linux-kernel - Re: [PATCH] arm64: dts: meson: fix g12a buses

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Message-ID: <61b854605207ee30969d25b1e16948e7a84d331a.camel@baylibre.com>
Date:   Fri, 18 Jan 2019 00:03:44 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, jianxin.pan@...ogic.com
Subject: Re: [PATCH] arm64: dts: meson: fix g12a buses

On Thu, 2019-01-17 at 23:42 +0100, Martin Blumenstingl wrote:
> On Thu, Jan 17, 2019 at 10:45 PM Jerome Brunet <jbrunet@...libre.com> wrote:
> > On Thu, 2019-01-17 at 22:20 +0100, Martin Blumenstingl wrote:
> > > On Thu, Jan 17, 2019 at 9:39 PM Jerome Brunet <jbrunet@...libre.com>
> > > wrote:
> > > > On Thu, 2019-01-17 at 21:27 +0100, Martin Blumenstingl wrote:
> > > > > OK, but we had incorrect documentation in the past. did you check
> > > > > this
> > > > > with someone from Amlogic?
> > > > > 
> > > > > I'm curious because there seem to be two different approaches here:
> > > > > 1) hiubus name and offsets are being fixed within this patch
> > > > > 2) aobus is being dropped here and re-introduced with a different
> > > > > name
> > > > > later
> > > > > on
> > > > > 
> > > > 
> > > > because hiu exist and aobus does not, for which both the name and size
> > > > was
> > > > wrong
> > > > 
> > > > > approach 1) can also be used for the "rti" region (at least in my
> > > > > opinion, the patch doesn't explain why it can't be done):
> > > > 
> > > > THe patch remove aobus (instead of fixing name and size) because, of
> > > > the
> > > > multiple region documented covered by this 'made region', I did not
> > > > anticipate
> > > > which one will be required and I did not want to add them all.
> > > > 
> > > > Better to add them as needed, which is want I done for pinctrl as you
> > > > pointed
> > > > out
> > > > 
> > > > > rename "aobus" to "rti" and change the size to either 0x1000 or
> > > > > 0xb000
> > > > > (both values can be found in mesong12a.dtsi from
> > > > > buildroot_openlinux_kernel_4.9_fbdev_20180706)
> > > > 
> > > > RTI is added here:
> > > > https://lkml.kernel.org/r/20190117103151.3349-1-jbrunet@baylibre.com
> > > > 
> > > > I don't really understand the problem ? result is the same
> > > the actual problem is "me" as I have conflicting information:
> > > - Amlogic's buildroot kernel (for G12A) uses similar bus definitions
> > > as the GX SoCs (for which there are public datasheets) - this is how
> > > Jianxin added it to meson-g12a.dtsi originally
> > 
> > And it was the same for the GX family. AOBUS in the DT while there nothing
> > about this in the memory map. Keep wrong patterns does not make them
> > right.
> > 
> > I'm merely reading the memory map here
> can you explain which "memory map" you are reading exactly?
> 
> my source is the "memory map" section in the public S905X and S912
> datasheets:
> - "S912_Datasheet_V0.220170314publicversion-Wesion.pdf" page 48
> - "S905X_Datasheet V0.3 20170314publicversion-Wesion.pdf" page 43

Those section yes

> 
> > > - this patch does it different - but cannot check if this is correct
> > > (no public datasheet is available for G12A or AXG) nor do I have a
> > > "big picture" of upcoming changes
> > 
> > Yes it does it differently. We should have picked up on this a while ago,
> > since gxbb at least, and we did not. There reason to create bus that don't
> > exist in the memory map of any recent SoC.
> in the GXL and GXM datasheets from above there is:
> range: 0xC8100000 - 0xC81FFFFF
> name: RTI

So we apparently agree that aobus does not exist

RTI simply goes fron 0xff800000 - 0xff800fff on the G12a doc, it is as simple
as that - as done in the pinctrl.

> 
> thus in my opinion, based on the two datasheets from above:
> - the bus definition (start, size) in meson-gx.dtsi is fine
> - probably have the wrong name for this bus in meson-gx.dtsi
> - (assuming that GXBB, GXL and GXM are all the same - I only compared
> the last two)

I still dont understand this focus on aobus which simply does not exist in the
map, whether it is by name of size or offset. Same goes cbus and apb.

> 
> > Creating bus should at least require a start and end offset explained
> > somewhere. Copying vendor DT is not enough
> I fully agree on this one!
> 
> 
> Regards
> Martin