0;
+
+	ep_reg = (ep << 0) /* Endpoint Address */ |
+		EP_TX_VALID |
 		(3 << 9) /* interrupt EP */ |
-		(0 << 12) /* RX Disabled */;
+		EP_RX_DISAB;
+
+	/* Enable RX for output reports */
+	if (hid_ep_rx_buf && rx_len > 0) {
+		btable_ep[ep].rx_addr = usb_sram_addr(hid_ep_rx_buf);
+		btable_ep[ep].rx_count = ((rx_len + 1) / 2) << 10;
+
+		ep_reg |= EP_RX_VALID;  /* RX Valid */
+	}
+
+	STM32_USB_EP(ep) = ep_reg;
 }
 
 /*
diff --git a/chip/stm32/usb_hid_hw.h b/chip/stm32/usb_hid_hw.h
index 6e53559bd0..0133a0a16b 100644
--- a/chip/stm32/usb_hid_hw.h
+++ b/chip/stm32/usb_hid_hw.h
@@ -10,7 +10,8 @@
 
 /* internal callbacks for HID class drivers */
 void hid_tx(int ep);
-void hid_reset(int ep, usb_uint *hid_ep_buf, int len);
+void hid_reset(int ep, usb_uint *hid_ep_tx_buf, int tx_len,
+	       usb_uint *hid_ep_rx_buf, int rx_len);
 int hid_iface_request(usb_uint *ep0_buf_rx, usb_uint *ep0_buf_tx,
 		      const uint8_t *report_desc, int report_size,
 		      const struct usb_hid_descriptor *hid_desc);
diff --git a/chip/stm32/usb_hid_keyboard.c b/chip/stm32/usb_hid_keyboard.c
index 607fa17299..0d30783a1e 100644
--- a/chip/stm32/usb_hid_keyboard.c
+++ b/chip/stm32/usb_hid_keyboard.c
@@ -14,6 +14,7 @@
 #include "keyboard_config.h"
 #include "keyboard_protocol.h"
 #include "link_defs.h"
+#include "pwm.h"
 #include "queue.h"
 #include "registers.h"
 #include "task.h"
@@ -64,8 +65,15 @@ struct usb_hid_keyboard_report {
 #endif
 } __packed;
 
+struct usb_hid_keyboard_output_report {
+	uint8_t brightness;
+} __packed;
+
 #define HID_KEYBOARD_BOOT_SIZE 8
+
 #define HID_KEYBOARD_REPORT_SIZE sizeof(struct usb_hid_keyboard_report)
+#define HID_KEYBOARD_OUTPUT_REPORT_SIZE \
+	sizeof(struct usb_hid_keyboard_output_report)
 
 #define HID_KEYBOARD_EP_INTERVAL_MS 16 /* ms */
 
@@ -124,7 +132,11 @@ const struct usb_interface_descriptor USB_IFACE_DESC(USB_IFACE_HID_KEYBOARD) = {
 	.bDescriptorType = USB_DT_INTERFACE,
 	.bInterfaceNumber = USB_IFACE_HID_KEYBOARD,
 	.bAlternateSetting = 0,
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+	.bNumEndpoints = 2,
+#else
 	.bNumEndpoints = 1,
+#endif
 	.bInterfaceClass = USB_CLASS_HID,
 	.bInterfaceSubClass = USB_HID_SUBCLASS_BOOT,
 	.bInterfaceProtocol = USB_HID_PROTOCOL_KEYBOARD,
@@ -139,6 +151,17 @@ const struct usb_endpoint_descriptor USB_EP_DESC(USB_IFACE_HID_KEYBOARD, 81) = {
 	.bInterval = HID_KEYBOARD_EP_INTERVAL_MS /* ms polling interval */
 };
 
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+const struct usb_endpoint_descriptor USB_EP_DESC(USB_IFACE_HID_KEYBOARD, 02) = {
+	.bLength = USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType = USB_DT_ENDPOINT,
+	.bEndpointAddress = USB_EP_HID_KEYBOARD,
+	.bmAttributes = 0x03 /* Interrupt endpoint */,
+	.wMaxPacketSize = HID_KEYBOARD_OUTPUT_REPORT_SIZE,
+	.bInterval = HID_KEYBOARD_EP_INTERVAL_MS
+};
+#endif
+
 /* HID : Report Descriptor */
 static const uint8_t report_desc[] = {
 	0x05, 0x01, /* Usage Page (Generic Desktop) */
@@ -184,6 +207,18 @@ static const uint8_t report_desc[] = {
 	0x81, 0x01, /* Input (Constant), ;7-bit padding */
 #endif
 
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+	0xA1, 0x02, /* Collection (Logical) */
+	0x05, 0x14, /*   Usage Page (Alphanumeric Display) */
+	0x09, 0x46, /*   Usage (Display Brightness) */
+	0x95, 0x01, /*   Report Count (1) */
+	0x75, 0x08, /*   Report Size (8) */
+	0x15, 0x00, /*   Logical Minimum (0) */
+	0x25, 0x64, /*   Logical Maximum (100) */
+	0x91, 0x02, /*   Output (Data, Variable, Absolute) */
+	0xC0,       /* End Collection */
+#endif
+
 	0xC0        /* End Collection */
 };
 
@@ -201,11 +236,18 @@ const struct usb_hid_descriptor USB_CUSTOM_DESC_VAR(USB_IFACE_HID_KEYBOARD,
 	}}
 };
 
-#define EP_BUF_SIZE DIV_ROUND_UP(HID_KEYBOARD_REPORT_SIZE, 2)
+#define EP_TX_BUF_SIZE DIV_ROUND_UP(HID_KEYBOARD_REPORT_SIZE, 2)
+
+static usb_uint hid_ep_tx_buf[EP_TX_BUF_SIZE] __usb_ram;
+static volatile int hid_current_buf;
 
-static usb_uint hid_ep_buf[EP_BUF_SIZE] __usb_ram;
 static volatile int hid_ep_data_ready;
 
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+#define EP_RX_BUF_SIZE DIV_ROUND_UP(HID_KEYBOARD_OUTPUT_REPORT_SIZE, 2)
+static usb_uint hid_ep_rx_buf[EP_RX_BUF_SIZE] __usb_ram;
+#endif
+
 static struct usb_hid_keyboard_report report;
 
 static void keyboard_process_queue(void);
@@ -226,7 +268,7 @@ static void write_keyboard_report(void)
 		 * send the buffer: enable TX.
 		 */
 
-		memcpy_to_usbram((void *) usb_sram_addr(hid_ep_buf),
+		memcpy_to_usbram((void *) usb_sram_addr(hid_ep_tx_buf),
 				&report, sizeof(report));
 		STM32_TOGGLE_EP(USB_EP_HID_KEYBOARD, EP_TX_MASK,
 				EP_TX_VALID, 0);
@@ -240,11 +282,29 @@ static void write_keyboard_report(void)
 	usb_wake();
 }
 
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+
+static void hid_keyboard_rx(void)
+{
+	struct usb_hid_keyboard_output_report report;
+	memcpy_from_usbram(&report, (void *) usb_sram_addr(hid_ep_rx_buf),
+			   HID_KEYBOARD_OUTPUT_REPORT_SIZE);
+
+	CPRINTF("Keyboard backlight set to %d%%\n", report.brightness);
+
+	pwm_enable(PWM_CH_KBLIGHT, report.brightness > 0);
+	pwm_set_duty(PWM_CH_KBLIGHT, report.brightness);
+
+	STM32_TOGGLE_EP(USB_EP_HID_KEYBOARD, EP_TX_RX_MASK, EP_TX_RX_VALID, 0);
+}
+
+#endif
+
 static void hid_keyboard_tx(void)
 {
 	hid_tx(USB_EP_HID_KEYBOARD);
 	if (hid_ep_data_ready) {
-		memcpy_to_usbram((void *) usb_sram_addr(hid_ep_buf),
+		memcpy_to_usbram((void *) usb_sram_addr(hid_ep_tx_buf),
 				&report, sizeof(report));
 		STM32_TOGGLE_EP(USB_EP_HID_KEYBOARD, EP_TX_MASK,
 				EP_TX_VALID, 0);
@@ -260,8 +320,16 @@ static void hid_keyboard_event(enum usb_ep_event evt)
 	if (evt == USB_EVENT_RESET) {
 		protocol = HID_REPORT_PROTOCOL;
 
-		hid_reset(USB_EP_HID_KEYBOARD, hid_ep_buf,
-			HID_KEYBOARD_REPORT_SIZE);
+		hid_reset(USB_EP_HID_KEYBOARD,
+			  hid_ep_tx_buf,
+			  HID_KEYBOARD_REPORT_SIZE,
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+			  hid_ep_rx_buf,
+			  HID_KEYBOARD_OUTPUT_REPORT_SIZE
+#else
+			  NULL, 0
+#endif
+			  );
 		return;
 	}
 
@@ -269,7 +337,12 @@ static void hid_keyboard_event(enum usb_ep_event evt)
 		hook_call_deferred(&keyboard_process_queue_data, 0);
 }
 
-USB_DECLARE_EP(USB_EP_HID_KEYBOARD, hid_keyboard_tx, hid_keyboard_tx,
+USB_DECLARE_EP(USB_EP_HID_KEYBOARD, hid_keyboard_tx,
+#ifdef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+	       hid_keyboard_rx,
+#else
+	       hid_keyboard_tx,
+#endif
 	       hid_keyboard_event);
 
 static int hid_keyboard_iface_request(usb_uint *ep0_buf_rx,
diff --git a/chip/stm32/usb_hid_touchpad.c b/chip/stm32/usb_hid_touchpad.c
index f6624c24c7..a3174e4d94 100644
--- a/chip/stm32/usb_hid_touchpad.c
+++ b/chip/stm32/usb_hid_touchpad.c
@@ -310,7 +310,7 @@ static void hid_touchpad_event(enum usb_ep_event evt)
 {
 	if (evt == USB_EVENT_RESET)
 		hid_reset(USB_EP_HID_TOUCHPAD, hid_ep_buf,
-			  HID_TOUCHPAD_REPORT_SIZE);
+			  HID_TOUCHPAD_REPORT_SIZE, NULL, 0);
 	else if (evt == USB_EVENT_DEVICE_RESUME &&
 			queue_count(&report_queue) > 0)
 		hook_call_deferred(&hid_touchpad_process_queue_data, 0);
diff --git a/include/config.h b/include/config.h
index 270783ef48..07e6e34149 100644
--- a/include/config.h
+++ b/include/config.h
@@ -2677,6 +2677,9 @@
 /* Support USB HID keyboard interface. */
 #undef CONFIG_USB_HID_KEYBOARD
 
+/* Support USB HID keyboard backlight. */
+#undef CONFIG_USB_HID_KEYBOARD_BACKLIGHT
+
 /* Support USB HID touchpad interface. */
 #undef CONFIG_USB_HID_TOUCHPAD
 
diff --git a/include/usb_hid_touchpad.h b/include/usb_hid_touchpad.h
index d7d6dc0363..39b6277b96 100644
--- a/include/usb_hid_touchpad.h
+++ b/include/usb_hid_touchpad.h
@@ -5,8 +5,8 @@
  * USB HID definitions.
  */
 
-#ifndef __CROS_EC_USB_HID_KEYBOARD_H
-#define __CROS_EC_USB_HID_KEYBOARD_H
+#ifndef __CROS_EC_USB_HID_TOUCHPAD_H
+#define __CROS_EC_USB_HID_TOUCHPAD_H
 
 #define USB_HID_TOUCHPAD_TIMESTAMP_UNIT 100 /* usec */