Re: [RFC][PATCH 2/2] DSPBRIDGE: Distinguish between read or write buffers

[Omar Ramirez Luna <omar.ramirez@ti.com>]

On 2/19/2010 7:44 AM, Chitriki Rudramuni, Deepak wrote:
> Ramirez Luna, Omar wrote:
>> This patch introduces the check to differentiate the buffers
>> coming to the dsp through bridgedriver. So far they can be
>> input (read) or output (write) or rw (which are treated the
>> same way as an output buffer), this distinctions are made from
>> dsp perspective.
>>
>> Since this needs to be checked on map function, unused
>> bits (16, 15) of flags were used to check for this argument.
>>
>> As 128 byte alignment limitation doesn't affect input buffers
>> only writable buffers are checked. Default value for read buffers
>> is set to be 1, this will enforce that users of bridge will fill
>> the flags with significant values otherwise (if enabled) check
>> will reject buffers not aligned to 128 bytes (even if they fall in
>> the input category).
>>
>> Signed-off-by: Omar Ramirez Luna<omar.ramirez@ti.com>
>> ---
>>   drivers/dsp/bridge/rmgr/proc.c |   16 ++++++++++++----
>>   1 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/dsp/bridge/rmgr/proc.c b/drivers/dsp/bridge/rmgr/proc.c
>> index 78a31ef..4fe20ed 100644
>> --- a/drivers/dsp/bridge/rmgr/proc.c
>> +++ b/drivers/dsp/bridge/rmgr/proc.c
>> @@ -71,6 +71,12 @@
>>
>>   #define DSP_CACHE_LINE 128
>>
>> +#define BUFMODE_MASK	(3<<  14)
>> +
>> +/* Buffer modes from DSP perspective */
>> +#define RBUF		0x1	/* Input buffer */
>> +#define WBUF		0x2	/* Output Buffer */
>> +
>>   extern char *iva_img;
>>
>>   /*  ----------------------------------- Globals */
>> @@ -1297,11 +1303,13 @@ DSP_STATUS PROC_Map(DSP_HPROCESSOR hProcessor, void *pMpuAddr, u32 ulSize,
>>   		 pReqAddr, ulMapAttr, ppMapAddr);
>>
>>   #ifdef CONFIG_BRIDGE_CACHE_LINE_CHECK
>> -	if (!IS_ALIGNED((u32)pMpuAddr, DSP_CACHE_LINE) ||
>> -	    !IS_ALIGNED(size, DSP_CACHE_LINE)) {
>> -		pr_err("%s: not aligned: 0x%x (%d)\n", __func__,
>> +	if ((ulMapAttr&  BUFMODE_MASK) != RBUF) {
> What if the result of (ulMapAttr&  BUFMODE_MASK) is invalid,still it enters the loop.Since the condition is for writable buffers only,Isn't it better to use "if ((ulMapAttr&  BUFMODE_MASK) == WBUF)" condition?
>

Description:
"this will enforce that users of bridge will fill
the flags with significant values otherwise (if enabled) check
will reject buffers not aligned to 128 bytes (even if they fall in
the input category)"

Let say you enable the check but bits are not used (meaning they are set 
to 0), bridge doesn't have a way to distinguish if this is expected or 
if you just forgot to fill them.

Anyway, if such a strict check is not required then I guess we can use 
only 1 bit (0 = READ, 1 = WRITE).

In short: if you are enabling the check then set the proper value for 
the bit.

>> +		if (!IS_ALIGNED((u32)pMpuAddr, DSP_CACHE_LINE) ||
>> +		    !IS_ALIGNED(ulSize, DSP_CACHE_LINE)) {
>> +			pr_err("%s: not aligned: 0x%x (%d)\n", __func__,
>>   						(u32)pMpuAddr, ulSize);
>> -		return -EFAULT;
>> +			return -EFAULT;
>> +		}
>>   	}
>>   #endif
> Regards,
> Deepak
>

- omar