On Mon, Jul 13, 2015 at 12:17 PM, 桥 杨 <yangqiao0...@me.com> wrote: > > >> 在 2015年7月13日，17:40，Gedare Bloom <ged...@rtems.org> 写道： >> >>> On Sat, Jul 11, 2015 at 11:29 AM, QIAO YANG <yangqiao0...@me.com> wrote: >>> Hi, >>> >>> I tried to retrieve atag command lines but I've got wired problems: >>> I ran a quick scan for atags, start from 0x100, and I've got an output like >>> : >>> >>> [ATAG_CORE] flags: 0, pagesize: 0, rootdev: 0 >>> [ATAG_MEM] size: 8000000, start: 0 >>> [ATAG_CMDLINE] found: >>> dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 >>> bcm2708.boardrev=0xf bcm2708.serial=0x8247b4bb smsc95xx.macaddr=B8s >>> start addr:12C >>> size : 2E616D64 >>> didn't find [ATAG_NONE] >>> >>> which told me that: >>> 1. The start address of atag cmdline is 0x12C >>> 2. The size of this tag is 0x2E616D64 >>> The size of the tag is abnormal. >>> From the output, it seems that I only retrieved part of the cmdline. >> Perhaps you have messed up the field layout or somehow gotten the >> wrong field offsets? > > I've verified that. > > >> >>> >>> I've also tried to use the mailbox interface to get the cmdline. what I've >>> got is exactly the same part of string without error reponse. Even if I >>> tried to print the following characters, they are all empty. >>> I think that the atags area maybe rewritten in some way but I didn't managed >>> to figure out. What bothers me most is the length of the tag, because the >>> tag id is correct, part of the value is readable, there's no reason that the >>> data between them is incorrect. The atag area should be written by >>> videocore, who load the cmdline.txt where we can add additional lines. >>> >>> >>> Besides I've also got a question that how can I get the value of r2 that >>> passed by bootloader to kernel image? It should store the value of start >>> address of ATAG or the magic of device tree. What I've found in linux is >>> that there is a function like init( *param), which is called when loading >>> the kernel, and the function get the value of r2 as the parameter passed to >>> it. I wonder how can I get this value, though by default the atag starts >>> from 0x100. >> Check in the BSP boot-up code (usually in the bsp subdirectory, start.S >> file). > > I've found it. It use the default startup code. Is there a possibility that > the default arm start.S messed up something? This might also explain why it > bugged when using uboot to load it? > The default may not preserve the r2 register?
>> >>> >>> If it takes too long to implement the feature (atag, device tree ....), I've >>> got other ways to detect if a hdmi device is present and then disable/enable >>> the graphic console. If I'm allowed to pass the atag/device tree >>> implementation. >> Can you clarify this statement? What "other ways" do you mean? >> > > If no display is connected , when we query the display size , vc will return > 656*416. I'm not sure if it's acceptable to be used as a probe. > If the return value without a display is a constant value, then this should be ok to use temporarily at least. But you should continue to work on getting the atag/dt working correctly, while you can work on other parts of your project in parallel (Porting the graphics toolkit to RSB). > >>> >>> Best wishes. >>> >>> _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
