Dear Bob, Another patch of ath5k FYI.
Sincerely,
Forrest
----- Original Message -----
From: "Bob Copeland" <m...@bobcopeland.com>
To: <ath5k-devel@lists.ath5k.org>
Cc: "Nick Kossifidis" <mickfl...@gmail.com>; <forr...@263.net>
Sent: Tuesday, May 12, 2009 10:46 PM
Subject: RFC phy timing register bug
> Hi all,
>
> Someone pointed out to me a change in the code with the reset rework,
> due to my suggestion to use get_bitmask_order() which actually returns
> highest bit set+1. Nick, can you comment whether the patch below does
> the right thing and that the original code was correct?
>
> [Forrest, is this idea via you, and may I attribute you as the patch
> author like so?
>
> From: Forrest Zhang <your preferred email>]
>
> Here's a C program I used to confirm the problem (f1 is original code,
> f2 is get_bitmask_order with generic fls(). Output is:
>
> 1: 0 1
> 0: 0 0
> 32767: 14 15
> 65535: 15 16
> 65536: 16 17
> 1048576: 20 21
>
> --- start ---
> #include <inttypes.h>
> #include <stdio.h>
>
> static int fls(int x)
> {
> int r = 32;
>
> if (!x)
> return 0;
> if (!(x & 0xffff0000u)) {
> x <<= 16;
> r -= 16;
> }
> if (!(x & 0xff000000u)) {
> x <<= 8;
> r -= 8;
> }
> if (!(x & 0xf0000000u)) {
> x <<= 4;
> r -= 4;
> }
> if (!(x & 0xc0000000u)) {
> x <<= 2;
> r -= 2;
> }
> if (!(x & 0x80000000u)) {
> x <<= 1;
> r -= 1;
> }
> return r;
> }
>
> int f1(int c)
> {
> int bit;
> for (bit = 31; bit > 0; bit--)
> if ((c >> bit) & 1)
> break;
>
> return bit;
> }
>
> int f2(int c)
> {
> return fls(c);
> }
>
> int main()
> {
> int i;
> int nums[] = { 1, 0, 32767, 65535, 65536, 1048576 };
>
> for (i=0; i < sizeof(nums)/sizeof(int); i++)
> printf("%d: %d %d\n", nums[i], f1(nums[i]), f2(nums[i]));
>
> return 0;
> }
> --- end ---
>
> From d668403b04487a90378fc4ec7cd1ebe1e4b7bfe1 Mon Sep 17 00:00:00 2001
> From: Bob Copeland <m...@bobcopeland.com>
> Date: Tue, 12 May 2009 09:40:37 -0400
> Subject: [PATCH] ath5k: fix off-by-one when computing OFDM delta slope
>
> get_bitmask_order() actually returns the highest bit set plus one,
> whereas the previous code wanted the highest bit set. Also change
> type of coef_exp to int to deal with degenerate case of
> coef_exp == 0.
> ---
> drivers/net/wireless/ath/ath5k/reset.c | 8 ++++----
> 1 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath5k/reset.c
> b/drivers/net/wireless/ath/ath5k/reset.c
> index 4a2d93e..cc75e77 100644
> --- a/drivers/net/wireless/ath/ath5k/reset.c
> +++ b/drivers/net/wireless/ath/ath5k/reset.c
> @@ -51,8 +51,8 @@ static inline int ath5k_hw_write_ofdm_timings(struct
> ath5k_hw *ah,
> struct ieee80211_channel *channel)
> {
> /* Get exponent and mantissa and set it */
> - u32 coef_scaled, coef_exp, coef_man,
> - ds_coef_exp, ds_coef_man, clock;
> + u32 coef_scaled, coef_man, ds_coef_exp, ds_coef_man, clock;
> + int coef_exp;
>
> if (!(ah->ah_version == AR5K_AR5212) ||
> !(channel->hw_value & CHANNEL_OFDM))
> @@ -69,10 +69,10 @@ static inline int ath5k_hw_write_ofdm_timings(struct
> ath5k_hw *ah,
>
> /* Get exponent
> * ALGO: coef_exp = 14 - highest set bit position */
> - coef_exp = get_bitmask_order(coef_scaled);
> + coef_exp = get_bitmask_order(coef_scaled) - 1;
>
> /* Doesn't make sense if it's zero*/
> - if (!coef_exp)
> + if (coef_exp <= 0)
> return -EINVAL;
>
> /* Note: we've shifted coef_scaled by 24 */
> --
> 1.6.0.6
>
>
> --
> Bob Copeland %% www.bobcopeland.com
>
>
>
40_linux-2.6.30-rc6_ath5k_eeprom.patch
Description: Binary data
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