mx51的三个framebuffer,mxc_ipuv3_fb.c分析

mx51支持三个framebuffer:fb0, fb1, fb2

/dev/graphics/fb0,/dev/graphics/fb1:

一个作为系统的主framebuffer,另外一个作为TVOUT输出的framebuffer,缺省情况下,fb0做primary(也就是用来在primary LCD显示UI),fb1做secondary(也就是用来在TVOUT输出上显示数据)。

根据项目中的实际物理连接情况,如果primary LCD连接到disp0,那么使用缺省设置,如果primary LCD连接到disp1,那么就要在kernel启动参数中加入di1_primary。

/dev/graphics/fb2 :

用来实现overlay叠加,显示video数据的framebuffer,仅支持bpp16,数据格式是yuv422,可以在DP(Display Process)和来自MEM_BG_SYNC的数据进行合成,再传送到DC/DI。


在mxc framebuffer probe 时,第一个注册的mxc framebuffer (fb0 或者fb1,这个framebuffer作为主LCD的framebuffer)使用MEM_BG_SYNC,第二个注册的mxc framebuffer(fb0或者fb1,这个framebuffer作为TVOUT使用的framebuffer)使用MEM_DC_SYNC,最后一个注册的framebuffer(fb2)使用MEM_FG_SYNC。


MEM_BG_SYNC 和MEM_FG_SYNC都是mx5x ipu中独一无二的资源,这意味着每个通道只能被其中一个framebuffer占用。事实上MEM_DC_SYNC这个通道并不存在,只是用来表示直接连接到DC


注意这几个framebuffer中的数据并不是直连显示设备,中间可能还有MX51 IPU的DP处理单元,DP Unit负责对fb0 fb1 fb2过来的数据进行处理,包括颜色转换,图层合并,gamma处理以及光标处理后发送给DC->DI->显示设备

fsl 在/sys/class/graphics/fbx/ 下创建了一个fsl特定的属性文件fsl_disp_property,在我的机器上显示如下

# cat /sys/class/graphics/fb0/fsl_disp_property
2-layer-fb-bg
# cat /sys/class/graphics/fb1/fsl_disp_property
1-layer-fb
# cat /sys/class/graphics/fb2/fsl_disp_property
2-layer-fb-fg


2-layer-fb-bg,表示fb0使用MEM_BG_SYNC通道,在IPU 的Display Process模块和MEM_FG_SYNC通道来的数据合并,再送入DC

1-layer-fb,表示fb1使用MEM_DC_SYNC通道,不经过Display Process模块,DC(Display Control)直接连接到DI(Display Interface)

2-layber-fb-fg,表示fb2使用MEM_FG_SYNC通道,在IPU的Display Process模块和MEM_BG_SYNC通道来的数据合并,再送入DC

应用层还可以修改/sys/class/graphics/fb0/fsl_disp_property和/sys/class/graphics/fb1/fsl_disp_property,使用如下命令:

echo 1-layer-fb > /sys/class/graphics/fb0/fsl_disp_property
或者

echo 2-layer-fb-bg > /sys/class/graphics/fb1/fsl_disp_property

注意,二者的作用是一样的,都会导致fb0和fb1交换显示通道,fsl引入这个属性的目的,就是给上层应用提供一个接口,使得应用层可以控制fb0 fb1使用MEM_BG_SYNC还是MEM_DC_SYNC通道,说到这里可能还是让人糊涂,为什么应用层要选择fb0 fb1的通道,这要先搞清楚MEM_BG_SYNC和MEM_DC_SYNC的区别。

imx51/imx53 IPU支持三种类型的显示通道:MEM_BG_SYNC, MEM_FG_SYNC和MEM_DC_SYNC,framebuffer只能通过三者之一传送数据,这些通道在物理上是唯一的,同一时间只能被一个framebuffer使用。

MEM_BG_SYNC:fb0 -> DP (full plane) -> DC -> DI0
MEM_FG_SYNC:fb2 -> DP (partial plane) -> DC -> DI0
MEM_DC_SYNC:fb1 -> DC -> DI1

MEM_BG_SYNC和MEM_FG_SYNC会在DP进行合并处理,这个功能就是所谓的overlay。

正常情况下来自fb0的UI和来自fb2的video数据在DP合并后,送到DI0,我们就可以看到UI 浮在video上面的效果。但是当激活双屏的时候,一般希望video数据和UI 都送到后屏(也就是DI1),前屏只显示UI。这就需要fb1拥有MEM_BG_SYNC,此时需要交换fb1和fb0的显示通道如下:

MEM_BG_SYNC: fb1 -> DP (full plane) -> DC -> DI0
MEM_FG_SYNC: fb2 -> DP (partial plane) -> DC -> DI1
MEM_DC_SYNC: fb0 -> DC -> DI0

通道交换代码

swap_disp_chan

1673 static ssize_t swap_disp_chan(struct device *dev,
1674                   struct device_attribute *attr,
1675                   const char *buf, size_t count)
1676 {
1677     struct fb_info *info = dev_get_drvdata(dev);
1678     struct mxcfb_info *mxcfbi = (struct mxcfb_info *)info->par;
1679     struct mxcfb_info *fg_mxcfbi = NULL;
1680 
1681     acquire_console_sem();
1682     /* swap only happen between DP-BG and DC, while DP-FG disable */
1683     if (((mxcfbi->ipu_ch == MEM_BG_SYNC) &&
1684          (strstr(buf, "1-layer-fb") != NULL)) ||
1685         ((mxcfbi->ipu_ch == MEM_DC_SYNC) &&
1686          (strstr(buf, "2-layer-fb-bg") != NULL))) {
1687         int i;
1688 
1689         for (i = 0; i < num_registered_fb; i++) {
1690             fg_mxcfbi =
1691                 (struct mxcfb_info *)mxcfb_info[i]->par;
1692             if (fg_mxcfbi->ipu_ch == MEM_FG_SYNC)
1693                 break;
1694             else
1695                 fg_mxcfbi = NULL;
1696         }
1697         if (!fg_mxcfbi ||
1698             fg_mxcfbi->cur_blank == FB_BLANK_UNBLANK) {
1699             dev_err(dev,
1700                 "Can not switch while fb2(fb-fg) is on.\n");
1701             release_console_sem();
1702             return count;
1703         }
1704 
1705         if (swap_channels(info) < 0)
1706             dev_err(dev, "Swap display channel failed.\n");
1707     }
1708 
1709     release_console_sem();
1710     return count;
1711 }
1712 DEVICE_ATTR(fsl_disp_property, 644, show_disp_chan, swap_disp_chan);

1682~1686 只有fb0和fb1才会参与显示通道的交换,fb2只使用MEM_FG_SYNC
1705 调用swap_channels实现通道的切换

swap_channels

 545 static int swap_channels(struct fb_info *fbi)
 546 {
 547     int i;
 548     int swap_mode;
 549     ipu_channel_t ch_to;
 550     struct mxcfb_info *mxc_fbi_from = (struct mxcfb_info *)fbi->par;
 551     struct fb_info *fbi_to = NULL;
 552     struct mxcfb_info *mxc_fbi_to;
 553 
 554     /* what's the target channel? */
 555     if (mxc_fbi_from->ipu_ch == MEM_BG_SYNC)
 556         ch_to = MEM_DC_SYNC;
 557     else
 558         ch_to = MEM_BG_SYNC;
 559 
 560     for (i = 0; i < num_registered_fb; i++) {
 561         mxc_fbi_to =
 562             (struct mxcfb_info *)mxcfb_info[i]->par;
 563         if (mxc_fbi_to->ipu_ch == ch_to) {
 564             fbi_to = mxcfb_info[i];
 565             break;
 566         }
 567     }
 568     if (fbi_to == NULL)
 569         return -1;
 570 
 571     ipu_clear_irq(mxc_fbi_from->ipu_ch_irq);
 572     ipu_clear_irq(mxc_fbi_to->ipu_ch_irq);
 573     ipu_free_irq(mxc_fbi_from->ipu_ch_irq, fbi);
 574     ipu_free_irq(mxc_fbi_to->ipu_ch_irq, fbi_to);
 575 
 576     if (mxc_fbi_from->cur_blank == FB_BLANK_UNBLANK) {
 577         if (mxc_fbi_to->cur_blank == FB_BLANK_UNBLANK)
 578             swap_mode = BOTH_ON;
 579         else
 580             swap_mode = SRC_ON;
 581     } else {
 582         if (mxc_fbi_to->cur_blank == FB_BLANK_UNBLANK)
 583             swap_mode = TGT_ON;
 584         else
 585             swap_mode = BOTH_OFF;
 586     }
 587 
 588     /* tvout di-1: for DC use UYVY, for DP use RGB */
 589     if (mxc_fbi_from->ipu_di == 1 && ch_to == MEM_DC_SYNC) {
 590         fbi->var.bits_per_pixel = 16;
 591         fbi->var.nonstd = IPU_PIX_FMT_UYVY;
 592     } else if (mxc_fbi_from->ipu_di == 1 && ch_to == MEM_BG_SYNC) {
 593         fbi->var.nonstd = 0;
 594     } else if (mxc_fbi_from->ipu_di == 0 && ch_to == MEM_DC_SYNC) {
 595         fbi_to->var.nonstd = 0;
 596     } else if (mxc_fbi_from->ipu_di == 0 && ch_to == MEM_BG_SYNC) {
 597         fbi->var.bits_per_pixel = 16;
 598         fbi->var.nonstd = IPU_PIX_FMT_UYVY;
 599     }
 600 
 601     switch (swap_mode) {
 602     case BOTH_ON:
 603         /* disable target->switch src->enable target */
 604         _swap_channels(fbi, fbi_to, true);
 605         break;
 606     case SRC_ON:
 607         /* just switch src */
 608         _swap_channels(fbi, fbi_to, false);
 609         break;
 610     case TGT_ON:
 611         /* just switch target */
 612         _swap_channels(fbi_to, fbi, false);
 613         break;
 614     case BOTH_OFF:
 615         /* switch directly, no more need to do */
 616         mxc_fbi_to->ipu_ch = mxc_fbi_from->ipu_ch;
 617         mxc_fbi_from->ipu_ch = ch_to;
 618         i = mxc_fbi_from->ipu_ch_irq;
 619         mxc_fbi_from->ipu_ch_irq = mxc_fbi_to->ipu_ch_irq;
 620         mxc_fbi_to->ipu_ch_irq = i;
 621         break;
 622     default:
 623         break;
 624     }
 625 
 626     if (ipu_request_irq(mxc_fbi_from->ipu_ch_irq, mxcfb_irq_handler, 0,
 627         MXCFB_NAME, fbi) != 0) {
 628         dev_err(fbi->device, "Error registering irq %d\n",
 629             mxc_fbi_from->ipu_ch_irq);
 630         return -EBUSY;
 631     }
 632     ipu_disable_irq(mxc_fbi_from->ipu_ch_irq);
 633     if (ipu_request_irq(mxc_fbi_to->ipu_ch_irq, mxcfb_irq_handler, 0,
 634         MXCFB_NAME, fbi_to) != 0) {
 635         dev_err(fbi_to->device, "Error registering irq %d\n",
 636             mxc_fbi_to->ipu_ch_irq);
 637         return -EBUSY;
 638     }
 639     ipu_disable_irq(mxc_fbi_to->ipu_ch_irq);
 640 
 641     return 0;
 642 } 

550 mxc_fbi_from 和字面意思一样,我们想要交换哪一个fb_info,也就是交换源

555~558 交换只发生在MEM_DC_SYNC和MEM_BG_SYNC之间,如果源fb的通道是MEM_BG_SYNC,那么我们希望交换为MEM_DC_SYNC,反之亦然。

560~567 找到目标通道坐在的framebuffer

576~586 swap_mode记录下source和dest framebuffer的blank状态

571~574 先释放from和to的ipu 通道中断号,因为IPU通道中断号也会随着通道一起交换

589~599 I have no idea

601~613 _swap_channels进行交换

614~620 如果fbi_from和fbi_to都处于BLANK状态,那么直接交换通道即可,注意通道中断号也需要交换,因为通道和通道中断号是一一对应的。

626~642 重新为fbi_from和fbi_to申请ipu irq,这里disable了irq,不过不要紧,当pan_display操作时,会使能ipu irq

swap_channels

 504 static int _swap_channels(struct fb_info *fbi,
 505               struct fb_info *fbi_to, bool both_on)
 506 {
 507     int retval, tmp;
 508     ipu_channel_t old_ch;
 509     struct mxcfb_info *mxc_fbi_from = (struct mxcfb_info *)fbi->par;
 510     struct mxcfb_info *mxc_fbi_to = (struct mxcfb_info *)fbi_to->par;
 511 
 512     if (both_on) {
 513         ipu_disable_channel(mxc_fbi_to->ipu_ch, true);
 514         ipu_uninit_channel(mxc_fbi_to->ipu_ch);
 515     }
 516 
 517     /* switch the mxc fbi parameters */
 518     old_ch = mxc_fbi_from->ipu_ch;
 519     mxc_fbi_from->ipu_ch = mxc_fbi_to->ipu_ch;
 520     mxc_fbi_to->ipu_ch = old_ch;
 521     tmp = mxc_fbi_from->ipu_ch_irq;
 522     mxc_fbi_from->ipu_ch_irq = mxc_fbi_to->ipu_ch_irq;
 523     mxc_fbi_to->ipu_ch_irq = tmp;
 524 
 525     _setup_disp_channel1(fbi);
 526     retval = _setup_disp_channel2(fbi);
 527     if (retval)
 528         return retval;
 529 
 530     /* switch between dp and dc, disable old idmac, enable new idmac */
 531     retval = ipu_swap_channel(old_ch, mxc_fbi_from->ipu_ch);
 532     ipu_uninit_channel(old_ch);
 533 
 534     if (both_on) {
 535         _setup_disp_channel1(fbi_to);
 536         retval = _setup_disp_channel2(fbi_to);
 537         if (retval)
 538             return retval;
 539         ipu_enable_channel(mxc_fbi_to->ipu_ch);
 540     }
 541 
 542     return retval;
 543 }

504~505 函数有三个参数,@fbi是source,@fbi_to是dest,@both_on 布尔量为true 则@fbi_to为UNBLANK状态;false,则@fbi_to为BLANK状态。这里@fbi一定为UNBLANK状态,否则不会调用这个函数。

512~515 在交换之前,先销毁掉@fbi_to的channel

518~523 交换二者的通道和通道irq

525~528 交换完成后,设置disp通道的参数。

531~532 现在,通道号已经交换完成,但是还有一件事没有完成,我们知道DC通道1,5的控制寄存器DC_WR_CH_CONF_x中,配置着这个DC通道连接到哪一个DI,我们希望交换通道,但是不希望更改到DI的配置。ipu_swap_channel交换两个DC通道的DI配置。









   

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