Re: [PATCH v4 2/8] MIPS: Octeon: Enable LMTDMA/LMTST operations.

[David Daney <ddaney@caviumnetworks.com>]

On 11/30/2017 01:36 PM, James Hogan wrote:
> On Tue, Nov 28, 2017 at 04:55:34PM -0800, David Daney wrote:
>> From: Carlos Munoz <cmunoz@cavium.com>
>>
>> LMTDMA/LMTST operations move data between cores and I/O devices:
>>
>> * LMTST operations can send an address and a variable length
>>    (up to 128 bytes) of data to an I/O device.
>> * LMTDMA operations can send an address and a variable length
>>    (up to 128) of data to the I/O device and then return a
>>    variable length (up to 128 bytes) response from the IOI device.
> 
> Should that be "I/O"?

Yes, I will fix the changelog.


> 
>>
>> Signed-off-by: Carlos Munoz <cmunoz@cavium.com>
>> Signed-off-by: Steven J. Hill <Steven.Hill@cavium.com>
>> Signed-off-by: David Daney <david.daney@cavium.com>
>> ---
>>   arch/mips/cavium-octeon/setup.c       |  6 ++++++
>>   arch/mips/include/asm/octeon/octeon.h | 12 ++++++++++--
>>   2 files changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
>> index a8034d0dcade..99e6a68bc652 100644
>> --- a/arch/mips/cavium-octeon/setup.c
>> +++ b/arch/mips/cavium-octeon/setup.c
>> @@ -609,6 +609,12 @@ void octeon_user_io_init(void)
>>   #else
>>   	cvmmemctl.s.cvmsegenak = 0;
>>   #endif
>> +	if (OCTEON_IS_OCTEON3()) {
>> +		/* Enable LMTDMA */
>> +		cvmmemctl.s.lmtena = 1;
>> +		/* Scratch line to use for LMT operation */
>> +		cvmmemctl.s.lmtline = 2;
> 
> Out of curiosity, is there significance to the value 2 and associated
> virtual address 0xffffffffffff8100, or is it pretty arbitrary?

Yes, there is significance.

CPU local memory starts at 0xffffffffffff8000, each line is 0x80 bytes. 
so the 2nd line starts at 0xffffffffffff8100


> 
>> +	}
>>   	/* R/W If set, CVMSEG is available for loads/stores in
>>   	 * supervisor mode. */
>>   	cvmmemctl.s.cvmsegenas = 0;
>> diff --git a/arch/mips/include/asm/octeon/octeon.h b/arch/mips/include/asm/octeon/octeon.h
>> index c99c4b6a79f4..92a17d67c1fa 100644
>> --- a/arch/mips/include/asm/octeon/octeon.h
>> +++ b/arch/mips/include/asm/octeon/octeon.h
>> @@ -179,7 +179,15 @@ union octeon_cvmemctl {
>>   		/* RO 1 = BIST fail, 0 = BIST pass */
>>   		__BITFIELD_FIELD(uint64_t wbfbist:1,
>>   		/* Reserved */
>> -		__BITFIELD_FIELD(uint64_t reserved:17,
>> +		__BITFIELD_FIELD(uint64_t reserved_52_57:6,
>> +		/* When set, LMTDMA/LMTST operations are permitted */
>> +		__BITFIELD_FIELD(uint64_t lmtena:1,
>> +		/* Selects the CVMSEG LM cacheline used by LMTDMA
>> +		 * LMTST and wide atomic store operations.
>> +		 */
>> +		__BITFIELD_FIELD(uint64_t lmtline:6,
>> +		/* Reserved */
>> +		__BITFIELD_FIELD(uint64_t reserved_41_44:4,
>>   		/* OCTEON II - TLB replacement policy: 0 = bitmask LRU; 1 = NLU.
>>   		 * This field selects between the TLB replacement policies:
>>   		 * bitmask LRU or NLU. Bitmask LRU maintains a mask of
>> @@ -275,7 +283,7 @@ union octeon_cvmemctl {
>>   		/* R/W Size of local memory in cache blocks, 54 (6912
>>   		 * bytes) is max legal value. */
>>   		__BITFIELD_FIELD(uint64_t lmemsz:6,
>> -		;)))))))))))))))))))))))))))))))))
>> +		;))))))))))))))))))))))))))))))))))))
>>   	} s;
>>   };
> 
> Regardless, the patch looks good to me.
> 
> Reviewed-by: James Hogan <jhogan@kernel.org>
> 
> Cheers
> James
>