[Qemu-devel] [Bug 1777672] [NEW] QEMU aarch64 virtual/physical frame buffer

* [Qemu-devel] [Bug 1777672] [NEW] QEMU aarch64 virtual/physical frame buffer
@ 2018-06-19 15:47 David Hoelzer
  2018-07-06 12:39 ` [Qemu-devel] [Bug 1777672] " Peter Maydell
                   ` (9 more replies)
  0 siblings, 10 replies; 11+ messages in thread
From: David Hoelzer @ 2018-06-19 15:47 UTC (permalink / raw)
  To: qemu-devel

Public bug reported:

I fully recognize that the error here could be mine, but the code is
pretty simple and straightforward; When emulating a Raspberry PI 3 using
aarch64 and allocating a virtual framebuffer larger than the physical
frambuffer (for double-buffering purposes), the QEMU window shows the
full size of the *virtual* framebuffer rather than the size of the
*physical* framebuffer.

You can replicate this with code such as:

#define FBWIDTH 1024
#define FBHEIGHT 768

void lfb_init()
{
    uart_puts("Initializing Framebuffer\n");
    mbox[0] = 35*4;
    mbox[1] = MBOX_REQUEST;

    mbox[2] = 0x48003;  //set phy wh
    mbox[3] = 8;
    mbox[4] = 8;
    mbox[5] = FBWIDTH;         //FrameBufferInfo.width
    mbox[6] = FBHEIGHT;          //FrameBufferInfo.height

    mbox[7] = 0x48004;  //set virt wh
    mbox[8] = 8;
    mbox[9] = 8;
    mbox[10] = FBWIDTH;        //FrameBufferInfo.virtual_width
    mbox[11] = FBHEIGHT * 2;         //FrameBufferInfo.virtual_height

    mbox[12] = 0x48009; //set virt offset
    mbox[13] = 8;
    mbox[14] = 8;
    mbox[15] = 0;           //FrameBufferInfo.x_offset
    mbox[16] = 0;           //FrameBufferInfo.y.offset

    mbox[17] = 0x48005; //set depth
    mbox[18] = 4;
    mbox[19] = 4;
    mbox[20] = 32;          //FrameBufferInfo.depth

    mbox[21] = 0x48006; //set pixel order
    mbox[22] = 4;
    mbox[23] = 4;
    mbox[24] = 1;           //RGB, not BGR preferably

    mbox[25] = 0x40001; //get framebuffer, gets alignment on request
    mbox[26] = 8;
    mbox[27] = 8;
    mbox[28] = 4096;        //FrameBufferInfo.pointer
    mbox[29] = 0;           //FrameBufferInfo.size

    mbox[30] = 0x40008; //get pitch
    mbox[31] = 4;
    mbox[32] = 4;
    mbox[33] = 0;           //FrameBufferInfo.pitch

    mbox[34] = MBOX_TAG_LAST;

    if(mbox_call(MBOX_CH_PROP) && mbox[20]==32 && mbox[28]!=0) {
        mbox[28]&=0x3FFFFFFF;
        fbwidth=mbox[5];
        fbheight=mbox[6];
        pitch=mbox[33];
        lfb=(void*)((unsigned long)mbox[28]);
    }
}

I will assume, for the sake of this posting, that the reader understands
the mailbox architecture and the appropriate address definitions for
them.  The key point is that allocating a virtual buffer twice the
height of the physical buffer results in QEMU improperly displaying a
double-height window.

** Affects: qemu
     Importance: Undecided
         Status: New

-- 
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devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1777672

Title:
  QEMU aarch64 virtual/physical frame buffer

Status in QEMU:
  New

Bug description:
  I fully recognize that the error here could be mine, but the code is
  pretty simple and straightforward; When emulating a Raspberry PI 3
  using aarch64 and allocating a virtual framebuffer larger than the
  physical frambuffer (for double-buffering purposes), the QEMU window
  shows the full size of the *virtual* framebuffer rather than the size
  of the *physical* framebuffer.

  You can replicate this with code such as:

  #define FBWIDTH 1024
  #define FBHEIGHT 768

  void lfb_init()
  {
      uart_puts("Initializing Framebuffer\n");
      mbox[0] = 35*4;
      mbox[1] = MBOX_REQUEST;

      mbox[2] = 0x48003;  //set phy wh
      mbox[3] = 8;
      mbox[4] = 8;
      mbox[5] = FBWIDTH;         //FrameBufferInfo.width
      mbox[6] = FBHEIGHT;          //FrameBufferInfo.height

      mbox[7] = 0x48004;  //set virt wh
      mbox[8] = 8;
      mbox[9] = 8;
      mbox[10] = FBWIDTH;        //FrameBufferInfo.virtual_width
      mbox[11] = FBHEIGHT * 2;         //FrameBufferInfo.virtual_height

      mbox[12] = 0x48009; //set virt offset
      mbox[13] = 8;
      mbox[14] = 8;
      mbox[15] = 0;           //FrameBufferInfo.x_offset
      mbox[16] = 0;           //FrameBufferInfo.y.offset

      mbox[17] = 0x48005; //set depth
      mbox[18] = 4;
      mbox[19] = 4;
      mbox[20] = 32;          //FrameBufferInfo.depth

      mbox[21] = 0x48006; //set pixel order
      mbox[22] = 4;
      mbox[23] = 4;
      mbox[24] = 1;           //RGB, not BGR preferably

      mbox[25] = 0x40001; //get framebuffer, gets alignment on request
      mbox[26] = 8;
      mbox[27] = 8;
      mbox[28] = 4096;        //FrameBufferInfo.pointer
      mbox[29] = 0;           //FrameBufferInfo.size

      mbox[30] = 0x40008; //get pitch
      mbox[31] = 4;
      mbox[32] = 4;
      mbox[33] = 0;           //FrameBufferInfo.pitch

      mbox[34] = MBOX_TAG_LAST;

      if(mbox_call(MBOX_CH_PROP) && mbox[20]==32 && mbox[28]!=0) {
          mbox[28]&=0x3FFFFFFF;
          fbwidth=mbox[5];
          fbheight=mbox[6];
          pitch=mbox[33];
          lfb=(void*)((unsigned long)mbox[28]);
      }
  }

  I will assume, for the sake of this posting, that the reader
  understands the mailbox architecture and the appropriate address
  definitions for them.  The key point is that allocating a virtual
  buffer twice the height of the physical buffer results in QEMU
  improperly displaying a double-height window.

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