Date: Thu, 8 Oct 2020 14:32:09 -0500 From: Kyle Evans <kevans@freebsd.org> To: Mark Millard <marklmi@yahoo.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: RPi4B: emmc2bus dma-range handling does not track the boot-time-FDT (u-boot based booting) Message-ID: <CACNAnaHwAyw=6tiOC12WH9BBcj5FDZzDGxoh0UJw9KL0HE206g@mail.gmail.com> In-Reply-To: <32A8A046-56DF-4998-9C3D-8630ACCE4951@yahoo.com> References: <D8BDF95A-D6A8-4E95-A0CE-D53068E8355B.ref@yahoo.com> <D8BDF95A-D6A8-4E95-A0CE-D53068E8355B@yahoo.com> <CACNAnaG3CKTiXdXNUO1Jgr34=XGF4wYRuUnuiJRhNb1J9XaGbw@mail.gmail.com> <CACNAnaEZP=Gxs4cbvCOFzM8MZB6-2Ny0N7KEW-nYoDw22_Jzwg@mail.gmail.com> <CACNAnaFXpJcA5Xyw%2BPR6iem3U2nvpog53hsnCFKiGWiO6OgKKA@mail.gmail.com> <32A8A046-56DF-4998-9C3D-8630ACCE4951@yahoo.com>
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On Thu, Oct 8, 2020 at 2:28 PM Mark Millard <marklmi@yahoo.com> wrote:
>
>
>
> On 2020-Oct-8, at 11:34, Kyle Evans <kevans at freebsd.org> wrote:
>
> > On Thu, Oct 8, 2020 at 12:38 PM Kyle Evans <kevans@freebsd.org> wrote:
> >>
> >> On Thu, Oct 8, 2020 at 11:33 AM Kyle Evans <kevans@freebsd.org> wrote:
> >>>
> >>> On Thu, Oct 8, 2020 at 4:01 AM Mark Millard via freebsd-arm
> >>> <freebsd-arm@freebsd.org> wrote:
> >>>>
> >>>> sys/gnu/dts/arm/bcm2711.dtsi reports:
> >>>>
> >>>> /*
> >>>> * emmc2 has different DMA constraints based on SoC revisions. It was
> >>>> * moved into its own bus, so as for RPi4's firmware to update them.
> >>>> * The firmware will find whether the emmc2bus alias is defined, and if
> >>>> * so, it'll edit the dma-ranges property below accordingly.
> >>>> */
> >>>> [... snip ...]
> >>>
> >>> I have no words for how annoying this is.
> >>>
> >>
> >> For a slightly more helpful response:
> >>
> >> We can fix this, and it ends up being much cleaner than my current
> >> hack. Basically, in bcm2835_vcbus.c, we should eradicate the
> >> busdma_lowaddr from bcm283x_memory_soc_cfg.
> >>
> >> bcm283x_dmabus_peripheral_lowaddr should instead take a device_t and
> >> grab the bus's dma-ranges. It /looks/ to be valid on all the DTS I see
> >> for the RPi boards we support, so we can just unconditionally use that
> >> and things will just work for the newer RPi4 models.
> >>
> >> From my discussion (with an assist Ian on address interpretation) on
> >> IRC, so I don't forget:
> >>
> >> dma-ranges is three-value: <dma_addr cpu_addr max_len>
>
> Note: For the below I looked at 3 separate RPi4B
> examples, using u-boot print fdt / when I could
> or translating the dtb to a dts otherwise. One
> of the examples is from one of ubuntu 2020.04.1's
> RPi4B specific builds. The others I use with FreeBSD,
> one for u-boot and one for uefi/ACPI.
>
> (
>
> cpu_addr is sized via the global:
>
> / {
>
> #address-cells = <0x2>;
>
> and the dma_addr and max_len by more local definitions,
> such as in:
>
> #address-cells = <0x1>;
> #size-cells = <0x1>;
> compatible = "simple-bus";
> dma-ranges = <0xc0000000 0x0 0x0 0x40000000>;
>
> and:
>
> #address-cells = <0x2>;
> #size-cells = <0x2>;
> compatible = "simple-bus";
> dma-ranges = <0x0 0x0 0x0 0x0 0x4 0x0>;
>
> Note that the above has #size-cells varying when:
> 4 <= number of cells in dma-range . There will be
> worse cases later, below.
>
> and:
>
> #address-cells = <0x3>;
> #interrupt-cells = <0x1>;
> #size-cells = <0x2>;
> . . .
> dma-ranges = <0x2000000 0x0 0x0 0x0 0x0 0x0 0xc0000000>;
>
> (The #address-cells being 3 indicates a bit mask as the first of the 3,
> the bit mask indicating extra information about the context.)
>
> and:
>
> #address-cells = <0x2>;
> #size-cells = <0x1>;
> compatible = "simple-bus";
> dma-ranges = <0x0 0xc0000000 0x0 0x0 0x40000000>;
>
> and:
>
> #address-cells = <0x1>;
> #size-cells = <0x2>;
> compatible = "simple-bus";
> dma-ranges = <0x0 0x0 0x0 0x4 0x0>;
>
> Note that for the last 2 examples above the number of cells
> in the dma-range (5) is not sufficient to indicate the value
> for #size-cells or #(dma-addr-cells) without presuming some
> other context to disambiguate.
>
>
> There is also an example of just:
>
> dma-ranges;
>
> (in firmware { . . . }).
>
> >> We'll see 4 and 5 value variants of this because 64-bit addresses are
> >> described with pairs of 32-bit values.
> >>
> >> 4-value variant: dma_addr will be 32-bit, cpu_addr will be 64-bit
> >> 5-value variant: both are 64-bit
>
> There is an example shown above with 5-value having #size_cells
> being 1 (32-bit) [and dma-addr being 64 bit (cells 2)] instead of
> #size_cells being 2 (64-bit) [and dma_addr being 32-bit (cells 1)].
>
> >> Note that bcm283x_dmabus_peripheral_lowaddr() will be returning
> >> cpu_addr + (max_len - 1)
> >>
> >> This won't match perfectly with what we currently return, but it will
> >> be more accurate.
> >
> > Here's a patch that I hacked out and can't test for quite a while yet,
> > feel free to give it a shot:
> > https://people.freebsd.org/~kevans/bcm2835_vcbus.diff -- the best
> > guarantee I can give you is that it builds. We'll need to test it on
> > both RPi4 models with the separate bus and the original RPi4s, as well
> > as an RPi3 and RPi2/0w.
>
> See above about trying to use the number of cells in a dma-ranges
> to figure out the sizes of #size-cells or #(dma-addr-cells).
>
Yeah, Ian pointed out just a little bit ago the way this should be
done correctly. The hacky patch should at least get it correct enough
for now, then I can write a more generic version of dma-ranges parsing
that does it correctly.
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