Re: WARNING at net/mac80211/rate.c:513 ieee80211_get_tx_rates [mac80211]

[Larry Finger <Larry.Finger@lwfinger.net>]

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Linus,

Attached is a trial patch that fixes the problem on my system. As I told 
Johannes earlier, my AP was not configured to use VHT, thus I did not see the 
problem.

The test patch that Johannes sent earlier was close. The section needed to add 
VHT rates is:

--- a/drivers/net/wireless/realtek/rtlwifi/rc.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rc.c
@@ -138,6 +138,9 @@ static void _rtl_rc_rate_set_series(struct rtl_priv *rtlpriv,
                     ((wireless_mode == WIRELESS_MODE_N_5G) ||
                      (wireless_mode == WIRELESS_MODE_N_24G)))
                         rate->flags |= IEEE80211_TX_RC_MCS;
+               if (sta && sta->vht_cap.vht_supported &&
+                   (wireless_mode == WIRELESS_MODE_AC_5G))
+                       rate->flags |= IEEE80211_TX_RC_VHT_MCS;
         }
  }

Larry


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>From bd34ac0c3caa9ff982194256b0e96772a17e719d Mon Sep 17 00:00:00 2001
From: Larry Finger <Larry.Finger@lwfinger.net>
Date: Fri, 29 Jan 2016 11:29:10 -0600
Subject: [PATCH] rtlwifi: Fix warning from ieee80211_get_tx_rates() when using
 5G
To: kvalo@codeaurora.org
Cc: linux-wireless@vger.kernel.org,
    devel@driverdev.osuosl.org

When using a 5G-capable device with VHT rates enabled, the following
warning results:

WARNING: CPU: 3 PID: 2253 at net/mac80211/rate.c:625 ieee80211_get_tx_rates+0x22e/0x620 [mac80211]()
Modules linked in: rtl8821ae btcoexist rtl_pci rtlwifi fuse drbg ansi_cprng ctr ccm bnep bluetooth af_packet nfs fscache vboxpci(O) vboxnetadp(O) vboxne
tflt(O) vboxdrv(O) arc4 snd_hda_codec_generic x86_pkg_temp_thermal rtsx_pci_sdmmc mmc_core rtsx_pci_ms kvm_intel memstick iwlmvm kvm mac80211 snd_hda_intel snd_hda_cod
ec snd_hwdep snd_hda_core irqbypass snd_pcm iwlwifi crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 snd_timer lrw gf128mul glue_h
elper ablk_helper cryptd snd cfg80211 pcspkr serio_raw e1000e rtsx_pci lpc_ich ptp xhci_pci mfd_core pps_core xhci_hcd soundcore toshiba_acpi thermal sparse_keymap wmi
 toshiba_bluetooth rfkill acpi_cpufreq battery ac processor dm_mod i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops
drm sr_mod cdrom video button sg autofs4 [last unloaded: rtlwifi]
CPU: 3 PID: 2253 Comm: Timer Tainted: G        W  O    4.5.0-rc1-wl+ #79
Hardware name: TOSHIBA TECRA A50-A/TECRA A50-A, BIOS Version 4.20   04/17/2014
  ffffffffa05c4be6 ffff8802262036d8 ffffffff813d7912 0000000000000000
  ffff880226203710 ffffffff8106bcb6 ffff8800c6831300 ffff8800c6831330
  0000000000000000 ffff8800c683133c ffff880065923638 ffff880226203720
Call Trace:
  <IRQ>  [<ffffffff813d7912>] dump_stack+0x4b/0x79
  [<ffffffff8106bcb6>] warn_slowpath_common+0x86/0xc0
  [<ffffffff8106bdaa>] warn_slowpath_null+0x1a/0x20
  [<ffffffffa05511ee>] ieee80211_get_tx_rates+0x22e/0x620 [mac80211]
  [<ffffffffa0782232>] ? rtl_is_special_data+0x32/0x240 [rtlwifi]
  [<ffffffffa055209e>] ? rate_control_get_rate+0xce/0x150 [mac80211]
  [<ffffffff810bfc7d>] ? trace_hardirqs_on+0xd/0x10
  [<ffffffff81071cc5>] ? __local_bh_enable_ip+0x65/0xd0
--- traceback terminated here ---

The problem is that IEEE80211_TX_RC_VHT_MCS is not set in the rate flags.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
---
 drivers/net/wireless/realtek/rtlwifi/rc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtlwifi/rc.c b/drivers/net/wireless/realtek/rtlwifi/rc.c
index 74c14ce..e7eae63 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rc.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rc.c
@@ -138,6 +138,9 @@ static void _rtl_rc_rate_set_series(struct rtl_priv *rtlpriv,
 		    ((wireless_mode == WIRELESS_MODE_N_5G) ||
 		     (wireless_mode == WIRELESS_MODE_N_24G)))
 			rate->flags |= IEEE80211_TX_RC_MCS;
+		if (sta && sta->vht_cap.vht_supported &&
+		    (wireless_mode == WIRELESS_MODE_AC_5G))
+			rate->flags |= IEEE80211_TX_RC_VHT_MCS;
 	}
 }
 
-- 
2.1.4