RE: [PATCH] NTB: Register and offset values fix for memory window

["Allen Hubbe" <Allen.Hubbe@dell.com>]

From: Shyam Sundar S K
> On 11/22/2016 7:49 PM, Allen Hubbe wrote:
> > Instead, limit the number of memory windows actually used by ntb_transport, such that
> ntb_transport can configure those memory windows using only the available scratchpads.  If
> there are not enough scratchpads to exchange values for all of the memory windows, then
> ntb_transport should limit itself to use fewer memory windows.
> >
> 
> Allen, I get your point. So, you are asking to limit the number of memory windows we
> advertise in our driver since there are less number of scratchpads available when we have
> to configure the 3rd
> window. I believe you are asking me to do
> 
> -       ndev->mw_count = AMD_MW_CNT;
> +       ndev->mw_count = AMD_MW_CNT - 1;
> 
> in amd_init_ntb(). Is this understanding correct ?

That would work, but it would limit other transport drivers from using all the memory windows of your device.
 
This is the change I meant to describe, in ntb_transport:

static int ntb_transport_probe(struct ntb_client *self, struct ntb_dev *ndev)
{
...
	mw_count = ntb_mw_count(ndev);

Instead of this:

	nt->mw_count = mw_count;

Limit the mw count like this:

	spad_count = ntb_spad_count(ndev);

	max_mw_count_for_spads = some_arithmetic(spad_count);

	nt->mw_count = min(mw_count, max_mw_count_for_spads);