linux-kernel - Re: [PATCH 0/7] microblaze: fix various problems in building boot images

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Message-ID: <18fb7c8b-2b47-eb39-d80b-7137e7db466b@xilinx.com>
Date:   Fri, 7 Dec 2018 16:19:41 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Simek <monstr@...str.eu>
CC:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH 0/7] microblaze: fix various problems in building boot
 images

On 07. 12. 18 14:29, Michal Simek wrote:
> On 07. 12. 18 12:29, Masahiro Yamada wrote:
>> On Thu, Dec 6, 2018 at 11:55 PM Michal Simek <monstr@...str.eu> wrote:
>>>
>>> On 03. 12. 18 8:50, Masahiro Yamada wrote:
>>>> This patch set fixes various issues in microblaze Makefiles.
>>>>
>>>> BTW, "simpleImage.<dt>" works like a phony target to generate the
>>>> following four images, where the first three are just aliases.
>>>>
>>>>  - arch/microblaze/boot/simpleImage.<dt>:
>>>>          identical to arch/microblaze/boot/linux.bin
>>>>
>>>>  - arch/microblaze/boot/simpleImage.<dt>.unstrip:
>>>>          identical to vmlinux
>>>>
>>>>  - arch/microblaze/boot/simpleImage.<dt>.ub:
>>>>          identical to arch/microblaze/boot/linux.bin.ub
>>>>
>>>>  - arch/microblaze/boot/simpleImage.<dt>.strip:
>>>>          stripped vmlinux
>>>>
>>>> I am not sure how much useful those copies are,
>>>> but, I tried my best to keep the same behavior.
>>>>
>>>> IMHO, I guess DTB=<dt> would be more sensible,
>>>> but it is up to Michal.
>>>>
>>>>
>>>>
>>>> Masahiro Yamada (7):
>>>>   microblaze: fix cleaning of boot images
>>>>   microblaze: adjust the help to the real behavior
>>>>   microblaze: move "... is ready" message to arch/microblaze/Makefile
>>>>   microblaze: fix multiple bugs in arch/microblaze/boot/Makefile
>>>>   microblaze: add linux.bin* and simpleImage.* to PHONY
>>>>   microblaze: fix race condition in building boot images
>>>>   microblaze: remove the unneeded code just in case file copy fails
>>>>
>>>>  arch/microblaze/Makefile          | 14 +++++++++-----
>>>>  arch/microblaze/boot/Makefile     | 33 +++++++++++++++++----------------
>>>>  arch/microblaze/boot/dts/Makefile |  5 +----
>>>>  3 files changed, 27 insertions(+), 25 deletions(-)
>>>>
>>>
>>> One more thing I have in my mind for a while is that will be good to
>>> configure kernel build flags from DT and completely get rid of these
>>> symbols.
>>>
>>> XILINX_MICROBLAZE0_USE_MSR_INSTR
>>> XILINX_MICROBLAZE0_USE_PCMP_INSTR
>>> XILINX_MICROBLAZE0_USE_BARREL
>>> XILINX_MICROBLAZE0_USE_DIV
>>> XILINX_MICROBLAZE0_USE_HW_MUL
>>> XILINX_MICROBLAZE0_USE_FPU
>>>
>>> It means setup CPUFLAGS based on extracting that values from DT that it
>>> all the time match the hardware.
>>> It will also simplify all the CPUFLAGS logic which is in
>>> arch/microblaze/Makefile.
>>>
>>> Do you have any idea how this can be done?
>>
>>
>> I have no idea.
>>
>> Parsing DTS with sed or something would be possible, but ugly.
>>
>> In my opinion, the kernel should be multi platform image,
>> in other words, it is the least common denominator
>> of supported platforms.
>>
>> So, the kernel should enable all features that may or may not be used
>> depending on platform.
>>
>> I do not know if this works for MB.
> 
> Microblaze is soft core CPU where you can select if you want to have it
> with multiplier, divider, barrel shifter, etc.
> You can of course say that you don't have them and you have "universal"
> kernel but very slow.
> That's why user has to setup these configs which are converted to cflags
> to say GCC what can be used.
> And these configs can be simply parsed from dt.
> 
> For example like this based on dtb (quick hack)
> 
> for i in `echo use-msr-instr use-pcmp-instr use-barrel use-div
> use-hw-mul use-fpu`; do
> 	UPPER=`echo $i | tr '-' '_' | tr '[a-z]' '[A-Z}'`
> 	echo $i $UPPER;
> 
> 	VAR=`fdtget -t i $FILE/arch/microblaze/boot/dts/system.dtb /cpus/cpu@0/
> xlnx,$i`
> 	FLAGS+="CONFIG_XILINX_MICROBLAZE0_${UPPER}=${VAR} "
> done
> 
> make $FLAGS
> 
> 
> When simpleImage is requested dt could be parsed to setup proper build
> flags.

One more thing I found is that I have done these changes

diff --git a/arch/microblaze/kernel/setup.c b/arch/microblaze/kernel/setup.c
index bbd6968ce55b..dc6a6fee3ae2 100644
--- a/arch/microblaze/kernel/setup.c
+++ b/arch/microblaze/kernel/setup.c
@@ -153,11 +153,13 @@ void __init machine_early_init(const char
*cmdline, unsigned int ram,
 #endif

 #if CONFIG_XILINX_MICROBLAZE0_USE_MSR_INSTR
+#error MSR is enabled
        if (msr) {
                pr_info("!!!Your kernel has setup MSR instruction but ");
                pr_cont("CPU don't have it %x\n", msr);
        }
 #else
+#error MSR is not enabled
        if (!msr) {
                pr_info("!!!Your kernel not setup MSR instruction but ");
                pr_cont("CPU have it %x\n", msr);

and run MSR with 1
make defconfig && make CONFIG_XILINX_MICROBLAZE0_USE_MSR_INSTR=1
arch/microblaze/kernel/setup.o
it errors #error MSR is enabled
and all is good.

And when I run MSR with 0
make defconfig && make CONFIG_XILINX_MICROBLAZE0_USE_MSR_INSTR=0
arch/microblaze/kernel/setup.o
also getting #error MSR is enabled
which is wrong.

Is there any rule what can be setup at compilation time?

Thanks,
Michal