Re: [Xen-devel] [PATCH v4 08/10] arm: add QEMU, Rcar3 and MPSoC configs

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 1 Jun 2018, Julien Grall wrote:
> Hi Stefano,
> Sorry for formatting.
> 
> On Thu, 31 May 2018, 22:50 Stefano Stabellini, <sstabellini@xxxxxxxxxx> wrote:
>       Add a "Platform Support" menu with three umbrella kconfig options: QEMU,
>       RCAR3 and MPSOC. They enable the required options for their hardware
>       platform.
> 
> 
> This patch is nothing close to what we discussed. As far as I can tell, the 
> tiny.config will end up to select all the platforms
> with their driver. It will not be possible to deselect the driver selected 
> for a platform afterwards.
> 
> I still think the best if providing a choice list where only one option can 
> be selected. I would like to understand why you
> didn't go this path.

Yes, sorry, I didn't explain why I did this and what I told you on the
call was wrong, adding to the confusion.

First, it is true that `make olddefconfig' is run automatically on any
make target.

Except for `make menuconfig', that's special. If you copy a partial
config (like tiny.config) to .config, then execute `make menuconfig',
the menu gets automatically populated with the missing values using
defaults (as if olddefconfig was run), but it won't automatically save
them to file (fortunately!!).  That means that all the platform options
below (QEMU, RCAR3, MPSOC) will show as selected in the menu, but if the
user deselects two of them, for instance QEMU and RCAR3, the result is
that *only* MPSOC and related options will be written down to the
.config.

The kconfig infrastructure is not as bad as I initially thought :-)
In short, the following steps work:

- copy tiny.config to .config
- make menuconfig -> deselect QEMU and RCAR3, save .config
- as a results the final .config will have:

  CONFIG_MPSOC=y
  CONFIG_HAS_CADENCE_UART=y

but it won't have GICV3, any other platform options, or any other uart
drivers. Moreover, even NR_CPUS will be set correctly:
  
  CONFIG_NR_CPUS=4

I am attaching the .config for MPSOC produced using these steps as a
reference. More on the NR_CPUS topic in my next email reply.


>       In the case of the MPSOC that has a platform file under
>       arch/arm/platforms/, build the file if MPSOC.
> 
>       Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>       CC: artem_mygaiev@xxxxxxxx
>       CC: volodymyr_babchuk@xxxxxxxx
> 
>       ---
>       Changes in v4:
>       - fix GICv3/GICV3
>       - default y to all options
>       - build xilinx-zynqmp if MPSOC
>       ---
>        xen/arch/arm/Kconfig            |  2 ++
>        xen/arch/arm/platforms/Kconfig  | 30 ++++++++++++++++++++++++++++++
>        xen/arch/arm/platforms/Makefile |  2 +-
>        3 files changed, 33 insertions(+), 1 deletion(-)
>        create mode 100644 xen/arch/arm/platforms/Kconfig
> 
>       diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
>       index 2b87111..75cacfb 100644
>       --- a/xen/arch/arm/Kconfig
>       +++ b/xen/arch/arm/Kconfig
>       @@ -213,6 +213,8 @@ config ARM64_HARDEN_BRANCH_PREDICTOR
>        config ARM32_HARDEN_BRANCH_PREDICTOR
>            def_bool y if ARM_32 && HARDEN_BRANCH_PREDICTOR
> 
>       +source "arch/arm/platforms/Kconfig"
>       +
>        source "common/Kconfig"
> 
>        source "drivers/Kconfig"
>       diff --git a/xen/arch/arm/platforms/Kconfig 
> b/xen/arch/arm/platforms/Kconfig
>       new file mode 100644
>       index 0000000..fea8f9a
>       --- /dev/null
>       +++ b/xen/arch/arm/platforms/Kconfig
>       @@ -0,0 +1,30 @@
>       +menu "Platform Support"
>       +
>       +config QEMU
>       +       bool "QEMU aarch virt machine support"
>       +       default y
>       +       depends on ARM_64
>       +       select GICV3
>       +       select HAS_PL011
>       +       ---help---
>       +       Enable all the required drivers for QEMU aarch64 virt emulated
>       +       machine.
>       +
>       +config RCAR3
>       +       bool "Renesas RCar3 support"
>       +       default y
>       +       depends on ARM_64
>       +       select HAS_SCIF
>       +       ---help---
>       +       Enable all the required drivers for Renesas RCar3
>       +
>       +config MPSOC
>       +       bool "Xilinx Ultrascale+ MPSoC support"
>       +       default y
>       +       depends on ARM_64
>       +       select HAS_CADENCE_UART
>       +       select ARM_SMMU
>       +       ---help---
>       +       Enable all the required drivers for Xilinx Ultrascale+ MPSoC
>       +
>       +endmenu
>       diff --git a/xen/arch/arm/platforms/Makefile 
> b/xen/arch/arm/platforms/Makefile
>       index 80e555c..f4ff411 100644
>       --- a/xen/arch/arm/platforms/Makefile
>       +++ b/xen/arch/arm/platforms/Makefile
>       @@ -8,4 +8,4 @@ obj-$(CONFIG_ARM_64) += seattle.o
>        obj-y += sunxi.o
>        obj-$(CONFIG_ARM_64) += thunderx.o
>        obj-$(CONFIG_ARM_64) += xgene-storm.o
>       -obj-$(CONFIG_ARM_64) += xilinx-zynqmp.o
>       +obj-$(CONFIG_MPSOC)  += xilinx-zynqmp.o
>       --
>       1.9.1
> 
> 
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> 
> 
>

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