Re: [PATCH 1/1] ipr: add writeq definition if needed

[Wayne Boyer <wayneb@linux.vnet.ibm.com>]

On 06/09/2010 09:20 AM, James Bottomley wrote:
> On Wed, 2010-06-09 at 08:24 -0700, Wayne Boyer wrote:
>> Compiling the driver will fail on 32 bit powerpc and other
>> architectures where writeq is not defined.  This patch adds a
>> definition for writeq.
>>
>> Signed-off-by: Wayne Boyer <wayneb@linux.vnet.ibm.com>
>> ---
>>
>>  drivers/scsi/ipr.h |    8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> Index: b/drivers/scsi/ipr.h
>> ===================================================================
>> --- a/drivers/scsi/ipr.h	2010-06-08 10:06:48.000000000 -0700
>> +++ b/drivers/scsi/ipr.h	2010-06-08 15:14:42.000000000 -0700
>> @@ -1860,4 +1860,12 @@ static inline int ipr_sdt_is_fmt2(u32 sd
>>  	return 0;
>>  }
>>
>> +#ifndef writeq
>> +static inline void writeq(u64 val, void __iomem *addr)
>> +{
>> +        writel(((u32) (val >> 32)), addr);
>> +        writel(((u32) (val)), (addr + 4));
> 
> Are you sure this is what you want?  The point about writeq is to do an
> atomic write of a 64 bit quantity.  Doing two writel's loses the
> atomicity (and can confuse some hardware if not done in the right
> order).  If this code above works correctly, why bother with the writeq?
> 

We do want to issue 8 byte MMIO writes where we can for the new adapters
for better performance.  We want to use writeq on platforms that support
it.  I did test the driver using this define with the new hardware and it
does work as expected.

-- 
Wayne Boyer
IBM - Beaverton, Oregon
LTC S/W Development - eServerIO
(503) 578-5236, T/L 775-5236