lkml.org 
[lkml]   [2021]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH net-next 2/4] io: add function to flush the write combine buffer to device immediately
From
Date


On 2021/7/30 17:00, Will Deacon wrote:
> Hi,
>
> On Fri, Jul 30, 2021 at 11:14:22AM +0800, Guangbin Huang wrote:
>> From: Xiongfeng Wang <wangxiongfeng2@huawei.com>
>>
>> Device registers can be mapped as write-combine type. In this case, data
>> are not written into the device immediately. They are temporarily stored
>> in the write combine buffer and written into the device when the buffer
>> is full. But in some situation, we need to flush the write combine
>> buffer to device immediately for better performance. So we add a general
>> function called 'flush_wc_write()'. We use DGH instruction to implement
>> this function for ARM64.
>>
>> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
>> Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
>> ---
>> arch/arm64/include/asm/io.h | 2 ++
>> include/linux/io.h | 6 ++++++
>> 2 files changed, 8 insertions(+)
>
> -ENODOCUMENTATION
>
Hi Will, may I consult you which document file is good to add documentation?

>> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
>> index 7fd836bea7eb..5315d023b2dd 100644
>> --- a/arch/arm64/include/asm/io.h
>> +++ b/arch/arm64/include/asm/io.h
>> @@ -112,6 +112,8 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>> #define __iowmb() dma_wmb()
>> #define __iomb() dma_mb()
>>
>> +#define flush_wc_write() dgh()
>
> I think it would be worthwhile to look at what architectures other than
> arm64 offer here. For example, is there anything similar to this on riscv,
> x86 or power? Doing a quick survery of what's out there might help us define
> a macro that can be used across multiple architectures.
>
> Thanks,
>
> Will
>
>> /*
>> * Relaxed I/O memory access primitives. These follow the Device memory
>> * ordering rules but do not guarantee any ordering relative to Normal memory
>> diff --git a/include/linux/io.h b/include/linux/io.h
>> index 9595151d800d..469d53444218 100644
>> --- a/include/linux/io.h
>> +++ b/include/linux/io.h
>> @@ -166,4 +166,10 @@ static inline void arch_io_free_memtype_wc(resource_size_t base,
>> }
>> #endif
>>
>> +/* IO barriers */
>> +
>> +#ifndef flush_wc_write
>> +#define flush_wc_write() do { } while (0)
>> +#endif
>> +
>> #endif /* _LINUX_IO_H */
>> --
>> 2.8.1
>>
> .
>

\
 
 \ /
  Last update: 2021-10-11 15:38    [W:0.105 / U:0.476 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site