[PATCH v1 00/15] add basic driver support for broadcom NS3 soc

Fri Jun 5 20:22:16 CEST 2020

On Fri, Jun 05, 2020 at 12:47:10PM -0300, Walter Lozano wrote:
> Hi Tom,
> 
> On 5/6/20 12:05, Tom Rini wrote:
> > On Fri, Jun 05, 2020 at 11:36:57AM +0200, Soeren Moch wrote:
> > > On 04.06.20 05:16, Tom Rini wrote:
> > > > On Wed, Jun 03, 2020 at 08:59:58PM -0600, Simon Glass wrote:
> > > > > Hi Rayagonda,
> > > > > 
> > > > > On Wed, 3 Jun 2020 at 03:10, Rayagonda Kokatanur
> > > > > <rayagonda.kokatanur at broadcom.com> wrote:
> > > > > > Hi Simon,
> > > > > > 
> > > > > > On Wed, May 20, 2020 at 7:50 PM Simon Glass <sjg at chromium.org> wrote:
> > > > > > > Hi Rayagonda,
> > > > > > > 
> > > > > > > On Tue, 19 May 2020 at 23:19, Rayagonda Kokatanur
> > > > > > > <rayagonda.kokatanur at broadcom.com> wrote:
> > > > > > > > Hi Thomas,
> > > > > > > > 
> > > > > > > > On Wed, May 20, 2020 at 7:34 AM Thomas Fitzsimmons <fitzsim at fitzsim.org> wrote:
> > > > > > > > > Rayagonda Kokatanur <rayagonda.kokatanur at broadcom.com> writes:
> > > > > > > > > 
> > > > > > > > > > On Tue, May 19, 2020 at 11:01 PM Tom Rini <trini at konsulko.com> wrote:
> > > > > > > > > > > On Tue, May 19, 2020 at 10:39:49PM +0530, Rayagonda Kokatanur wrote:
> > > > > > > > > > > > Hi Tom,
> > > > > > > > > > > > 
> > > > > > > > > > > > 
> > > > > > > > > > > > On Tue, May 19, 2020 at 12:46 AM Tom Rini <trini at konsulko.com> wrote:
> > > > > > > > > > > > > On Sun, May 17, 2020 at 01:49:30PM +0530, Rayagonda Kokatanur wrote:
> > > > > > > > > > > > > 
> > > > > > > > > > > > > > This is the second patch set series prepared on top of the
> > > > > > > > > > > > > > first patch set ("add initial support for broadcom NS3 soc").
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > This patch set will add following,
> > > > > > > > > > > > > > -dt nodes and defconfig options for basic device like pinctrl,
> > > > > > > > > > > > > >   gpio, mmc, qspi, wdt, i2c and pcie.
> > > > > > > > > > > > > > -start wdt service
> > > > > > > > > > > > > > -Enable GPT commands
> > > > > > > > > > > > > > -Enable EXT4 and FAT fs support
> > > > > > > > > > > > > All of the dts changes not in a -u-boot.dtsi file either come from
> > > > > > > > > > > > > mainline Linux or at least linux-next and have had some level upstream
> > > > > > > > > > > > > review, right?  Thanks!
> > > > > > > > > > > > Yes. All the DTS changes are merged in the Linux and are available at
> > > > > > > > > > > > arch/arm64/boot/dts/broadcom/stingray/
> > > > > > > > > > > Great.  Please reference the release you're taking these from as that
> > > > > > > > > > > will make future resyncs easier.  Thanks!
> > > > > > > > > > It's Linux v5.6.
> > > > > > > > > What's the relationship between e.g., bcm958742t.dts and ns3.dts?  I
> > > > > > > > > looked at the mainline Linux device trees and I couldn't easily see the
> > > > > > > > > correspondence.  Will the renaming complicate synchronization?
> > > > > > > > Do we need to maintain the same dt file between linux and uboot ?
> > > > > > > > Also in uboot we don't enable all devices,  how do we handle this ?
> > > > > > > If there is no U-Boot driver for a particular node then it will be
> > > > > > > ignored. It is easier to keep them in sync if they are the same in
> > > > > > > U-Boot and Linux.
> > > > > > > 
> > > > > > > > Please let me know.
> > > > > > > That is implied by your question above :-)
> > > > > > NS3 board is derivative of the existing bcm95874t board
> > > > > > (arch/arm64/boot/dts/broadcom/stingray/bcm958742t.dt)
> > > > > > Hence we have different dt for NS3 in Linux but it is not yet upstremed.
> > > > > > 
> > > > > > I compared the dt file size between uboot and Linux.
> > > > > > Uboot dt size = 9K
> > > > > > Linux dt size  = 41K (32K extra)
> > > > > > 
> > > > > > In uboot we have 8MB non-volatile SPI flash memory.
> > > > > > Out of 8MB, 1.5MB is allocated to fip.bin image and remaining 6.5MB
> > > > > > space is allocated to other components
> > > > > > like nitor/bnxt firmware image, DDR shmoo value and for backup image.
> > > > > > 
> > > > > > uboot.bin is part of the fip.bin image. If we pull Linux dt files this
> > > > > > will use extra 33K memory of allocated 1.5MB.
> > > > > > This increase in 33K will reduce total memory availability for u-boot
> > > > > > and other features (like ARM trusted firmware, Op-TEE OS) development
> > > > > > in future.
> > > > > > Hence we anticipate qpsi memory shortage going ahead for new features.
> > > > > > 
> > > > > > So please let me know your view on maintaining different dt files in uboot.
> > > > > Sounds like you have plenty of memory, actually. Is U-Boot the first
> > > > > thing to load?
> > > > > 
> > > > > I think it is important to use the same filename and have the same DT
> > > > > contents where they are present in U-Boot. But if you want to leave
> > > > > out nodes, etc., that seems OK to me. It should be easy enough to meld
> > > > > in the updates later.
> > > > > 
> > > > > I wonder if we should add a way to drop unused nodes for U-Boot
> > > > > proper, like we do for SPL?
> > > > We have that for a little while now, OF_DTB_PROPS_REMOVE, from trying to
> > > > trim things down for tbs2910.
> > > > 
> > > For tbs2910 we remove some properties, not whole nodes, from the dtb. Is
> > > it possible to also remove complete nodes? This would help even more for
> > > size reduction, I think.
> > Ah, that I think not.  Another idea to keep in mind for the dtoc
> > enhancements perhaps?  There is very much a use case of having a dtb (or
> > set of dtbs) and a U-Boot (full or SPL) and not needing/wanting to pass
> > our DTB on to the OS so both discarding things from the DTB and from
> > U-Boot based on this knowledge would be great.
> > 
> This enhancement sounds more to extend the current u-boot.dtsi feature, to
> include just specific nodes in the dtb, which currently works for SPL. A
> first step towards this direction could be to add a configuration option to
> use the same DTB for  both SPL and U-Boot, which would be a reduced version
> if the proper u-boot.dtsi is found.
> 
> What do you think?

I think there's another RFC patch that dropped a ton of not-needed nodes
via the -u-boot.dtsi file but that's also less than ideal since it's
manual.

> Regarding dtoc, currently is used to parse dtb and to convert this info to C
> structures, which doesn't seems to be the desired goal here.

So, what made me think of dtoc is that we aren't so much tied to device
trees because we want device trees, but rather we're tied to device
trees because that's the common format for describing hardware in a
machine readable format.

While this is more appropriate to the RFC thread about tiny-DM or some
other idea, what keeps popping to my mind is that we have few cases
where the device tree we work from is being passed to us from some
outside source.  Most of the time we're being told at build time the
device tree, or sometimes trees, that will ever be used on a platform at
run time.  How can we use that information to discard never-will-be-used
information?  If we've turned the device trees to C, then we can <do
something I haven't figured out the details on> and have the linker
discard things.

-- 
Tom
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