The brcm80211 driver in the staging tree has a cordic function to
determine cosine and sine for a given angle. Feedback received from
John Linville suggested that these kind of functions should be made
available to others as a library function in the kernel tree.
V1:
- code taken from brcm80211 driver and added kernel-doc comments.
- code compiled and tested for x86 architecture using brcm80211 driver.
- code compiled for x86_64, ARM, and MIPS architectures.
Cc: [email protected]
Cc: [email protected]
Cc: "John W. Linville" <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Dan Carpenter <[email protected]>
Reviewed-by: Roland Vossen <[email protected]>
Reviewed-by: Henry Ptasinski <[email protected]>
Reviewed-by: Franky (Zhenhui) Lin <[email protected]>
Signed-off-by: Arend van Spriel <[email protected]>
---
include/linux/cordic.h | 48 +++++++++++++++++++++++
lib/Kconfig | 7 +++
lib/Makefile | 2 +
lib/cordic.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 156 insertions(+), 0 deletions(-)
create mode 100644 include/linux/cordic.h
create mode 100644 lib/cordic.c
diff --git a/include/linux/cordic.h b/include/linux/cordic.h
new file mode 100644
index 0000000..28443a6
--- /dev/null
+++ b/include/linux/cordic.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2011 Broadcom Corporation
+ *
+ * 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.
+ */
+#ifndef __CORDIC_H_
+#define __CORDIC_H_
+
+#include <linux/types.h>
+
+/**
+ * struct - i/q coordinate.
+ *
+ * @i: real part of coordinate (in phase).
+ * @q: imaginary part of coordinate (quadrature).
+ */
+struct cordic_iq {
+ s32 i;
+ s32 q;
+};
+
+/**
+ * cordic_calc_iq() - calculates the i/q coordinate for given angle.
+ *
+ * @theta: angle in degrees for which i/q coordinate is to be calculated.
+ * @coord: function output parameter holding the i/q coordinate.
+ *
+ * The function calculates the i/q coordinate for a given angle using
+ * cordic algorithm. The coordinate consists of a real (i) and an
+ * imaginary (q) part. The real part is essentially the cosine of the
+ * angle and the imaginary part is the sine of the angle. The returned
+ * values are scaled by 2^16 for precision. The range for theta is
+ * for -180 degrees to +180 degrees. Passed values outside this range are
+ * converted before doing the actual calculation.
+ */
+void cordic_calc_iq(s32 theta, struct cordic_iq *coord);
+
+#endif /* __CORDIC_H_ */
diff --git a/lib/Kconfig b/lib/Kconfig
index ff9e5a3..5c70204 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -279,4 +279,11 @@ config AVERAGE
If unsure, say N.
+config CORDIC
+ tristate "Cordic function"
+ help
+ The option provides arithmetic function using cordic algorithm
+ so its calculations are in fixed point. Modules can select this
+ when they require this function. Module will be called cordic.
+
endmenu
diff --git a/lib/Makefile b/lib/Makefile
index 704959d..9e3c1b0 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -117,6 +117,8 @@ obj-$(CONFIG_AVERAGE) += average.o
obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
+obj-$(CONFIG_CORDIC) += cordic.o
+
hostprogs-y := gen_crc32table
clean-files := crc32table.h
diff --git a/lib/cordic.c b/lib/cordic.c
new file mode 100644
index 0000000..3952258
--- /dev/null
+++ b/lib/cordic.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2011 Broadcom Corporation
+ *
+ * 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.
+ */
+#include <linux/module.h>
+#include <linux/cordic.h>
+
+#define CORDIC_ANGLE_GEN 39797
+#define CORDIC_PRECISION_SHIFT 16
+#define CORDIC_NUM_ITER (CORDIC_PRECISION_SHIFT + 2)
+
+#define FIXED(X) ((s32)((X) << CORDIC_PRECISION_SHIFT))
+#define FLOAT(X) (((X) >= 0) \
+ ? ((((X) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1) \
+ : -((((-(X)) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1))
+
+static const s32 AtanTbl[] = {
+ 2949120,
+ 1740967,
+ 919879,
+ 466945,
+ 234379,
+ 117304,
+ 58666,
+ 29335,
+ 14668,
+ 7334,
+ 3667,
+ 1833,
+ 917,
+ 458,
+ 229,
+ 115,
+ 57,
+ 29
+};
+
+/*
+ * cordic_calc_iq() - calculates the i/q coordinate for given angle
+ *
+ * theta: angle in degrees for which i/q coordinate is to be calculated
+ * coord: function output parameter holding the i/q coordinate
+ */
+void cordic_calc_iq(s32 theta, struct cordic_iq *coord)
+{
+ s32 angle, valtmp;
+ unsigned iter;
+ int signx = 1;
+ int signtheta;
+
+ coord->i = CORDIC_ANGLE_GEN;
+ coord->q = 0;
+ angle = 0;
+
+ theta = FIXED(theta);
+ signtheta = (theta < 0) ? -1 : 1;
+ theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) -
+ FIXED(180) * signtheta;
+
+ if (FLOAT(theta) > 90) {
+ theta -= FIXED(180);
+ signx = -1;
+ } else if (FLOAT(theta) < -90) {
+ theta += FIXED(180);
+ signx = -1;
+ }
+
+ for (iter = 0; iter < CORDIC_NUM_ITER; iter++) {
+ if (theta > angle) {
+ valtmp = coord->i - (coord->q >> iter);
+ coord->q += (coord->i >> iter);
+ angle += AtanTbl[iter];
+ } else {
+ valtmp = coord->i + (coord->q >> iter);
+ coord->q -= (coord->i >> iter);
+ angle -= AtanTbl[iter];
+ }
+ coord->i = valtmp;
+ }
+
+ coord->i *= signx;
+ coord->q *= signx;
+}
+EXPORT_SYMBOL(cordic_calc_iq);
+
+MODULE_DESCRIPTION("Cordic functions");
+MODULE_AUTHOR("Broadcom Corporation");
+MODULE_LICENSE("Dual BSD/GPL");
--
1.7.4.1
On Wed, 25 May 2011 21:40:26 +0200 Arend van Spriel wrote:
> diff --git a/include/linux/cordic.h b/include/linux/cordic.h
> new file mode 100644
> index 0000000..28443a6
> --- /dev/null
> +++ b/include/linux/cordic.h
> @@ -0,0 +1,48 @@
> +/**
> + * struct - i/q coordinate.
* struct cordic_iq - i/q coordinate
> + *
> + * @i: real part of coordinate (in phase).
> + * @q: imaginary part of coordinate (quadrature).
> + */
> +struct cordic_iq {
> + s32 i;
> + s32 q;
> +};
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
On 05/25/2011 02:40 PM, Arend van Spriel wrote:
> The brcm80211 driver in the staging tree has a cordic function to
> determine cosine and sine for a given angle. Feedback received from
> John Linville suggested that these kind of functions should be made
> available to others as a library function in the kernel tree.
>
> V1:
> - code taken from brcm80211 driver and added kernel-doc comments.
> - code compiled and tested for x86 architecture using brcm80211 driver.
> - code compiled for x86_64, ARM, and MIPS architectures.
>
> Cc: [email protected]
> Cc: [email protected]
> Cc: "John W. Linville"<[email protected]>
> Cc: Greg Kroah-Hartman<[email protected]>
> Cc: Dan Carpenter<[email protected]>
> Reviewed-by: Roland Vossen<[email protected]>
> Reviewed-by: Henry Ptasinski<[email protected]>
> Reviewed-by: Franky (Zhenhui) Lin<[email protected]>
> Signed-off-by: Arend van Spriel<[email protected]>
> ---
> include/linux/cordic.h | 48 +++++++++++++++++++++++
> lib/Kconfig | 7 +++
> lib/Makefile | 2 +
> lib/cordic.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 156 insertions(+), 0 deletions(-)
> create mode 100644 include/linux/cordic.h
> create mode 100644 lib/cordic.c
There is a similar routine in b43, thus this library function will likely have
at least 2 users.
> diff --git a/include/linux/cordic.h b/include/linux/cordic.h
> new file mode 100644
> index 0000000..28443a6
> --- /dev/null
> +++ b/include/linux/cordic.h
> @@ -0,0 +1,48 @@
> +/*
> + * Copyright (c) 2011 Broadcom Corporation
> + *
> + * 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.
> + */
> +#ifndef __CORDIC_H_
> +#define __CORDIC_H_
> +
> +#include<linux/types.h>
> +
> +/**
> + * struct - i/q coordinate.
> + *
> + * @i: real part of coordinate (in phase).
> + * @q: imaginary part of coordinate (quadrature).
> + */
> +struct cordic_iq {
> + s32 i;
> + s32 q;
> +};
> +
> +/**
> + * cordic_calc_iq() - calculates the i/q coordinate for given angle.
> + *
> + * @theta: angle in degrees for which i/q coordinate is to be calculated.
> + * @coord: function output parameter holding the i/q coordinate.
> + *
> + * The function calculates the i/q coordinate for a given angle using
> + * cordic algorithm. The coordinate consists of a real (i) and an
> + * imaginary (q) part. The real part is essentially the cosine of the
> + * angle and the imaginary part is the sine of the angle. The returned
> + * values are scaled by 2^16 for precision. The range for theta is
> + * for -180 degrees to +180 degrees. Passed values outside this range are
> + * converted before doing the actual calculation.
> + */
> +void cordic_calc_iq(s32 theta, struct cordic_iq *coord);
> +
> +#endif /* __CORDIC_H_ */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index ff9e5a3..5c70204 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -279,4 +279,11 @@ config AVERAGE
>
> If unsure, say N.
>
> +config CORDIC
> + tristate "Cordic function"
> + help
> + The option provides arithmetic function using cordic algorithm
> + so its calculations are in fixed point. Modules can select this
> + when they require this function. Module will be called cordic.
> +
> endmenu
> diff --git a/lib/Makefile b/lib/Makefile
> index 704959d..9e3c1b0 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -117,6 +117,8 @@ obj-$(CONFIG_AVERAGE) += average.o
>
> obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
>
> +obj-$(CONFIG_CORDIC) += cordic.o
> +
> hostprogs-y := gen_crc32table
> clean-files := crc32table.h
>
> diff --git a/lib/cordic.c b/lib/cordic.c
> new file mode 100644
> index 0000000..3952258
> --- /dev/null
> +++ b/lib/cordic.c
> @@ -0,0 +1,99 @@
> +/*
> + * Copyright (c) 2011 Broadcom Corporation
> + *
> + * 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.
> + */
> +#include<linux/module.h>
> +#include<linux/cordic.h>
> +
> +#define CORDIC_ANGLE_GEN 39797
> +#define CORDIC_PRECISION_SHIFT 16
> +#define CORDIC_NUM_ITER (CORDIC_PRECISION_SHIFT + 2)
> +
> +#define FIXED(X) ((s32)((X)<< CORDIC_PRECISION_SHIFT))
> +#define FLOAT(X) (((X)>= 0) \
> + ? ((((X)>> (CORDIC_PRECISION_SHIFT - 1)) + 1)>> 1) \
> + : -((((-(X))>> (CORDIC_PRECISION_SHIFT - 1)) + 1)>> 1))
> +
> +static const s32 AtanTbl[] = {
In Documentation/CodingStyle, variables with mixed-case names are frownid upon.
> + 2949120,
> + 1740967,
> + 919879,
> + 466945,
> + 234379,
> + 117304,
> + 58666,
> + 29335,
> + 14668,
> + 7334,
> + 3667,
> + 1833,
> + 917,
> + 458,
> + 229,
> + 115,
> + 57,
> + 29
> +};
> +
> +/*
> + * cordic_calc_iq() - calculates the i/q coordinate for given angle
> + *
> + * theta: angle in degrees for which i/q coordinate is to be calculated
> + * coord: function output parameter holding the i/q coordinate
> + */
> +void cordic_calc_iq(s32 theta, struct cordic_iq *coord)
As "coord" is only for output, why not have this be a function returning a
struct cordic_iq?
> +{
> + s32 angle, valtmp;
> + unsigned iter;
> + int signx = 1;
> + int signtheta;
> +
> + coord->i = CORDIC_ANGLE_GEN;
> + coord->q = 0;
> + angle = 0;
> +
> + theta = FIXED(theta);
> + signtheta = (theta< 0) ? -1 : 1;
> + theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) -
> + FIXED(180) * signtheta;
> +
> + if (FLOAT(theta)> 90) {
> + theta -= FIXED(180);
> + signx = -1;
> + } else if (FLOAT(theta)< -90) {
> + theta += FIXED(180);
> + signx = -1;
> + }
> +
> + for (iter = 0; iter< CORDIC_NUM_ITER; iter++) {
> + if (theta> angle) {
> + valtmp = coord->i - (coord->q>> iter);
I think the whitespace should be the same on both sides of the >> operator.
Either "coord->q>>iter" or "coord->q >> iter" would be OK. I know checkpatch.pl
does not complain, but it does for other binary operators.
> + coord->q += (coord->i>> iter);
> + angle += AtanTbl[iter];
> + } else {
> + valtmp = coord->i + (coord->q>> iter);
> + coord->q -= (coord->i>> iter);
> + angle -= AtanTbl[iter];
> + }
> + coord->i = valtmp;
> + }
> +
> + coord->i *= signx;
> + coord->q *= signx;
> +}
> +EXPORT_SYMBOL(cordic_calc_iq);
> +
> +MODULE_DESCRIPTION("Cordic functions");
> +MODULE_AUTHOR("Broadcom Corporation");
> +MODULE_LICENSE("Dual BSD/GPL");
Larry
On 05/26/2011 10:09 AM, Arend van Spriel wrote:
> On 05/25/2011 10:04 PM, Randy Dunlap wrote:
>> On Wed, 25 May 2011 21:40:26 +0200 Arend van Spriel wrote:
>>> +/**
>>> + * struct - i/q coordinate.
>> * struct cordic_iq - i/q coordinate
> The kernel-doc processing is pretty smart here. In the current form I
> get the html as attached. From that perspective your proposed change is
> not needed, but if your point is that it would be more clear to the mere
> mortal reading through the source code I can change it.
>
> Gr. AvS
Attached html does not get through the mail server. So here is part of
the html source:
<h2>struct cordic_iq - i/q coordinate.</h2>
<b>struct cordic_iq</b> {<br>
<i>s32</i> <b>i</b>;<br>
<i>s32</i> <b>q</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>i</b>
<dd>real part of coordinate (in phase).
<dt><b>q</b>
<dd>imaginary part of coordinate (quadrature).
</dl>
Gr. AvS
--
Almost nobody dances sober, unless they happen to be insane.
-- H.P. Lovecraft --
On 05/25/2011 10:35 PM, Larry Finger wrote:
> On 05/25/2011 02:40 PM, Arend van Spriel wrote:
>> The brcm80211 driver in the staging tree has a cordic function to
>> determine cosine and sine for a given angle. Feedback received from
>> John Linville suggested that these kind of functions should be made
>> available to others as a library function in the kernel tree.
> There is a similar routine in b43, thus this library function will likely have
> at least 2 users.
I know (forgot to mention it in the commit message). Henry Ptasinski
(broadcom colleague) actually verified both functions against Matlab
implementation (or Scilab, if you prefer open-source ;-) ). The b43
version has a more limited range of the angle input in which the
calculation is accurate.
>> +static const s32 AtanTbl[] = {
> In Documentation/CodingStyle, variables with mixed-case names are frownid upon.
No frowning needed. I will change it ;-)
>
>> +/*
>> + * cordic_calc_iq() - calculates the i/q coordinate for given angle
>> + *
>> + * theta: angle in degrees for which i/q coordinate is to be calculated
>> + * coord: function output parameter holding the i/q coordinate
>> + */
>> +void cordic_calc_iq(s32 theta, struct cordic_iq *coord)
> As "coord" is only for output, why not have this be a function returning a
> struct cordic_iq?
Only to avoid passing the structure over the stack. Given the fact that
it is only 8 bytes (4 bytes extra) I think it is ok to change it.
Gr. AvS
--
Almost nobody dances sober, unless they happen to be insane.
-- H.P. Lovecraft --