[PATCH 1/1] sh: add support for cmpxchg on u8 and u16 pointers

[Liam Beguin]

The kernel test bot reported[1] that using set_mask_bits on a u8 causes
the following issue on SuperH:

    >> ERROR: modpost: "__cmpxchg_called_with_bad_pointer" 
[drivers/phy/ti/phy-tusb1210.ko] undefined!

Add support for cmpxchg on u8 and u16 pointers.

[1] https://lore.kernel.org/patchwork/patch/1288894/#1485536

Reported-by: kernel test robot <l...@intel.com>
Signed-off-by: Liam Beguin <liambeg...@gmail.com>
---

Hi,

This was reported by the kernel test bot on an architecture I can't
really test on. I was only able to make sure the build succeeds, but
nothing more.
This patch is based on the __cmpxchg_u32 impletmentation and seems
incomplete based on the different cmpxchg headers I can find.

Do these function need to be impletmented in each header
simulataneously?

Thanks,
Liam

 arch/sh/include/asm/cmpxchg-irq.h | 27 +++++++++++++++++++++++++++
 arch/sh/include/asm/cmpxchg.h     |  5 +++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/arch/sh/include/asm/cmpxchg-irq.h 
b/arch/sh/include/asm/cmpxchg-irq.h
index 07d3e7f08389..918c4153a930 100644
--- a/arch/sh/include/asm/cmpxchg-irq.h
+++ b/arch/sh/include/asm/cmpxchg-irq.h
@@ -51,4 +51,31 @@ static inline unsigned long __cmpxchg_u32(volatile int *m, 
unsigned long old,
        return retval;
 }
 
+static inline unsigned long __cmpxchg_u16(volatile u16 *m, unsigned long old,
+       unsigned long new)
+{
+       u16 retval;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       retval = *m;
+       if (retval == old)
+               *m = new;
+       local_irq_restore(flags);
+       return (unsigned long)retval;
+}
+
+static inline unsigned long __cmpxchg_u8(volatile u8 *m, unsigned long old,
+       unsigned long new)
+{
+       u8 retval;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       retval = *m;
+       if (retval == old)
+               *m = new;
+       local_irq_restore(flags);
+       return (unsigned long)retval;
+}
 #endif /* __ASM_SH_CMPXCHG_IRQ_H */
diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
index e9501d85c278..7d65d0fd1665 100644
--- a/arch/sh/include/asm/cmpxchg.h
+++ b/arch/sh/include/asm/cmpxchg.h
@@ -56,8 +56,9 @@ static inline unsigned long __cmpxchg(volatile void * ptr, 
unsigned long old,
                unsigned long new, int size)
 {
        switch (size) {
-       case 4:
-               return __cmpxchg_u32(ptr, old, new);
+       case 4: return __cmpxchg_u32((int *)ptr, old, new);
+       case 2: return __cmpxchg_u16((u16 *)ptr, old, new);
+       case 1: return __cmpxchg_u8((u8 *)ptr, old, new);
        }
        __cmpxchg_called_with_bad_pointer();
        return old;
-- 
2.27.0