Date: Thu, 8 Oct 2020 12:28:21 -0700 From: Mark Millard <marklmi@yahoo.com> To: Kyle Evans <kevans@freebsd.org> 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: <32A8A046-56DF-4998-9C3D-8630ACCE4951@yahoo.com> In-Reply-To: <CACNAnaFXpJcA5Xyw%2BPR6iem3U2nvpog53hsnCFKiGWiO6OgKKA@mail.gmail.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>
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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:
>>=20
>> On Thu, Oct 8, 2020 at 11:33 AM Kyle Evans <kevans@freebsd.org> =
wrote:
>>>=20
>>> On Thu, Oct 8, 2020 at 4:01 AM Mark Millard via freebsd-arm
>>> <freebsd-arm@freebsd.org> wrote:
>>>>=20
>>>> sys/gnu/dts/arm/bcm2711.dtsi reports:
>>>>=20
>>>> /*
>>>> * 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 ...]
>>>=20
>>> I have no words for how annoying this is.
>>>=20
>>=20
>> For a slightly more helpful response:
>>=20
>> 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.
>>=20
>> 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.
>>=20
>> =46rom my discussion (with an assist Ian on address interpretation) =
on
>> IRC, so I don't forget:
>>=20
>> 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 =3D <0x2>;
and the dma_addr and max_len by more local definitions,
such as in:
#address-cells =3D <0x1>;
#size-cells =3D <0x1>;
compatible =3D "simple-bus";
dma-ranges =3D <0xc0000000 0x0 0x0 0x40000000>;
and:
#address-cells =3D <0x2>;
#size-cells =3D <0x2>;
compatible =3D "simple-bus";
dma-ranges =3D <0x0 0x0 0x0 0x0 0x4 0x0>;
Note that the above has #size-cells varying when:
4 <=3D number of cells in dma-range . There will be
worse cases later, below.
and:
#address-cells =3D <0x3>;
#interrupt-cells =3D <0x1>;
#size-cells =3D <0x2>;
. . .
dma-ranges =3D <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 =3D <0x2>;
#size-cells =3D <0x1>;
compatible =3D "simple-bus";
dma-ranges =3D <0x0 0xc0000000 0x0 0x0 0x40000000>;
and:
#address-cells =3D <0x1>;
#size-cells =3D <0x2>;
compatible =3D "simple-bus";
dma-ranges =3D <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.
>>=20
>> 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)
>>=20
>> This won't match perfectly with what we currently return, but it will
>> be more accurate.
>=20
> 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).
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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