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Subject: Re: BOG: commit 89c7cb1608ac3 ("of/device: Update dma_range_map only when dev has valid dma-ranges") seems to break Pinephone display or LCDC
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From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <YBkh6IZfmzaLWYPp@aptenodytes>
Date:   Tue, 2 Feb 2021 11:50:48 +0100
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Yong Wu <yong.wu@mediatek.com>, Rob Herring <robh@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>
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Message-Id: <E45AE13E-6A74-43E6-A7AE-B0D425B10344@goldelico.com>
References: <81FE44A3-38C8-4B78-BB77-C09B4FC80B0A@goldelico.com> <YBkh6IZfmzaLWYPp@aptenodytes>
To:     Paul Kocialkowski <paul.kocialkowski@bootlin.com>
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Hi Paul,

> Am 02.02.2021 um 10:56 schrieb Paul Kocialkowski =
<paul.kocialkowski@bootlin.com>:
>=20
> Hi Nikolaus,
>=20
> On Tue 02 Feb 21, 10:18, H. Nikolaus Schaller wrote:
>> Hi,
>> since v5.11-rc6 my Pinephone display shows some moir=C3=A9 pattern.
>>=20
>> I did a bisect between v5.11-rc5 and v5.11-rc6 and it told me that
>> the commit mentioned in the subject is the reason.
>>=20
>> Reverting it makes the display work again and re-reverting fail =
again.
>>=20
>> IMHO it seems as if the display DMA of the pinephone (allwinner =
suni-a54)
>> got influenced and stopped to scan the framebuffer.
>>=20
>> The only dma-ranges I could find are defined here:
>>=20
>> 	arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
>>=20
>> 	dma-ranges =3D <0x00000000 0x40000000 0xc0000000>;
>>=20
>> but I can't tell if they are "valid" or not.
>>=20
>> Any insights are welcome. And please direct to the right =
people/mailing lists
>> if they are missing.
>=20
> This may not be strictly the same thing, but is this patch in your =
tree:
> =
https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210115175831=
.1184260-2-paul.kocialkowski@bootlin.com/
>=20
> If not, it's worth a try to add it.

No, it hasn't arrived in v5.11-rc6 (or linux-next) yet.

But it fixes the issue.

great and many thanks,
Nikolaus

> If it is, it's worth doing a revert.
>=20
> My understanding is like DE2 does not need a particular DMA range and =
has DRAM
> starting at 0x40000000 (just like the CPU) but it will map DRAM in a =
loop
> before and after this address.
>=20
> I suspect the issue shows because the pinephone has 2 GiB RAM while =
for other
> boards with < 2 GiB RAM, removing 0x40000000 to the DMA addresses =
still points
> to the same location. So IMO the MBUS dma-ranges shouldn't apply to =
DE2.
> I think this is already the case in dt, but the mbus driver may add it =
if you
> don't have that patch.
>=20
> I think I have a few A64 boards around, but probably not with 2 GiB =
RAM.
> If adding the patch doesn't help, I'll try to make a few test.
>=20
> Cheers!
>=20
> Paul
>=20
> --=20
> Paul Kocialkowski, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com