Date: Wed, 8 Aug 2012 20:59:15 +0530
From: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
To: Felix Fietkau <nbd@openwrt.org>
CC: <linux-wireless@vger.kernel.org>, <linville@tuxdriver.com>,
	<rodrigue@qca.qualcomm.com>
Subject: Re: [PATCH 3.6 4/4] ath9k_hw: enable PA linearization
Message-ID: <20120808152911.GD2041@vmraj-lnx.qualcomm.com> (sfid-20120808_172751_175324_DA0E8060)
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On Wed, Aug 08, 2012 at 05:12:25PM +0200, Felix Fietkau wrote:
> On 2012-08-08 4:55 PM, Rajkumar Manoharan wrote:
> > On Tue, Aug 07, 2012 at 03:06:12PM +0200, Felix Fietkau wrote:
> >> This feature had been disabled in ath9k because the code to support
> >> it was incomplete, but now the code is in sync with the internal QCA
> >> codebase, so it's time to enable it.
> >> 
> >> On many newer devices, the calibration is assumed to be done with PA
> >> linearization enabled.
> >> 
> >> Tests with a particular AR933x device showed that the signal emitted
> >> at full power was highly distorted and unreliable with PA linearization
> >> disabled. With this patch, the signal becomes clear and stability
> >> is improved.
> >> 
> > We faced stability issues with 938x chipsets when paprd is enabled. The commit
> > 6f4810101a629b31b5427872a09ea092cfc5c4bd states one of the issue. Even if it
> > helps for AR933x, let us enable it only for that chip alone.
> That was in January 2011, lots of bugs have been fixed since then,
> initvals have been updated, EEPROM code has changed, ...
> 
> The internal QCA codebase enables PAPRD for all AR93xx devices that
> support it, meaning non-PAPRD tx receives much less test coverage there.
> 
> While this issue has only been visible on a particular AR933x device, I
> believe this is not the only one that's going to be affected, as the
> EEPROM of any new device is calibrated for PAPRD-enabled operation.
> 
> If you don't want to enable it now, when do you think would be the right
> time to enable it? Before I sent this patch, I did a detailed code
> review to make sure that any obvious code discrepancies in PAPRD between
> the internal codebase and ath9k are dealt with.
> 
> What else is needed to get this issue sorted out?
>
Yes. it was disabled a long time back. Im completely fine with enabling the
feature. I want to make sure that we should not endup again with the same issues.
Atleast we should validite the one mentioned in the commit
6f4810101a629b31b5427872a09ea092cfc5c4bd

-Rajkumar