Re: [PATCH 1/2] libata: Add two more columns to the ata_timing table.

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

David Daney wrote:

>> Hello.

>> David Daney wrote:

>>> The forthcoming OCTEON SOC Compact Flash driver needs a few more
>>> timing values than were available in the ata_timing table.  I add new
>>> columns for write_hold and read_holdz times.  The values were obtained
>>> from the Compact Flash specification Rev 4.1.

>>> Signed-off-by: David Daney <ddaney@caviumnetworks.com>

>> NAK.

>>> diff --git a/include/linux/libata.h b/include/linux/libata.h
>>> index ed3f26e..95fa9f6 100644
>>> --- a/include/linux/libata.h
>>> +++ b/include/linux/libata.h
>>
>> [...]
>>
>>>  enum ata_xfer_mask {
>>> @@ -864,6 +868,8 @@ struct ata_timing {
>>>      unsigned short cyc8b;        /* t0 for 8-bit I/O */
>>>      unsigned short active;        /* t2 or tD */
>>>      unsigned short recover;        /* t2i or tK */
>>> +    unsigned short write_hold;    /* t4 */
>>> +    unsigned short read_holdz;    /* t6z */
>>
>>
>>    Sorry for failing to notice this before but t6z is again the timing 
>> that the host can't control. Therefore I'm seeig no sense in its 
>> addition.
> 
> 
> The host cannot control t6z, but in some cases (like ours) it needs to 
> be aware of its value.  We cannot start driving the bus for access to 
> other devices until the CF stops driving it.  We need to know how long 
> to wait until it is safe to use the bus for other things.

    Re-read the spec please, the timing you need is t9 and it's much longer 
than t6 that your driver using instead.

>> I don't know how your driver is going to use it -- but most probably 
>> incorrectly...

> Thanks for that vote of confidence.

   You're welcome. :-)

> David Daney

MBR, Sergei