Re: libata and DMA quirks

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Benjamin Herrenschmidt wrote:
>>> The main one is that one their latest cell, they do the following
>>> "workarounds" which I never implemented in drivers/ide/ppc/pmac.c but
>>> I'd like to implement in the libata driver, unless you believe that is
>>> unnecessary:
>>>
>>> a) For any ATAPI DMA, If the transfer size is not a multiple of 16
>>> bytes, switch to PIO for this command.
>>>   
>>>       
>>    No need to do this in old driver anyway since the *IDE* core only 
>> uses DMA for block commands like READ and WRITE.
>> Not sure about libata.
>>     
>
> It doesn't use DMA to transfer the bulk of ATAPI ? I know it uses PIO
> for the CDB but the rest of the transfer isn't done with DMA ?
>   
   Like I said, DMA is used only for the *block* transfer commands for 
which the transfer size would always be a multiple of 16 bytes.

MBR, Sergei