Re: [PATCH v2 11/13] ath9k_hw: Disable Walsh spatial spreading for 2 chains

[Felix Fietkau <nbd@xxxxxxxxxxx>]

On 2011-08-04 7:45 PM, Rajkumar Manoharan wrote:
> On Tue, Aug 02, 2011 at 07:33:00PM +0200, Felix Fietkau wrote:
> >  On 2011-08-02 11:46 AM, Rajkumar Manoharan wrote:
> >  >On Fri, Jul 29, 2011 at 02:41:41PM +0200, Felix Fietkau wrote:
> >  >>  On 2011-07-29 2:08 PM, Rajkumar Manoharan wrote:
> >  >>  >Signed-off-by: Rajkumar Manoharan<rmanohar@xxxxxxxxxxxxxxxx>
> >  >>  >---
> >  >>  >    .../net/wireless/ath/ath9k/ar9003_2p2_initvals.h   |    2 +-
> >  >>  >    1 files changed, 1 insertions(+), 1 deletions(-)
> >  >>  >
> >  >>  >diff --git a/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h b/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h
> >  >>  >index 2339728..28b44b0 100644
> >  >>  >--- a/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h
> >  >>  >+++ b/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h
> >  >>  >@@ -636,7 +636,7 @@ static const u32 ar9300_2p2_baseband_postamble[][5] = {
> >  >>  >    	{0x00009e44, 0x02321e27, 0x02321e27, 0x02291e27, 0x02291e27},
> >  >>  >    	{0x00009e48, 0x5030201a, 0x5030201a, 0x50302012, 0x50302012},
> >  >>  >    	{0x00009fc8, 0x0003f000, 0x0003f000, 0x0001a000, 0x0001a000},
> >  >>  >-	{0x0000a204, 0x000037c0, 0x000037c4, 0x000037c4, 0x000037c0},
> >  >>  >+	{0x0000a204, 0x000036c0, 0x000036c4, 0x000036c4, 0x000036c0},
> >  >>  >    	{0x0000a208, 0x00000104, 0x00000104, 0x00000004, 0x00000004},
> >  >>  >    	{0x0000a22c, 0x01026a2f, 0x01026a2f, 0x01026a2f, 0x01026a2f},
> >  >>  >    	{0x0000a230, 0x0000000a, 0x00000014, 0x00000016, 0x0000000b},
> >  >>  That patch makes no sense, it disables Walsh spatial spreading in
> >  >>  the initvals, but the driver still enables it in
> >  >>  ar9003_hw_set_channel_regs.
> >  >>  By the way, why should we disable Walsh spatial spreading?
> >  >>
> >  >The initval table is filled with default values recommended in register spec.
> >  >This patch does that. And these default value can be altered during chip bringup
> >  >based on chip family.
> >  OK, then the patch description should probably mention that this
> >  change has no effect and does not actually disable this feature in
> >  general, since the driver unconditionally enables it elsewhere.
> Felix,
>
> The Walsh bit is disabled for regulatory consideration.
>
> In the FCC rulings, only transmissions that are completely non-coherent, are
> allowed to waive the array gain contribution to EIRP for multi-transmit configurations.
> The use of 2-stream with 2 transmit and use of 3-steam with 3 transmit qualifies
> for this spatial multiplexing MIMO classification as long as the streams are
> directly mapped to each radio (not Walsh spread prior to splitting to multiple radios)
>
> And also Walsh has to be disabled in ar9003_hw_set_channel_regs.
> Thanks for finding out. Will send followup patch.
Wouldn't that only be relevant if the regdomain/country setting is a FCC 
one *and* the configured tx power is close to the limit?
It seems to me that if either of those is not the case, it should be 
valid to keep walsh spatial spreading enabled.

- Felix
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