簡要記錄了Qualcom MSM8xxx MDP Framebuffer驅動中的一些點。

Framebuffer裝置的sysfs

330static int msm_fb_create_sysfs(struct platform_device *pdev)

331{

332         int rc;

333         struct msm_fb_data_type *mfd = platform_get_drvdata(pdev);

334

335         rc = sysfs_create_group(&mfd->fbi->dev->kobj, &msm_fb_attr_group);

336         if (rc)

337                         MSM_FB_ERR("%s: sysfs group creation failed, rc=%d\n", __func__,

338                                         rc);

339         return rc;

340}

[email protected]:/sys/class/graphics/fb0 # ls -al

-rw-r--r-- root     root         4096 1970-06-27 09:37 bits_per_pixel

-rw-r--r-- root     root         4096 1970-06-27 09:37 blank

-rw-r--r-- root     root         4096 1970-06-27 09:37 console

-rw-r--r-- root     root         4096 1970-06-27 09:37 cursor

-r--r--r-- root     root         4096 1970-06-27 09:37 dev

-rw-r--r-- root     root         4096 1970-06-27 09:37 mode

-rw-r--r-- root     root         4096 1970-06-27 09:37 modes

-r--r--r-- root     root         4096 1970-06-27 09:37 msm_fb_type

-r--r--r-- root     root         4096 1970-06-27 09:37 name

-rw-r--r-- root     root         4096 1970-06-27 09:37 pan

drwxr-xr-x root     root              1970-06-27 08:28 power

-rw-r--r-- root     root         4096 1970-06-27 09:37 rotate

-rw-r--r-- root     root         4096 1970-06-27 09:37 state

-r--r--r-- root     root         4096 1970-06-27 09:37 stride

lrwxrwxrwx root     root              1970-06-27 09:37 subsystem -> ../../../../class/graphics

-rw-r--r-- root     root         4096 1970-06-27 08:28 uevent

-rw-r--r-- root     root         4096 1970-06-27 09:37 virtual_size

-r--r--r-- root     root         4096 1970-06-27 08:28 vsync_event

[email protected]:/sys/class/graphics/fb0 # cat msm_fb_type                        

mipi dsi cmd panel

[email protected]:/sys/class/graphics/fb0 # cat bits_per_pixel                     

32

130|[email protected]:/sys/class/graphics/fb0 # cat dev

29:0

[email protected]:/sys/class/graphics/fb0 # cat modes

U:480x854p-0

[email protected]:/sys/class/graphics/fb0 # cat name

msmfb42_90501

[email protected]:/sys/class/graphics/fb0 # cat stride

1920

[email protected]:/sys/class/graphics/fb0 # cat virtual_size                     

480,2566

cont_splash_done field

Add support for "Continuous Splash Screen" feature.

The image displayed on the screen by the android bootloaderdriver should continue till the android animation shows up.

Delay the display initialization for MDP, display dependent clocksand panel power on functions.

bootloader顯示的image在linux核心啟動過程中保持顯示在螢幕上，知道開機動畫顯示，即linux核心啟動過程中不要出現黑屏。

Early suspend & Early resume

Early suspend是有wakelock還佔有，系統還不能整體suspend，但是可以關閉螢幕、背光、輸入等；在Early suspended狀態時，重新開啟螢幕、背光和輸入，是為對應的early resume。

fb_register中相關設定如下：

1551                       mfd->early_suspend.suspend = msmfb_early_suspend;

1552                       mfd->early_suspend.resume = msmfb_early_resume;

1553                       mfd->early_suspend.level = EARLY_SUSPEND_LEVEL_DISABLE_FB - 2;

1554                       register_early_suspend(&mfd->early_suspend);

資料結構定義如下：

23/* The early_suspend structure defines suspend and resume hooks to be called

24 * when the user visible sleep state of the system changes, and a level to

25 * control the order. They can be used to turn off the screen and input

26 * devices that are not used for wakeup.

27 * Suspend handlers are called in low to high level order, resume handlers are

28 * called in the opposite order. If, when calling register_early_suspend,

29 * the suspend handlers have already been called without a matching call to the

30 * resume handlers, the suspend handler will be called directly from

31 * register_early_suspend. This direct call can violate the normal level order.

32 */

33enum {

34           EARLY_SUSPEND_LEVEL_BLANK_SCREEN = 50,

35           EARLY_SUSPEND_LEVEL_STOP_DRAWING = 100,

36           EARLY_SUSPEND_LEVEL_DISABLE_FB = 150,

37};

38struct early_suspend {

39#ifdef CONFIG_HAS_EARLYSUSPEND

40           struct list_head link;

41           int level;

42           void (*suspend)(struct early_suspend *h);

43           void (*resume)(struct early_suspend *h);

44#endif

45};

backlight

msm_fb_set_backlight以後是使用led_trigger呼叫真正led_classdev "wled"的brightnes_set去設定背光。

使用者態ioctl通過msm_fb_set_backlight呼叫到msm_fb_panel_data::set_backlight，

"lcd_backlight".brightness_set -> msm_fb_panel_data::set_backlight -> "bkl_trigger".led_trigger -> "wled".brightness_set。然後找真正操作硬體IC部分。

驅動中設定背光則是繞過"lcd_backlight"裝置直接通過backlight_worker工作執行到msm_fb_panel_data::set_backlight，然後-> "bkl_trigger".led_trigger -> "wled".brightness_set。

可以認為"lcd_backlight"是背光抽象裝置，通過led_trigger的led組對映到不同的led_classdev裝置

以三星DSI CMD屏為例：

In mipi_samsung.c

294static void mipi_samsung_set_backlight(struct msm_fb_data_type *mfd)

295{

296         if (!cci_fb_UpdateDone){

297                         printk("Taylor: No BL before LCM on\n");

298                         return;

299         }

300

301         pr_debug("Taylor: %s : Set BL:%d\n",__func__, mfd->bl_level);

302         if ((mipi_samsung_pdata->enable_wled_bl_ctrl)

303             && (wled_trigger_initialized)) {

304                         led_trigger_event(bkl_led_trigger, mfd->bl_level);

305                         return;

306         }

307}

kernel/drivers/leds/leds-pm8xxx.c

#define PM8XXX_LEDS_DEV_NAME       "pm8xxx-led"

2283static struct platform_driver pm8xxx_led_driver = {

2284       .probe                  = pm8xxx_led_probe,

2285       .remove                               = __devexit_p(pm8xxx_led_remove),

2286       .driver                   = {

2287                       .name   = PM8XXX_LEDS_DEV_NAME,

2288                       .owner = THIS_MODULE,

2289       },

2290};

pm8xxx_led_probe會對pm8038_led_info陣列中的每個led使用設定led_classdev欄位，並且初始化work item，然後使用led_classdev_register向系統註冊每個led裝置。

2197                       INIT_WORK(&led_dat->work, pm8xxx_led_work);

2198                       INIT_WORK(&led_dat->modework, pm8xxx_mode_work);

2199                       INIT_WORK(&led_dat->testwork, pm8xxx_test_work);

每個led的brightness_set欄位設定為pm8xxx_led_set。

1790static void pm8xxx_led_set(struct led_classdev *led_cdev,

1791       enum led_brightness value)

1792{

1793       struct    pm8xxx_led_data *led;

1794

1795       led = container_of(led_cdev, struct pm8xxx_led_data, cdev);

1796

1797       if (value < LED_OFF || value > led->cdev.max_brightness) {

1798                       dev_err(led->cdev.dev, "Invalid brightness value exceeds");

1799                       return;

1800       }

1801

1802       led->cdev.brightness = value;

1803       schedule_work(&led->work);

1804}

1730static void pm8xxx_led_work(struct work_struct *work)

1731{

1732       int rc;

1733

1734       struct pm8xxx_led_data *led = container_of(work,

1735                                                                       struct pm8xxx_led_data, work);

1736

1737       if (led->pwm_dev == NULL) {

1738                       __pm8xxx_led_work(led, led->cdev.brightness);

1739       } else {

1740                       rc = pm8xxx_led_pwm_work(led);

1741                       if (rc)

1742                                       pr_err("could not configure PWM mode for LED:%d\n",

1743                                                                                                                       led->id);

1744       }

1745}

對PM8XXX_ID_WLED，是使用__pm8xxx_led_work

1692static void __pm8xxx_led_work(struct pm8xxx_led_data *led,

1693                                                                       enum led_brightness level)

1694{

1695       int rc;

1696

1697       mutex_lock(&led->lock);

1698

1699       switch (led->id) {

1700       case PM8XXX_ID_LED_KB_LIGHT:

1701                       led_kp_set(led, level);

1702                       break;

1703       case PM8XXX_ID_LED_0:

1704       case PM8XXX_ID_LED_1:

1705       case PM8XXX_ID_LED_2:

1706                       led_lc_set(led, level);

1707                       break;

1708       case PM8XXX_ID_FLASH_LED_0:

1709       case PM8XXX_ID_FLASH_LED_1:

1710                       led_flash_set(led, level);

1711                       break;

1712      case PM8XXX_ID_WLED:

1713                      rc = led_wled_set(led, level);

1714                       if (rc < 0)

1715                                       pr_err("wled brightness set failed %d\n", rc);

1716                       break;

1717       case PM8XXX_ID_RGB_LED_RED:

1718       case PM8XXX_ID_RGB_LED_GREEN:

1719       case PM8XXX_ID_RGB_LED_BLUE:

1720                       led_rgb_set(led, level);

1721                       break;

1722       default:

1723                       dev_err(led->cdev.dev, "unknown led id %d", led->id);

1724                       break;

1725       }

1726

1727       mutex_unlock(&led->lock);

1728}

led_wled_set寫電源管理晶片pm8xxx的控制暫存器，控制wled。

Framebuffer fb_info::node

registered_fb它是一個數組，它的型別就是struct fb_info，它用於儲存我們呼叫register_framebuffer傳進來的struct fb_info。

num_registered_fb代表註冊幀緩衝裝置的個數。

   1522         for (i = 0; i < FB_MAX; i++)
   1523                 if (!registered_fb[i])
   1524                         break;
   1525         fb_info->node = i;

相當於找到一個空的次裝置號。

Framebuffer畫素格式

主屏Framebuffer格式 RGBA8888， config時指定；屏格式為RGB565或RGB888，由overlay pipe做轉換。

In mipi_dsi_probe()

481         /*

482         * get/set panel specific fb info

483         */

484         mfd->panel_info = pdata->panel_info;

485         pinfo = &mfd->panel_info;

486

487         if (mfd->panel_info.type == MIPI_VIDEO_PANEL)

488                         mfd->dest = DISPLAY_LCDC;

489         else

490                         mfd->dest = DISPLAY_LCD;

491

492         if (mdp_rev == MDP_REV_303 &&

493                         mipi_dsi_pdata->get_lane_config) {

494                         if (mipi_dsi_pdata->get_lane_config() != 2) {

495                                         pr_info("Changing to DSI Single Mode Configuration\n");

496#ifdef CONFIG_FB_MSM_MDP303

497                                         update_lane_config(pinfo);

498#endif

499                         }

500         }

501

502         if (mfd->index == 0)

503                         mfd->fb_imgType = MSMFB_DEFAULT_TYPE;   // configed as RGBA8888 for fb0

504         else

505                         mfd->fb_imgType = MDP_RGB_565;

msmfb_update_notify/ msmfb_no_update_notify

用於CABL功能時，統計直方圖使用；

更新螢幕前complete(&msmfb_update_notify)從而在準確時間點啟動直方圖統計；2*HZ後，msmfb_no_update_notify_timer超時，在timer超時回撥中complete(&mfd->msmfb_no_update_notify)結束直方圖統計。

sw_refresher

使用定時器去觸發mdp_refresh_screen，新增work進行dma_fnc呼叫。

針對某些介面的VIDEO模式屏且控制器沒有hw_refresh支援時，可以使用sw_refresher。

FB_ACTIVATE_VBL標誌涵義

fb_var_screeninfo結構體的成員變數activate的值設定FB_ACTIVATE_VBL，表示要等到下一個垂直同步事件出現時，再將當前要渲染的圖形緩衝區的內容繪製出來。這樣做的目的是避免出現螢幕閃爍，即避免前後兩個圖形緩衝區的內容各有一部分同時出現螢幕中。