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Date:   Wed, 4 Nov 2020 15:11:28 -0800
From:   Brian Norris <briannorris@chromium.org>
To:     Carl Huang <cjhuang@codeaurora.org>
Cc:     ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
        dianders@chromium.org, kuabhs@google.com
Subject: Re: [RFC 2/2] ath10k: allow dynamic SAR power limits via common API
Message-ID: <20201104231128.GA3212577@google.com>
References: <1600753775-4745-1-git-send-email-cjhuang@codeaurora.org>
 <1600753775-4745-2-git-send-email-cjhuang@codeaurora.org>
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Hi,

On Tue, Sep 22, 2020 at 01:49:35PM +0800, Carl Huang wrote:
> ath10k assigns ath10k_mac_set_sar_specs to ath10k_ops, and
> this function is called when user space application calls
> NL80211_CMD_SET_SAR_SPECS. ath10k also registers SAR type,
> and supported frequency ranges to wiphy so user space can
> query SAR capabilities.
> 
> ath10k_mac_set_sar_specs further sets the power to firmware
> to limit the TX power.
> 
> This feature is controlled by hw parameter: dynamic_sar_support.
> 
> Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
> ---

> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
> index 2e3eb5b..830c61f 100644
> --- a/drivers/net/wireless/ath/ath10k/mac.c
> +++ b/drivers/net/wireless/ath/ath10k/mac.c
> @@ -81,6 +81,17 @@ static struct ieee80211_rate ath10k_rates_rev2[] = {
>  	{ .bitrate = 540, .hw_value = ATH10K_HW_RATE_OFDM_54M },
>  };
>  
> +static const struct cfg80211_sar_freq_ranges ath10k_sar_freq_ranges[] = {
> +	{ .index = 0, .start_freq = 2412000, .end_freq = 2484000 },

2412 MHz is a center frequency, but other parts of the nl80211 API use
band edges. For example:

 * @NL80211_ATTR_FREQ_RANGE_START: starting frequencry for the regulatory
 *      rule in KHz. This is not a center of frequency but an actual regulatory
 *      band edge.
 * @NL80211_ATTR_FREQ_RANGE_END: ending frequency for the regulatory rule
 *      in KHz. This is not a center a frequency but an actual regulatory
 *      band edge.

Seems like we should improve the nl80211.h docs (patch 1) and make these
edges (this patch).

> +	{ .index = 1, .start_freq = 2484000, .end_freq = 5865000 },
> +};
> +
> +static const struct cfg80211_sar_capa ath10k_sar_capa = {
> +	.type = NL80211_SAR_TYPE_POWER,
> +	.num_freq_ranges = (ARRAY_SIZE(ath10k_sar_freq_ranges)),
> +	.freq_ranges = &ath10k_sar_freq_ranges[0],
> +};
> +
>  #define ATH10K_MAC_FIRST_OFDM_RATE_IDX 4
>  
>  #define ath10k_a_rates (ath10k_rates + ATH10K_MAC_FIRST_OFDM_RATE_IDX)
> @@ -2880,6 +2891,95 @@ static int ath10k_mac_vif_recalc_txbf(struct ath10k *ar,
>  	return 0;
>  }
>  
> +static bool ath10k_mac_is_connected(struct ath10k *ar)
> +{
> +	struct ath10k_vif *arvif;
> +
> +	list_for_each_entry(arvif, &ar->arvifs, list) {
> +		if (arvif->is_up && arvif->vdev_type == WMI_VDEV_TYPE_STA)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +int ath10k_mac_set_sar_power(struct ath10k *ar)

This function should be static.

> +{
> +	int ret;
> +
> +	if (!ar->hw_params.dynamic_sar_support)
> +		return 0;

return -EOPNOTSUPP ?

> +
> +	if (ar->tx_power_2g_limit == 0 || ar->tx_power_5g_limit == 0)

ath10k_mac_txpower_recalc() doesn't care about this -- why should you?
This also seems especially weird, because one of the 2 could be valid
nonzero values, and yet you're silently rejecting it. Regardless, the
following seems wrong:

> +		return 0;

This should probably be an error.

> +
> +	if (!ath10k_mac_is_connected(ar))
> +		return 0;

Note to self (since this wasn't obvious to me the first read-through):
you're calling this function from ath10k_bss_assoc() too, so even if you
weren't connected the first time around, it'll get called later.

> +
> +	ret = ath10k_wmi_pdev_set_param(ar,
> +					ar->wmi.pdev_param->txpower_limit2g,
> +					ar->tx_power_2g_limit);
> +	if (ret) {
> +		ath10k_warn(ar, "failed to set 2.4G txpower %d: %d\n",
> +			    ar->tx_power_2g_limit, ret);
> +		return ret;
> +	}
> +
> +	ret = ath10k_wmi_pdev_set_param(ar,
> +					ar->wmi.pdev_param->txpower_limit5g,
> +					ar->tx_power_5g_limit);
> +	if (ret) {
> +		ath10k_warn(ar, "failed to set 5G txpower %d: %d\n",
> +			    ar->tx_power_5g_limit, ret);
> +		return ret;
> +	}

Hmm, so these are the same params configured by
ath10k_mac_txpower_recalc(), except that we're not taking into account
the limitations in ath10k_mac_txpower_recalc() (and vice versa) -- isn't
that bad? Should we be merging the SAR limitation into
ath10k_mac_txpower_recalc() and calling that instead?

Brian

> +
> +	ath10k_dbg(ar, ATH10K_DBG_MAC, "set txpower 2G:%d, 5G:%d successfully\n",
> +		   ar->tx_power_2g_limit, ar->tx_power_5g_limit);
> +
> +	return ret;
> +}
> +