ath9k_common: add new module to share 802.11n driver helpers

ath9k and ath9k_htc share a lot of common hardware characteristics.
They only differ in that ath9k_htc works with a target CPU and ath9k
works directly with the hardware. ath9k_htc will do *some* things in
the firmware, but a lot of others on the host.

The common 802.11n hardware code is already shared through the ath9k_hw
module. Common helpers amongst all Atheros drivers can use the ath module,
this includes ath5k and ar9170 as users. But there is some common driver
specific helpers which are not exactly hardware code which ath9k and
ath9k_htc can share. We'll be using ath9k_common for this to avoid
bloating the ath module and the common 802.11n hardware module ath9k_hw.

We start by sharing skb pre and post processing in preparation for a hand
off to mac80211.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 326 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath/ath9k/common.c b/drivers/net/wireless/ath/ath9k/common.c
new file mode 100644
index 000000000000..5fb164e294de
--- /dev/null
+++ b/drivers/net/wireless/ath/ath9k/common.c
@@ -0,0 +1,326 @@
+/*
+ * Copyright (c) 2009 Atheros Communications Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Module for common driver code between ath9k and ath9k_htc
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include "common.h"
+
+MODULE_AUTHOR("Atheros Communications");
+MODULE_DESCRIPTION("Shared library for Atheros wireless 802.11n LAN cards.");
+MODULE_LICENSE("Dual BSD/GPL");
+
+/* Common RX processing */
+
+/* Assumes you've already done the endian to CPU conversion */
+static bool ath9k_rx_accept(struct ath_common *common,
+                            struct sk_buff *skb,
+                            struct ieee80211_rx_status *rxs,
+                            struct ath_rx_status *rx_stats,
+                            bool *decrypt_error)
+{
+        struct ath_hw *ah = common->ah;
+        struct ieee80211_hdr *hdr;
+        __le16 fc;
+
+        hdr = (struct ieee80211_hdr *) skb->data;
+        fc = hdr->frame_control;
+
+        if (!rx_stats->rs_datalen)
+                return false;
+        /*
+         * rs_status follows rs_datalen so if rs_datalen is too large
+         * we can take a hint that hardware corrupted it, so ignore
+         * those frames.
+         */
+        if (rx_stats->rs_datalen > common->rx_bufsize)
+                return false;
+
+        if (rx_stats->rs_more) {
+                /*
+                 * Frame spans multiple descriptors; this cannot happen yet
+                 * as we don't support jumbograms. If not in monitor mode,
+                 * discard the frame. Enable this if you want to see
+                 * error frames in Monitor mode.
+                 */
+                if (ah->opmode != NL80211_IFTYPE_MONITOR)
+                        return false;
+        } else if (rx_stats->rs_status != 0) {
+                if (rx_stats->rs_status & ATH9K_RXERR_CRC)
+                        rxs->flag |= RX_FLAG_FAILED_FCS_CRC;
+                if (rx_stats->rs_status & ATH9K_RXERR_PHY)
+                        return false;
+
+                if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT) {
+                        *decrypt_error = true;
+                } else if (rx_stats->rs_status & ATH9K_RXERR_MIC) {
+                        if (ieee80211_is_ctl(fc))
+                                /*
+                                 * Sometimes, we get invalid
+                                 * MIC failures on valid control frames.
+                                 * Remove these mic errors.
+                                 */
+                                rx_stats->rs_status &= ~ATH9K_RXERR_MIC;
+                        else
+                                rxs->flag |= RX_FLAG_MMIC_ERROR;
+                }
+                /*
+                 * Reject error frames with the exception of
+                 * decryption and MIC failures. For monitor mode,
+                 * we also ignore the CRC error.
+                 */
+                if (ah->opmode == NL80211_IFTYPE_MONITOR) {
+                        if (rx_stats->rs_status &
+                            ~(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_MIC |
+                              ATH9K_RXERR_CRC))
+                                return false;
+                } else {
+                        if (rx_stats->rs_status &
+                            ~(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_MIC)) {
+                                return false;
+                        }
+                }
+        }
+        return true;
+}
+
+static u8 ath9k_process_rate(struct ath_common *common,
+                             struct ieee80211_hw *hw,
+                             struct ath_rx_status *rx_stats,
+                             struct ieee80211_rx_status *rxs,
+                             struct sk_buff *skb)
+{
+        struct ieee80211_supported_band *sband;
+        enum ieee80211_band band;
+        unsigned int i = 0;
+
+        band = hw->conf.channel->band;
+        sband = hw->wiphy->bands[band];
+
+        if (rx_stats->rs_rate & 0x80) {
+                /* HT rate */
+                rxs->flag |= RX_FLAG_HT;
+                if (rx_stats->rs_flags & ATH9K_RX_2040)
+                        rxs->flag |= RX_FLAG_40MHZ;
+                if (rx_stats->rs_flags & ATH9K_RX_GI)
+                        rxs->flag |= RX_FLAG_SHORT_GI;
+                return rx_stats->rs_rate & 0x7f;
+        }
+
+        for (i = 0; i < sband->n_bitrates; i++) {
+                if (sband->bitrates[i].hw_value == rx_stats->rs_rate)
+                        return i;
+                if (sband->bitrates[i].hw_value_short == rx_stats->rs_rate) {
+                        rxs->flag |= RX_FLAG_SHORTPRE;
+                        return i;
+                }
+        }
+
+        /* No valid hardware bitrate found -- we should not get here */
+        ath_print(common, ATH_DBG_XMIT, "unsupported hw bitrate detected "
+                  "0x%02x using 1 Mbit\n", rx_stats->rs_rate);
+        if ((common->debug_mask & ATH_DBG_XMIT))
+                print_hex_dump_bytes("", DUMP_PREFIX_NONE, skb->data, skb->len);
+
+        return 0;
+}
+
+/*
+ * Theory for reporting quality:
+ *
+ * At a hardware RSSI of 45 you will be able to use MCS 7  reliably.
+ * At a hardware RSSI of 45 you will be able to use MCS 15 reliably.
+ * At a hardware RSSI of 35 you should be able use 54 Mbps reliably.
+ *
+ * MCS 7  is the highets MCS index usable by a 1-stream device.
+ * MCS 15 is the highest MCS index usable by a 2-stream device.
+ *
+ * All ath9k devices are either 1-stream or 2-stream.
+ *
+ * How many bars you see is derived from the qual reporting.
+ *
+ * A more elaborate scheme can be used here but it requires tables
+ * of SNR/throughput for each possible mode used. For the MCS table
+ * you can refer to the wireless wiki:
+ *
+ * http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n
+ *
+ */
+static int ath9k_compute_qual(struct ieee80211_hw *hw,
+                              struct ath_rx_status *rx_stats)
+{
+        int qual;
+
+        if (conf_is_ht(&hw->conf))
+                qual =  rx_stats->rs_rssi * 100 / 45;
+        else
+                qual =  rx_stats->rs_rssi * 100 / 35;
+
+        /*
+         * rssi can be more than 45 though, anything above that
+         * should be considered at 100%
+         */
+        if (qual > 100)
+                qual = 100;
+
+        return qual;
+}
+
+static void ath9k_process_rssi(struct ath_common *common,
+                               struct ieee80211_hw *hw,
+                               struct sk_buff *skb,
+                               struct ath_rx_status *rx_stats)
+{
+        struct ath_hw *ah = common->ah;
+        struct ieee80211_sta *sta;
+        struct ieee80211_hdr *hdr;
+        struct ath_node *an;
+        int last_rssi = ATH_RSSI_DUMMY_MARKER;
+        __le16 fc;
+
+        hdr = (struct ieee80211_hdr *)skb->data;
+        fc = hdr->frame_control;
+
+        rcu_read_lock();
+        /*
+         * XXX: use ieee80211_find_sta! This requires quite a bit of work
+         * under the current ath9k virtual wiphy implementation as we have
+         * no way of tying a vif to wiphy. Typically vifs are attached to
+         * at least one sdata of a wiphy on mac80211 but with ath9k virtual
+         * wiphy you'd have to iterate over every wiphy and each sdata.
+         */
+        sta = ieee80211_find_sta_by_hw(hw, hdr->addr2);
+        if (sta) {
+                an = (struct ath_node *) sta->drv_priv;
+                if (rx_stats->rs_rssi != ATH9K_RSSI_BAD &&
+                   !rx_stats->rs_moreaggr)
+                        ATH_RSSI_LPF(an->last_rssi, rx_stats->rs_rssi);
+                last_rssi = an->last_rssi;
+        }
+        rcu_read_unlock();
+
+        if (likely(last_rssi != ATH_RSSI_DUMMY_MARKER))
+                rx_stats->rs_rssi = ATH_EP_RND(last_rssi,
+                                              ATH_RSSI_EP_MULTIPLIER);
+        if (rx_stats->rs_rssi < 0)
+                rx_stats->rs_rssi = 0;
+        else if (rx_stats->rs_rssi > 127)
+                rx_stats->rs_rssi = 127;
+
+        /* Update Beacon RSSI, this is used by ANI. */
+        if (ieee80211_is_beacon(fc))
+                ah->stats.avgbrssi = rx_stats->rs_rssi;
+}
+
+/*
+ * For Decrypt or Demic errors, we only mark packet status here and always push
+ * up the frame up to let mac80211 handle the actual error case, be it no
+ * decryption key or real decryption error. This let us keep statistics there.
+ */
+int ath9k_cmn_rx_skb_preprocess(struct ath_common *common,
+                                struct ieee80211_hw *hw,
+                                struct sk_buff *skb,
+                                struct ath_rx_status *rx_stats,
+                                struct ieee80211_rx_status *rx_status,
+                                bool *decrypt_error)
+{
+        struct ath_hw *ah = common->ah;
+
+        if (!ath9k_rx_accept(common, skb, rx_status, rx_stats, decrypt_error))
+                return -EINVAL;
+
+        ath9k_process_rssi(common, hw, skb, rx_stats);
+
+        rx_status->rate_idx = ath9k_process_rate(common, hw,
+                                                 rx_stats, rx_status, skb);
+        rx_status->mactime = ath9k_hw_extend_tsf(ah, rx_stats->rs_tstamp);
+        rx_status->band = hw->conf.channel->band;
+        rx_status->freq = hw->conf.channel->center_freq;
+        rx_status->noise = common->ani.noise_floor;
+        rx_status->signal = ATH_DEFAULT_NOISE_FLOOR + rx_stats->rs_rssi;
+        rx_status->antenna = rx_stats->rs_antenna;
+        rx_status->qual = ath9k_compute_qual(hw, rx_stats);
+        rx_status->flag |= RX_FLAG_TSFT;
+
+        return 0;
+}
+EXPORT_SYMBOL(ath9k_cmn_rx_skb_preprocess);
+
+void ath9k_cmn_rx_skb_postprocess(struct ath_common *common,
+                                  struct sk_buff *skb,
+                                  struct ath_rx_status *rx_stats,
+                                  struct ieee80211_rx_status *rxs,
+                                  bool decrypt_error)
+{
+        struct ath_hw *ah = common->ah;
+        struct ieee80211_hdr *hdr;
+        int hdrlen, padsize;
+        u8 keyix;
+        __le16 fc;
+
+        /* see if any padding is done by the hw and remove it */
+        hdr = (struct ieee80211_hdr *) skb->data;
+        hdrlen = ieee80211_get_hdrlen_from_skb(skb);
+        fc = hdr->frame_control;
+
+        /* The MAC header is padded to have 32-bit boundary if the
+         * packet payload is non-zero. The general calculation for
+         * padsize would take into account odd header lengths:
+         * padsize = (4 - hdrlen % 4) % 4; However, since only
+         * even-length headers are used, padding can only be 0 or 2
+         * bytes and we can optimize this a bit. In addition, we must
+         * not try to remove padding from short control frames that do
+         * not have payload. */
+        padsize = hdrlen & 3;
+        if (padsize && hdrlen >= 24) {
+                memmove(skb->data + padsize, skb->data, hdrlen);
+                skb_pull(skb, padsize);
+        }
+
+        keyix = rx_stats->rs_keyix;
+
+        if (!(keyix == ATH9K_RXKEYIX_INVALID) && !decrypt_error) {
+                rxs->flag |= RX_FLAG_DECRYPTED;
+        } else if (ieee80211_has_protected(fc)
+                   && !decrypt_error && skb->len >= hdrlen + 4) {
+                keyix = skb->data[hdrlen + 3] >> 6;
+
+                if (test_bit(keyix, common->keymap))
+                        rxs->flag |= RX_FLAG_DECRYPTED;
+        }
+        if (ah->sw_mgmt_crypto &&
+            (rxs->flag & RX_FLAG_DECRYPTED) &&
+            ieee80211_is_mgmt(fc))
+                /* Use software decrypt for management frames. */
+                rxs->flag &= ~RX_FLAG_DECRYPTED;
+}
+EXPORT_SYMBOL(ath9k_cmn_rx_skb_postprocess);
+
+static int __init ath9k_cmn_init(void)
+{
+        return 0;
+}
+module_init(ath9k_cmn_init);
+
+static void __exit ath9k_cmn_exit(void)
+{
+        return;
+}
+module_exit(ath9k_cmn_exit);