Re: [PATCH 08/10] carl9170: phy: enable antenna diversity for 2-chain devices

[Christian Lamparter <chunkeey@gmail.com>]

On 3/12/26 11:38 AM, Masi Osmani wrote:
> Enable fast antenna diversity on devices with two RX chains
> (rx_mask == 3).  This programs the MULTICHAIN_GAIN_CTL register
> to configure main/alternate LNA settings and enables the
> CCK fast antenna diversity bit.
> 
> The AR9170 hardware has antenna diversity registers inherited
> from the AR9285/AR9287 family, but the carl9170 driver never
> programmed them.  For dual-chain devices this improves receive
> performance in multipath environments by allowing the baseband
> to quickly switch between antenna paths.

Oh, no. It does program them! It's part of the ar5416_phy_init array in phy.c.

So. From what I remember, this was the reason why I copied the definitions
over from the ath9k driver to carl9170. Because this register must be important
if they are part of the init values. But I don't know if these definitions
are the same for AR9170 and AR9285. That's why the AR9285 is there.

As for ar5416_phy_init values. They came from the original OTUS driver.

Hope this helps.

If possible, this feature should be governed by something like the experimental
module parameter?

> 
> The diversity configuration mirrors what ath9k uses for the
> AR9285 single-chip design:
> - Main LNA: LNA1
> - Alt LNA: LNA1+LNA2 (combined)
> - Gain table: table 0 for both paths
> 
> Signed-off-by: Masi Osmani <mas-i@hotmail.de>
> ---
>   drivers/net/wireless/ath/carl9170/phy.c | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/carl9170/phy.c b/drivers/net/wireless/ath/carl9170/phy.c
> index 290c336..bcd9066 100644
> --- a/drivers/net/wireless/ath/carl9170/phy.c
> +++ b/drivers/net/wireless/ath/carl9170/phy.c
> @@ -536,6 +536,31 @@ static int carl9170_init_phy_from_eeprom(struct ar9170 *ar,
>   	carl9170_regwrite(AR9170_PHY_REG_RX_CHAINMASK, ar->eeprom.rx_mask);
>   	carl9170_regwrite(AR9170_PHY_REG_CAL_CHAINMASK, ar->eeprom.rx_mask);
>   
> +	/*
> +	 * Enable fast antenna diversity for 2-chain devices.
> +	 * Configure main/alt LNA with both chains for best
> +	 * multipath performance.
> +	 */
> +	if (ar->eeprom.rx_mask == 3) {
> +		val = carl9170_def_val(AR9170_PHY_REG_MULTICHAIN_GAIN_CTL,
> +				       is_2ghz, is_40mhz);
> +		val |= AR9170_PHY_9285_ANT_DIV_CTL;
> +		SET_VAL(AR9170_PHY_9285_ANT_DIV_ALT_LNACONF, val,
> +			AR9170_PHY_9285_ANT_DIV_LNA1_PLUS_LNA2);
> +		SET_VAL(AR9170_PHY_9285_ANT_DIV_MAIN_LNACONF, val,
> +			AR9170_PHY_9285_ANT_DIV_LNA1);
> +		SET_VAL(AR9170_PHY_9285_ANT_DIV_ALT_GAINTB, val,
> +			AR9170_PHY_9285_ANT_DIV_GAINTB_0);
> +		SET_VAL(AR9170_PHY_9285_ANT_DIV_MAIN_GAINTB, val,
> +			AR9170_PHY_9285_ANT_DIV_GAINTB_0);
> +		carl9170_regwrite(AR9170_PHY_REG_MULTICHAIN_GAIN_CTL, val);
> +
> +		val = carl9170_def_val(AR9170_PHY_REG_CCK_DETECT,
> +				       is_2ghz, is_40mhz);
> +		val |= AR9170_PHY_CCK_DETECT_BB_ENABLE_ANT_FAST_DIV;
> +		carl9170_regwrite(AR9170_PHY_REG_CCK_DETECT, val);
> +	}
> +
>   	carl9170_regwrite_finish();
>   	return carl9170_regwrite_result();
>   }