linux-kernel - Re: [PATCH v3 1/8] SOC: brcmstb: add memory API

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Message-ID: <20171215171440.GB32131@red-moon>
Date:   Fri, 15 Dec 2017 17:14:40 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Jim Quinlan <jim2101024@...il.com>, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jonas Gorski <jonas.gorski@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Linux-MIPS <linux-mips@...ux-mips.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Kevin Cernekee <cernekee@...il.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/8] SOC: brcmstb: add memory API

On Tue, Dec 12, 2017 at 03:14:04PM -0600, Bjorn Helgaas wrote:
> [+cc Lorenzo]
> 
> On Tue, Dec 12, 2017 at 03:53:28PM -0500, Jim Quinlan wrote:
> > On Tue, Dec 5, 2017 at 3:59 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> > > On Tue, Nov 14, 2017 at 05:12:05PM -0500, Jim Quinlan wrote:
> > >> From: Florian Fainelli <f.fainelli@...il.com>
> > >>
> > >> This commit adds a memory API suitable for ascertaining the sizes of
> > >> each of the N memory controllers in a Broadcom STB chip.  Its first
> > >> user will be the Broadcom STB PCIe root complex driver, which needs
> > >> to know these sizes to properly set up DMA mappings for inbound
> > >> regions.
> > >>
> > >> We cannot use memblock here or anything like what Linux provides
> > >> because it collapses adjacent regions within a larger block, and here
> > >> we actually need per-memory controller addresses and sizes, which is
> > >> why we resort to manual DT parsing.
> > >>
> > >> Signed-off-by: Jim Quinlan <jim2101024@...il.com>
> > >> ---
> > >>  drivers/soc/bcm/brcmstb/Makefile |   2 +-
> > >>  drivers/soc/bcm/brcmstb/memory.c | 172 +++++++++++++++++++++++++++++++++++++++
> > >>  include/soc/brcmstb/memory_api.h |  25 ++++++
> > >>  3 files changed, 198 insertions(+), 1 deletion(-)
> > >>  create mode 100644 drivers/soc/bcm/brcmstb/memory.c
> > >>  create mode 100644 include/soc/brcmstb/memory_api.h
> > >>
> > >> diff --git a/drivers/soc/bcm/brcmstb/Makefile b/drivers/soc/bcm/brcmstb/Makefile
> > >> index 9120b27..4cea7b6 100644
> > >> --- a/drivers/soc/bcm/brcmstb/Makefile
> > >> +++ b/drivers/soc/bcm/brcmstb/Makefile
> > >> @@ -1 +1 @@
> > >> -obj-y                                += common.o biuctrl.o
> > >> +obj-y                                += common.o biuctrl.o memory.o
> > >> diff --git a/drivers/soc/bcm/brcmstb/memory.c b/drivers/soc/bcm/brcmstb/memory.c
> > >> new file mode 100644
> > >> index 0000000..eb647ad9
> > >> --- /dev/null
> > >> +++ b/drivers/soc/bcm/brcmstb/memory.c
> > >
> > > I sort of assume based on [1] that every new file should have an SPDX
> > > identifier ("The Linux kernel requires the precise SPDX identifier in
> > > all source files") and that the actual text of the GPL can be omitted.
> > >
> > > Only a few files in drivers/pci currently have an SPDX identifier.  I
> > > don't know if that's oversight or work-in-progress or what.
> > >
> > > [1] https://lkml.kernel.org/r/20171204212120.484179273@linutronix.de
> > >
> > 
> > Bjorn, Did you get a chance to review the other commits of this
> > submission (V3)?  I would like any additional feedback before I send
> > out a V4 with SPDX fixes.  Thanks, JimQ
> 
> Lorenzo is taking over drivers/pci/host/* and he'll no doubt have some
> comments when he gets to this.  I'll point out a few quick formatting
> things in the meantime.

I need some time to review the code but overall I am quite worried about
patches 1 and 4 in particular, it is ok to have platform host bridge
drivers but we can't rewrite a DMA layer for a specific host bridge, I
really do not like that - it is just not manageable from a maintenance
perspective for the mainline kernel.

Lorenzo