hi:
> Probably because in 2.6.30 you only cast the result of 32-bit multiplies
> to 64 bits. In the 2.6.33 kernel, the mutliplies are 64-bit as the
> 0x000010c7ull constant is 64-bit...
>> void __udelay(unsigned long us)
>> {
>> unsigned int lpj = current_cpu_data.udelay_val;
>>
>> __delay(((unsigned long long)(us * 0x000010c7 * HZ * lpj)) >> 32);
so that means (us * 0x000010c7 * HZ * lpj) is calculated at 32-bits and finally
(unsigned long long) cast it as 64-bits?
if i remember correctly, "64bit cast to 32-bits" is possible get 0
value, since high bits cast out.
But how 34-bits cast to 64-bits will make the value as 0 if original
low 32-bits value is non-zero?
appreciate your reply,
miloody
>> 80306ed0: 00001821 move v1,zero
>> 80306ed4: 00601021 move v0,v1
>> #include<asm/compiler.h>
>> #include<asm/war.h>
>>
>> inline void __delay(unsigned int loops)
>> {
>> __asm__ __volatile__ (
>> 80306ed8: 1440ffff bnez v0,80306ed8 <__udelay+0x8>
>> 80306edc: 2442ffff addiu v0,v0,-1
>> void __udelay(unsigned long us)
>
>> I have double checked the __delay source code of 2.6.33.4
>> and the dis-assemblies:
>
>> void __udelay(unsigned long us)
>> {
>> unsigned int lpj = current_cpu_data.udelay_val;
>>
>> __delay((us * 0x000010c7ull * HZ * lpj) >> 32);
>> 802f7310: 3c02804f lui v0,0x804f
>> 802f7314: 8c429360 lw v0,-27808(v0)
>> 802f7318: 3c050010 lui a1,0x10
>> 802f731c: 34a56256 ori a1,a1,0x6256
>> 802f7320: 00450019 multu v0,a1
>> 802f7324: 00002821 move a1,zero
>> 802f7328: 00001012 mflo v0
>> 802f732c: 00001810 mfhi v1
>> 802f7330: 00a20018 mult a1,v0
>> 802f7334: 70640000 madd v1,a0
>> 802f7338: 00003012 mflo a2
>> 802f733c: 00440019 multu v0,a0
>> 802f7340: 00001810 mfhi v1
>> 802f7344: 00c31021 addu v0,a2,v1
>> #include<asm/compiler.h>
>> #include<asm/war.h>
>>
>> inline void __delay(unsigned int loops)
>> {
>> __asm__ __volatile__ (
>> 802f7348: 1440ffff bnez v0,802f7348 <__udelay+0x38>
>> 802f734c: 2442ffff addiu v0,v0,-1
>> void __udelay(unsigned long us)
>> {
>> unsigned int lpj = current_cpu_data.udelay_val;
>>
>> __delay((us * 0x000010c7ull * HZ * lpj)>> 32);
>> }
>> 802f7350: 03e00008 jr ra
>
> WBR, Sergei
>
--
Regards,
