Re: [PATCH] watchdog: dw_wdt: dont build for avr32

From: Sudip Mukherjee
Date: Sun May 01 2016 - 05:04:57 EST

On Sunday 01 May 2016 02:13 AM, Guenter Roeck wrote:
On Sat, Apr 30, 2016 at 05:36:51PM -0700, Guenter Roeck wrote:
On Sat, Apr 30, 2016 at 07:38:28PM +0100, Sudip Mukherjee wrote:
On Tue, Apr 12, 2016 at 11:01:28AM -0700, Guenter Roeck wrote:
On Tue, Apr 12, 2016 at 05:58:20PM +0300, Andy Shevchenko wrote:
On Tue, Apr 12, 2016 at 4:39 PM, Sudip Mukherjee
<sudipm.mukherjee@xxxxxxxxx> wrote:
On Tuesday 12 April 2016 06:36 PM, Guenter Roeck wrote:

On 04/11/2016 10:51 PM, Sudip Mukherjee wrote:

The build of avr32 allmodconfig fails with the error:
ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!

This means there is a direct 64 bit divide operation in the driver,
which we should identify and fix.

This driver will quite likely never be used on AVR32. Do we need to
fix this due to some other architectures?

yes, there is.

in function: kempld_wdt_set_stage_timeout()
remainder = do_div(stage_timeout64, prescaler);

Any idea how to fix it?

Not easy, however, prescaler value is ((1 << 21) - 1) which someone
might consider as (1 << 21) with lost in precision.

Thus, shift on 20 bits right, add last bit to the value and shift on 1
bit right more.

Sorry, I am missing something. do_div() should work fine with any 32 bit value
as divisor, no matter what that value is. Why does it fail here ? And why does
it work if I pass 0x1fffff as second parameter to do_div() directly ?

Please let me know what i can do here to help solve the problem.
linux-next continues to fail for avr32, and to make matters worse we
also have the similar problem in btrfs.

ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!
ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!

Adding Chris to CC if he has some idea how to solve this error for btrfs.
Build log for next-20160429 is at:

Try the patch below.


Sorry, patch wasn't complete.


From c684f2cf54ecb256007288af23c24bfcdb2bbace Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@xxxxxxxxxxxx>
Date: Sat, 30 Apr 2016 17:29:14 -0700
Subject: [PATCH] avr32: __div64_const32 is not ok

Building avr32 images may fail with errors such as

ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!
ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!

gcc for avr32 generates those symbols for certain constants used
as divisor in do_div(). The problem can be avoided by setting
__div64_const32_is_OK to false for the architecture.

Cc: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
arch/avr32/include/asm/Kbuild | 1 -
arch/avr32/include/asm/div64.h | 3 +++
2 files changed, 3 insertions(+), 1 deletion(-)
create mode 100644 arch/avr32/include/asm/div64.h

diff --git a/arch/avr32/include/asm/Kbuild b/arch/avr32/include/asm/Kbuild
index 241b9b9729d8..d2be4688ac7b 100644
--- a/arch/avr32/include/asm/Kbuild
+++ b/arch/avr32/include/asm/Kbuild
@@ -3,7 +3,6 @@ generic-y += clkdev.h
generic-y += cputime.h
generic-y += delay.h
generic-y += device.h
-generic-y += div64.h
generic-y += emergency-restart.h
generic-y += exec.h
generic-y += futex.h
diff --git a/arch/avr32/include/asm/div64.h b/arch/avr32/include/asm/div64.h
new file mode 100644
index 000000000000..1f3328e178df
--- /dev/null
+++ b/arch/avr32/include/asm/div64.h
@@ -0,0 +1,3 @@
+#define __div64_const32_is_OK false
+#include <asm-generic/div64.h>

It looks like this patch has fixed about the error about the watchdog but for some reason I am still getting the error about the btrfs.

ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!