Date: Mon, 26 Nov 2012 07:05:37 -0800 From: Tim Kientzle <kientzle@freebsd.org> To: Oleksandr Tymoshenko <gonzo@bluezbox.com> Cc: FreeBSD Hackers <hackers@freebsd.org>, Alexander Yerenkow <yerenkow@gmail.com> Subject: Re: FreeBSD on RaspberryPi Message-ID: <1E75CEAC-32E8-4048-A1FB-DD59F996E22F@freebsd.org> In-Reply-To: <C706651B-ABBE-4CEC-96D9-A5214BFEC11D@bluezbox.com> References: <31C904E6-F230-4187-AE32-F9A7B1A7C38E@freebsd.org> <CAPJF9w=-pgVsz3JkKcwq7ZRYUNKUdFdEvU0fZZzZrVxTRpLW3w@mail.gmail.com> <4A5E03E5-3295-4FD4-9A06-7D1C4E9E0C12@freebsd.org> <CAPJF9wk%2B_5F4PAu8bK6A=Lfup6Qi_5OUJOqWfcJRKLJmeGSqGg@mail.gmail.com> <B11C8BD8-1F6B-4300-9BC9-77CD81F9670E@freebsd.org> <CAPJF9wnk6qqAA3F69CokRrHOsAotbUDtQPOiZ=EuhO7ZfM2y0Q@mail.gmail.com> <EFED5426-7DF7-41DA-82B1-6FEAB21EA098@freebsd.org> <9E4DA920-BE72-4AA0-8159-43205CDEF5CD@bluezbox.com> <EBE2570F-E57F-42F7-A7A5-5291E8CD81F1@freebsd.org> <C706651B-ABBE-4CEC-96D9-A5214BFEC11D@bluezbox.com>
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On Nov 25, 2012, at 11:46 PM, Oleksandr Tymoshenko wrote: >=20 > On 2012-11-25, at 9:32 AM, Tim Kientzle <kientzle@freebsd.org> wrote: >=20 >>=20 >> On Nov 24, 2012, at 8:01 PM, Oleksandr Tymoshenko wrote: >>=20 >>>=20 >>> On 2012-11-24, at 4:47 PM, Tim Kientzle <kientzle@freebsd.org> = wrote: >>>=20 >>>=20 >=20 > .. skipped .. >=20 >>> Tim, >>>=20 >>> I'm almost done with getting kernel working with latest raspberry Pi = firmware. Just need >>> to figure out how to make ubldr pass FDT pointer from u-boot to = kernel and handle=20 >>> /reserve/ information in ARM machdep code.=20 >>=20 >> Let me know if you need help with this. I've worked with >> the ubldr FDT code recently. >>=20 >>> Meanwhile I suggest editing .dts file manually. Fill out "display" = node properties with proper >>> display resolution and depth. Also add ukbd driver. That should get = you working console. >>=20 >> I'll try that. >>=20 >> I'm curious: why is this information coming from the DTS? >> That seems pretty complex; I thought that the >> console code would query this information via the mailbox >> interface. >=20 >=20 > It's either FDT blob or message box interface. Implementation = complexity is about the same. My thinking: * Display resolution used by kernel has to match what the firmware = uses. So the kernel should either get the information from the firmware = or from the same place the firmware gets it from. * We want ubldr to remain generic, so I'm reluctant to put things into = it that are RaspberryPi-specific. If the firmware is putting the values into the FDT, then having the = kernel get it from the FDT is another way for the kernel to get it from = the firmware, so that sounds okay. > But since we're getting other variables (like MAC address, memory = size) from FDT I decided > to be consistent and get all of them from there. I don't know about MAC address. Memory size is handled generically by = ubldr using a standard interface to U-Boot, so it's not special to = RaspberryPi. The FDT editing is just a standard way for ubldr to pass = this to the kernel. > The issue I'm facing is that ubldr gets FDT blob > either from file directly or from ELF kernel itself. While on = Raspberry Pi to works as follows: >=20 > - Firmware loads .dtb file from SD card to specified address Does RaspberryPi firmware now load an FDT? Does the firmware now read the FDT to get its values for display = resolution, etc? (I don't really like this because a lot of people need to tweak the = display settings and it's hard to tell a 6-year-old how to edit and = recompile an FDT.) > - Fixes up values like amount of memory, reserved regions, UART and = clock frequencies,=20 > MAC address, display resolution. > - Passes control to next link in boot chain (e.g. U-Boot) To be clear: You say the RPi firmware is already doing this editing? So the ubldr just has to pass the RPi FDT to the kernel? If so, that's = a lot simpler. > I'm thinking about adding compile-time constant FDT_BLOB_ADDRESS and = arrange possible > FDT sources in following priority: >=20 > - Check FDT_BLOB_ADDRESS (if defined) > - Check dtb file > - Check ELF kernel >=20 > Does it sound sane enough?=20 If the RPi firmware always loads the FDT at a fixed address and the RPi firmware is using the FDT to configure itself, then it makes a lot of sense. It would be nice to do this without adding RPi-specific code to ubldr. > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to = "freebsd-hackers-unsubscribe@freebsd.org" >=20
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