(no subject)

(no subject)

[Ben Gamari]

Bcc: 
Subject: GPIO chip select support in omap2_mcspi driver

Hey,

Recently I have been looking to use a BeagleBoard to drive several
serial ADCs and DACs in a data acquisition and analysis setup. Unfortunately, the
BeagleBoard is severely limited by the number of SPI controllers it
exposes on the expansion connector (McSPI3 with 2 CS lines and McSPI4
with one). This is insufficient for our application and thus I have been
investigating adding support to the mcspi driver for using GPIO lines as
chip select lines, as is done in the pxa2xx, bfin5xx, and s3c24xx drivers.

To this end, I have a few questions about how this support was
implemented. First, it seems that the s3c24xx driver is built on the
spi_bitbang driver, despite interfacing with a dedicated hardware SPI
controller.  What is the reason for this? Was this done specifically for
the purpose of incorporating support for GPIO CS pins?

It seems like the rough idea is to add a cs_gpio field to the device
struct (omap2_mcspi) and add the appropriate code to the
omap2_mcspi_force_cs() to bring cs_gpio high or low if it is valid. The
potential problem I can see with this is that omap2_mcspi_set_enable()
is called to enable the channel before the force_cs() is called (in
omap2_mcspi_work()). If I'm interpreting the documentation correctly,
the enable bit starts the clocks, meaning that the chip will begin
clocking out data before CS is brought high. I must be missing something
here, no?

For reference, I included a short list of relevant commits below, largely for
my own benefit. I would greatly appreciate any feedback you might have.

Thanks,
- Ben


pxa2xx_spi: a7bb3909b3293d503211d7f6af8ed62c1644b686
bfin_spi: 42c78b2bf51bafb4cfa98dfecc28dd9b8bcd04b0

------------------------------------------------------------------------------
Throughout its 18-year history, RSA Conference consistently attracts the
world's best and brightest in the field, creating opportunities for Conference
attendees to learn about information security's most important issues through
interactions with peers, luminaries and emerging and established companies.
http://p.sf.net/sfu/rsaconf-dev2dev

Re:

[Ben Dooks]

Ben Gamari wrote:
> Bcc: 
> Subject: GPIO chip select support in omap2_mcspi driver
> 
> Hey,
> 
> Recently I have been looking to use a BeagleBoard to drive several
> serial ADCs and DACs in a data acquisition and analysis setup. Unfortunately, the
> BeagleBoard is severely limited by the number of SPI controllers it
> exposes on the expansion connector (McSPI3 with 2 CS lines and McSPI4
> with one). This is insufficient for our application and thus I have been
> investigating adding support to the mcspi driver for using GPIO lines as
> chip select lines, as is done in the pxa2xx, bfin5xx, and s3c24xx drivers.
> 
> To this end, I have a few questions about how this support was
> implemented. First, it seems that the s3c24xx driver is built on the
> spi_bitbang driver, despite interfacing with a dedicated hardware SPI
> controller.  What is the reason for this? Was this done specifically for
> the purpose of incorporating support for GPIO CS pins?

The spi_bitbang driver also has a really useful spi queue and workqueue
built into it, which is what the s3c24xx spi driver actually bothers to
use.

> It seems like the rough idea is to add a cs_gpio field to the device
> struct (omap2_mcspi) and add the appropriate code to the
> omap2_mcspi_force_cs() to bring cs_gpio high or low if it is valid. The
> potential problem I can see with this is that omap2_mcspi_set_enable()
> is called to enable the channel before the force_cs() is called (in
> omap2_mcspi_work()). If I'm interpreting the documentation correctly,
> the enable bit starts the clocks, meaning that the chip will begin
> clocking out data before CS is brought high. I must be missing something
> here, no?
> 
> For reference, I included a short list of relevant commits below, largely for
> my own benefit. I would greatly appreciate any feedback you might have.
> 
> Thanks,
> - Ben
> 
> 
> pxa2xx_spi: a7bb3909b3293d503211d7f6af8ed62c1644b686
> bfin_spi: 42c78b2bf51bafb4cfa98dfecc28dd9b8bcd04b0

Re: (no subject)

[Ben Dooks]

Ben Gamari wrote:
> Bcc: 
> Subject: GPIO chip select support in omap2_mcspi driver
> 
> Hey,
> 
> Recently I have been looking to use a BeagleBoard to drive several
> serial ADCs and DACs in a data acquisition and analysis setup. Unfortunately, the
> BeagleBoard is severely limited by the number of SPI controllers it
> exposes on the expansion connector (McSPI3 with 2 CS lines and McSPI4
> with one). This is insufficient for our application and thus I have been
> investigating adding support to the mcspi driver for using GPIO lines as
> chip select lines, as is done in the pxa2xx, bfin5xx, and s3c24xx drivers.
> 
> To this end, I have a few questions about how this support was
> implemented. First, it seems that the s3c24xx driver is built on the
> spi_bitbang driver, despite interfacing with a dedicated hardware SPI
> controller.  What is the reason for this? Was this done specifically for
> the purpose of incorporating support for GPIO CS pins?

The spi_bitbang driver also has a really useful spi queue and workqueue
built into it, which is what the s3c24xx spi driver actually bothers to
use.

> It seems like the rough idea is to add a cs_gpio field to the device
> struct (omap2_mcspi) and add the appropriate code to the
> omap2_mcspi_force_cs() to bring cs_gpio high or low if it is valid. The
> potential problem I can see with this is that omap2_mcspi_set_enable()
> is called to enable the channel before the force_cs() is called (in
> omap2_mcspi_work()). If I'm interpreting the documentation correctly,
> the enable bit starts the clocks, meaning that the chip will begin
> clocking out data before CS is brought high. I must be missing something
> here, no?
> 
> For reference, I included a short list of relevant commits below, largely for
> my own benefit. I would greatly appreciate any feedback you might have.
> 
> Thanks,
> - Ben
> 
> 
> pxa2xx_spi: a7bb3909b3293d503211d7f6af8ed62c1644b686
> bfin_spi: 42c78b2bf51bafb4cfa98dfecc28dd9b8bcd04b0


------------------------------------------------------------------------------
Throughout its 18-year history, RSA Conference consistently attracts the
world's best and brightest in the field, creating opportunities for Conference
attendees to learn about information security's most important issues through
interactions with peers, luminaries and emerging and established companies.
http://p.sf.net/sfu/rsaconf-dev2dev

Re:

[Ben Dooks]

[-- Attachment #1: Type: text/plain, Size: 1981 bytes --]

Ben Gamari wrote:
> Bcc: 
> Subject: GPIO chip select support in omap2_mcspi driver
> 
> Hey,
> 
> Recently I have been looking to use a BeagleBoard to drive several
> serial ADCs and DACs in a data acquisition and analysis setup. Unfortunately, the
> BeagleBoard is severely limited by the number of SPI controllers it
> exposes on the expansion connector (McSPI3 with 2 CS lines and McSPI4
> with one). This is insufficient for our application and thus I have been
> investigating adding support to the mcspi driver for using GPIO lines as
> chip select lines, as is done in the pxa2xx, bfin5xx, and s3c24xx drivers.
> 
> To this end, I have a few questions about how this support was
> implemented. First, it seems that the s3c24xx driver is built on the
> spi_bitbang driver, despite interfacing with a dedicated hardware SPI
> controller.  What is the reason for this? Was this done specifically for
> the purpose of incorporating support for GPIO CS pins?

The spi_bitbang driver also has a really useful spi queue and workqueue
built into it, which is what the s3c24xx spi driver actually bothers to
use.

> It seems like the rough idea is to add a cs_gpio field to the device
> struct (omap2_mcspi) and add the appropriate code to the
> omap2_mcspi_force_cs() to bring cs_gpio high or low if it is valid. The
> potential problem I can see with this is that omap2_mcspi_set_enable()
> is called to enable the channel before the force_cs() is called (in
> omap2_mcspi_work()). If I'm interpreting the documentation correctly,
> the enable bit starts the clocks, meaning that the chip will begin
> clocking out data before CS is brought high. I must be missing something
> here, no?
> 
> For reference, I included a short list of relevant commits below, largely for
> my own benefit. I would greatly appreciate any feedback you might have.
> 
> Thanks,
> - Ben
> 
> 
> pxa2xx_spi: a7bb3909b3293d503211d7f6af8ed62c1644b686
> bfin_spi: 42c78b2bf51bafb4cfa98dfecc28dd9b8bcd04b0


[-- Attachment #2: Type: text/plain, Size: 409 bytes --]

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Re:

[Ben Gamari]

Excerpts from Ben Gamari's message of Wed Jan 20 14:47:23 -0500 2010:
> Bcc: 
> Subject: GPIO chip select support in omap2_mcspi driver
> 
> It seems like the rough idea is to add a cs_gpio field to the device
> struct (omap2_mcspi) and add the appropriate code to the
> omap2_mcspi_force_cs() to bring cs_gpio high or low if it is valid. The
> potential problem I can see with this is that omap2_mcspi_set_enable()
> is called to enable the channel before the force_cs() is called (in
> omap2_mcspi_work()). If I'm interpreting the documentation correctly,
> the enable bit starts the clocks, meaning that the chip will begin
> clocking out data before CS is brought high. I must be missing something
> here, no?

Could someone comment on how this ordering works? As I said, it seems to
me like the SPI controller starts sending before CS is brought high.
I would appreciate any feedback. Thanks!

- Ben

McSPI questions pertaining to GPIO chip select support

[Ben Gamari]

Hey all!

Recently I've been thinking about adding support to the McSPI driver for
using GPIO pins as chip selects. As a starting point, I've browsed the
driver source trying to identify what changes would be necessary to add
this support. It seems like the rough idea is,

  a) add a cs_gpio field to the device struct (omap2_mcspi)
  b) modify omap2_mcspi_force_cs() to use cs_gpio instead of the
     CHxCONF[FORCE] bit if cs_gpio is valid

Unfortunately, I'm having a bit of difficulty seeing how the existing
configuration works. In master mode, it seems that the controller is
configured in single forced channel mode (MCSPI_MODULECTRL_SINGLE).  As
far as I can tell, this means that the driver is responsible for
managing the chip selects through the MCSPI_CHxCONF[FORCE] bits. It
seems that this is ideal as little will need to be changed to
incorporate GPIO CS support.

Nevertheless, the timing of the various operations isn't making sense to
me. As far as I understand it, the callgraph is as follows,


omap2_mcspi_work():
  loop over messages
    omap2_mcspi_set_enable(1)
    loop over transfers:
      configure bus parameters
      if (!cs_active) cs = 1
      if (dma):
        omap2_mcspi_txrx_dma()
      else:
        omap2_mcspi_txrx_pio()
      if (cs_change) cs = 0
    end loop
  
    if (cs_active) cs = 0
    omap2_mcspi_set_enable(0)
  end loop


It seems that omap2_mcspi_set_enable() is called to enable the channel
(MCSPI_CHCTRLx[EN] is set) before force_cs() is called. If I'm
interpreting the hardware documentation correctly, the enable bit (among
other things) starts the SPI clock, meaning that the chip will begin
clocking out zeros to the device before CS is brought high.
Furthermore, even after CS is brought high, it seems there could be a
fair amount of time before the chip begins actually clocking out valid
data.

As I am writing this, it now occurs to me that perhaps the chip doesn't
start SPI_CLK until it has data to send. It seems that if this were the
case my concerns would be resolved. However, it is not at all clear that
this is the case from the documentation. When exactly does the
controller start the bus clock? Is this stated explicitly anywhere in
the documentation?

Any input you could offer would be greatly appreciated.
Thanks for your time.

- Ben


P.S. The more and more I think about it, it seems like my hypothesis is
the only logical behavior. It would be great if someone could confirm my
suspicions, however. It really seems like this should be in the
documentation either way.

P.P.S. I apologize if this is something someone familiar with SPI should
just know. My knowledge is a little spotty on this sort of thing.

Re: McSPI questions pertaining to GPIO chip select support

[Bill Gatliff]

Ben Gamari wrote:
> As I am writing this, it now occurs to me that perhaps the chip doesn't
> start SPI_CLK until it has data to send.

... or receive.  This is indeed the case.


b.g.

-- 
Bill Gatliff
Embedded systems training and consulting
http://billgatliff.com
bgat@billgatliff.com

Re: McSPI questions pertaining to GPIO chip select support

[Ben Gamari]

Excerpts from Bill Gatliff's message of Wed Jan 27 23:15:05 -0500 2010:
> Ben Gamari wrote:
> > As I am writing this, it now occurs to me that perhaps the chip doesn't
> > start SPI_CLK until it has data to send.
> 
> ... or receive.  This is indeed the case.
> 
Thanks for your prompt reply. Hopefully you'll see a patch from me about
this in the next few days. I'm assuming this functionality would be
welcome in mainline?

- Ben

Re: McSPI questions pertaining to GPIO chip select support

[Bill Gatliff]

Ben Gamari wrote:
> Thanks for your prompt reply. Hopefully you'll see a patch from me about
> this in the next few days. I'm assuming this functionality would be
> welcome in mainline?
>   

Heck if I know.  :)

But seriously, seems like SPI slave-selects are always in short supply. 
So yeah, people will find your patches very useful.


b.g.

-- 
Bill Gatliff
Embedded systems training and consulting
http://billgatliff.com
bgat@billgatliff.com

Re: McSPI questions pertaining to GPIO chip select support

[jassi brar]

On Thu, Jan 28, 2010 at 1:10 PM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Hey all!
>
> Recently I've been thinking about adding support to the McSPI driver for
> using GPIO pins as chip selects. As a starting point, I've browsed the
> driver source trying to identify what changes would be necessary to add
> this support. It seems like the rough idea is,
You may loot at drivers/spi/spi_s3c64xx.c in Grant Likely's tree.

It doesn't put limit on the number of CS and not even on whether
the CS mechanism is simple GPIO toggling(though the callback
type is defined to match gpio_set_value).
For platform side of it, you need to look in to Ben Dooks' tree.

hth

------------------------------------------------------------------------------
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[RFC PATCH] GPIO chip select support for McSPI

[Ben Gamari]

As you may recall, about a year ago I wrote wondering whether it was possible
to use GPIO lines as chip selects in the McSPI driver. A few of you pointed out
that this functionality had been added to other drivers and it should be quite
simple to do the same for McSPI. Two semesters then passed without a followup
from me.

Thankfully, classes are over and I've had some downtime due to sickness,
finally freeing up some time to look at this (just in time as we'll soon need
this functionality). This morning I looked through the relevant code and put
together this patch to add support for GPIO CSs. As was suggested, I modelled
this after the approach taken in the s3c24xx-spi driver. Let me know whether
this looks sane. It has yet to see hardware, but in principle things look
alright (famous last words).

Cheers,

- Ben


P.S. In case people are curious to see an example of usage I have a patch
adding support for multiplexed chip selects to support a data acquisition board
for the BeagleBoard that I've been working on[1]. I can send these out if
people are interested.

[1] http://goldnerlab.physics.umass.edu/wiki/BeagleBoardDaq

Re: McSPI questions pertaining to GPIO chip select support

[Ben Gamari]

Excerpts from jassi brar's message of Wed Jan 27 23:33:20 -0500 2010:
> On Thu, Jan 28, 2010 at 1:10 PM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > Hey all!
> >
> > Recently I've been thinking about adding support to the McSPI driver for
> > using GPIO pins as chip selects. As a starting point, I've browsed the
> > driver source trying to identify what changes would be necessary to add
> > this support. It seems like the rough idea is,
> You may loot at drivers/spi/spi_s3c64xx.c in Grant Likely's tree.
> 
Grant,

I think that you might be missing a file in your spi-next branch. I've
been unable to find <plat/s3c64xx-spi.h> as referenced in
drivers/spi/spi_s3c64xx.c. I don't have an ARM toolchain to try
compiling the tree at the moment, but both ctags and find have been
unable to find this header. Sorry if I'm just being dense.

Cheers,

- Ben

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Personal 24x7 support from experience hosting pros just a phone call away.
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Re: McSPI questions pertaining to GPIO chip select support

[jassi brar]

On Fri, Jan 29, 2010 at 9:32 AM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Excerpts from jassi brar's message of Wed Jan 27 23:33:20 -0500 2010:
>> On Thu, Jan 28, 2010 at 1:10 PM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> > Hey all!
>> >
>> > Recently I've been thinking about adding support to the McSPI driver for
>> > using GPIO pins as chip selects. As a starting point, I've browsed the
>> > driver source trying to identify what changes would be necessary to add
>> > this support. It seems like the rough idea is,
>> You may loot at drivers/spi/spi_s3c64xx.c in Grant Likely's tree.
>>
> Grant,
>
> I think that you might be missing a file in your spi-next branch. I've
> been unable to find <plat/s3c64xx-spi.h> as referenced in
> drivers/spi/spi_s3c64xx.c. I don't have an ARM toolchain to try
> compiling the tree at the moment, but both ctags and find have been
> unable to find this header. Sorry if I'm just being dense.
the arch/mach specific stuff will come via the SoC maintainer's(Ben
Dooks) tree as I already mentioned.

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Re: McSPI questions pertaining to GPIO chip select support

[Ben Gamari]

Excerpts from jassi brar's message of Thu Jan 28 20:09:47 -0500 2010:
> the arch/mach specific stuff will come via the SoC maintainer's(Ben
> Dooks) tree as I already mentioned.

Crap. Sorry for the noise. Looks like I just need to learn to read.

- Ben

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[RFC PATCH] GPIO chip select support for McSPI

[Ben Gamari]

As you may recall, about a year ago I wrote wondering whether it was possible
to use GPIO lines as chip selects in the McSPI driver. A few of you pointed out
that this functionality had been added to other drivers and it should be quite
simple to do the same for McSPI. Two semesters then passed without a followup
from me.

Thankfully, classes are over and I've had some downtime due to sickness,
finally freeing up some time to look at this (just in time as we'll soon need
this functionality). This morning I looked through the relevant code and put
together this patch to add support for GPIO CSs. As was suggested, I modelled
this after the approach taken in the s3c24xx-spi driver. Let me know whether
this looks sane. It has yet to see hardware, but in principle things look
alright (famous last words).

Cheers,

- Ben


P.S. In case people are curious to see an example of usage I have a patch
adding support for multiplexed chip selects to support a data acquisition board
for the BeagleBoard that I've been working on[1]. I can send these out if
people are interested.

[1] http://goldnerlab.physics.umass.edu/wiki/BeagleBoardDaq


------------------------------------------------------------------------------
Forrester recently released a report on the Return on Investment (ROI) of
Google Apps. They found a 300% ROI, 38%-56% cost savings, and break-even
within 7 months.  Over 3 million businesses have gone Google with Google Apps:
an online email calendar, and document program that's accessible from your 
browser. Read the Forrester report: http://p.sf.net/sfu/googleapps-sfnew

[PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

This mechanism is in large part stolen from the s3c64xx-spi module. To
use this functionality, one simply must define a set_level function to
set the CS state and a omap2_mcspi_csinfo struct for each chip select in
the board file.

Each spi_board_info.controller_data should then be set
to point to the appropriate csinfo struct. This will cause the driver to
call the csinfo->set_level function instead of toggling the McSPI chip
select lines.

Signed-off-by: Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 arch/arm/plat-omap/include/plat/mcspi.h |   14 ++++++++++++++
 drivers/spi/omap2_mcspi.c               |   14 +++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
index 1254e49..ab84b8d 100644
--- a/arch/arm/plat-omap/include/plat/mcspi.h
+++ b/arch/arm/plat-omap/include/plat/mcspi.h
@@ -1,6 +1,20 @@
 #ifndef _OMAP2_MCSPI_H
 #define _OMAP2_MCSPI_H
 
+/**
+ * struct omap2_mcspi_csinfo - Chip Select description
+ * @line: Custom 'identity' of the CS line
+ * @set_level: Function to set the state of a given CS line
+ *
+ * This is to allow use of GPIO lines as CS lines. Allocate and initialize one
+ * in the machine init code and make spi_board_info.controller_data point to
+ * it.
+ */
+struct omap2_mcspi_csinfo {
+        unsigned line;
+        void (*set_level)(unsigned line_id, int lvl);
+};
+
 struct omap2_mcspi_platform_config {
 	unsigned short	num_cs;
 };
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 2a651e6..92ccbd6 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 
 #include <linux/spi/spi.h>
+#include <linux/gpio.h>
 
 #include <plat/dma.h>
 #include <plat/clock.h>
@@ -235,11 +236,14 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
 
 static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
 {
-	u32 l;
-
-	l = mcspi_cached_chconf0(spi);
-	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
-	mcspi_write_chconf0(spi, l);
+	if (spi->controller_data) {
+		struct omap2_mcspi_csinfo *csinfo = spi->controller_data;
+		(*csinfo->set_level)(csinfo->line, cs_active);
+	} else {
+		u32 l = mcspi_cached_chconf0(spi);
+		MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
+		mcspi_write_chconf0(spi, l);
+	}
 }
 
 static void omap2_mcspi_set_master_mode(struct spi_master *master)
-- 
1.7.1


------------------------------------------------------------------------------
Forrester recently released a report on the Return on Investment (ROI) of
Google Apps. They found a 300% ROI, 38%-56% cost savings, and break-even
within 7 months.  Over 3 million businesses have gone Google with Google Apps:
an online email calendar, and document program that's accessible from your 
browser. Read the Forrester report: http://p.sf.net/sfu/googleapps-sfnew

[PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

This mechanism is in large part stolen from the s3c64xx-spi module. To
use this functionality, one simply must define a set_level function to
set the CS state and a omap2_mcspi_csinfo struct for each chip select in
the board file.

Each spi_board_info.controller_data should then be set
to point to the appropriate csinfo struct. This will cause the driver to
call the csinfo->set_level function instead of toggling the McSPI chip
select lines.

Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
---
 arch/arm/plat-omap/include/plat/mcspi.h |   14 ++++++++++++++
 drivers/spi/omap2_mcspi.c               |   14 +++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
index 1254e49..ab84b8d 100644
--- a/arch/arm/plat-omap/include/plat/mcspi.h
+++ b/arch/arm/plat-omap/include/plat/mcspi.h
@@ -1,6 +1,20 @@
 #ifndef _OMAP2_MCSPI_H
 #define _OMAP2_MCSPI_H
 
+/**
+ * struct omap2_mcspi_csinfo - Chip Select description
+ * @line: Custom 'identity' of the CS line
+ * @set_level: Function to set the state of a given CS line
+ *
+ * This is to allow use of GPIO lines as CS lines. Allocate and initialize one
+ * in the machine init code and make spi_board_info.controller_data point to
+ * it.
+ */
+struct omap2_mcspi_csinfo {
+        unsigned line;
+        void (*set_level)(unsigned line_id, int lvl);
+};
+
 struct omap2_mcspi_platform_config {
 	unsigned short	num_cs;
 };
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 2a651e6..92ccbd6 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 
 #include <linux/spi/spi.h>
+#include <linux/gpio.h>
 
 #include <plat/dma.h>
 #include <plat/clock.h>
@@ -235,11 +236,14 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
 
 static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
 {
-	u32 l;
-
-	l = mcspi_cached_chconf0(spi);
-	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
-	mcspi_write_chconf0(spi, l);
+	if (spi->controller_data) {
+		struct omap2_mcspi_csinfo *csinfo = spi->controller_data;
+		(*csinfo->set_level)(csinfo->line, cs_active);
+	} else {
+		u32 l = mcspi_cached_chconf0(spi);
+		MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
+		mcspi_write_chconf0(spi, l);
+	}
 }
 
 static void omap2_mcspi_set_master_mode(struct spi_master *master)
-- 
1.7.1

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Tony Lindgren]

* Ben Gamari <bgamari.foss@gmail.com> [101221 09:56]:
> This mechanism is in large part stolen from the s3c64xx-spi module. To
> use this functionality, one simply must define a set_level function to
> set the CS state and a omap2_mcspi_csinfo struct for each chip select in
> the board file.
> 
> Each spi_board_info.controller_data should then be set
> to point to the appropriate csinfo struct. This will cause the driver to
> call the csinfo->set_level function instead of toggling the McSPI chip
> select lines.
> 
> Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>

This one should go via the SPI list:

Acked-by: Tony Lindgren <tony@atomide.com>

> ---
>  arch/arm/plat-omap/include/plat/mcspi.h |   14 ++++++++++++++
>  drivers/spi/omap2_mcspi.c               |   14 +++++++++-----
>  2 files changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
> index 1254e49..ab84b8d 100644
> --- a/arch/arm/plat-omap/include/plat/mcspi.h
> +++ b/arch/arm/plat-omap/include/plat/mcspi.h
> @@ -1,6 +1,20 @@
>  #ifndef _OMAP2_MCSPI_H
>  #define _OMAP2_MCSPI_H
>  
> +/**
> + * struct omap2_mcspi_csinfo - Chip Select description
> + * @line: Custom 'identity' of the CS line
> + * @set_level: Function to set the state of a given CS line
> + *
> + * This is to allow use of GPIO lines as CS lines. Allocate and initialize one
> + * in the machine init code and make spi_board_info.controller_data point to
> + * it.
> + */
> +struct omap2_mcspi_csinfo {
> +        unsigned line;
> +        void (*set_level)(unsigned line_id, int lvl);
> +};
> +
>  struct omap2_mcspi_platform_config {
>  	unsigned short	num_cs;
>  };
> diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
> index 2a651e6..92ccbd6 100644
> --- a/drivers/spi/omap2_mcspi.c
> +++ b/drivers/spi/omap2_mcspi.c
> @@ -35,6 +35,7 @@
>  #include <linux/slab.h>
>  
>  #include <linux/spi/spi.h>
> +#include <linux/gpio.h>
>  
>  #include <plat/dma.h>
>  #include <plat/clock.h>
> @@ -235,11 +236,14 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
>  
>  static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
>  {
> -	u32 l;
> -
> -	l = mcspi_cached_chconf0(spi);
> -	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> -	mcspi_write_chconf0(spi, l);
> +	if (spi->controller_data) {
> +		struct omap2_mcspi_csinfo *csinfo = spi->controller_data;
> +		(*csinfo->set_level)(csinfo->line, cs_active);
> +	} else {
> +		u32 l = mcspi_cached_chconf0(spi);
> +		MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> +		mcspi_write_chconf0(spi, l);
> +	}
>  }
>  
>  static void omap2_mcspi_set_master_mode(struct spi_master *master)
> -- 
> 1.7.1
> 
> --
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Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Tue, Dec 21, 2010 at 10:56 AM, Ben Gamari <bgamari.foss@gmail.com> wrote:
> This mechanism is in large part stolen from the s3c64xx-spi module. To
> use this functionality, one simply must define a set_level function to
> set the CS state and a omap2_mcspi_csinfo struct for each chip select in
> the board file.
>
> Each spi_board_info.controller_data should then be set
> to point to the appropriate csinfo struct. This will cause the driver to
> call the csinfo->set_level function instead of toggling the McSPI chip
> select lines.
>
> Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>

I'd rather see the spi driver modified to use the gpio api directly.
The drivers are already tending in that direction and it doesn't
require machine specific set_level functions to be defined.

g.

> ---
>  arch/arm/plat-omap/include/plat/mcspi.h |   14 ++++++++++++++
>  drivers/spi/omap2_mcspi.c               |   14 +++++++++-----
>  2 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
> index 1254e49..ab84b8d 100644
> --- a/arch/arm/plat-omap/include/plat/mcspi.h
> +++ b/arch/arm/plat-omap/include/plat/mcspi.h
> @@ -1,6 +1,20 @@
>  #ifndef _OMAP2_MCSPI_H
>  #define _OMAP2_MCSPI_H
>
> +/**
> + * struct omap2_mcspi_csinfo - Chip Select description
> + * @line: Custom 'identity' of the CS line
> + * @set_level: Function to set the state of a given CS line
> + *
> + * This is to allow use of GPIO lines as CS lines. Allocate and initialize one
> + * in the machine init code and make spi_board_info.controller_data point to
> + * it.
> + */
> +struct omap2_mcspi_csinfo {
> +        unsigned line;
> +        void (*set_level)(unsigned line_id, int lvl);
> +};
> +
>  struct omap2_mcspi_platform_config {
>        unsigned short  num_cs;
>  };
> diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
> index 2a651e6..92ccbd6 100644
> --- a/drivers/spi/omap2_mcspi.c
> +++ b/drivers/spi/omap2_mcspi.c
> @@ -35,6 +35,7 @@
>  #include <linux/slab.h>
>
>  #include <linux/spi/spi.h>
> +#include <linux/gpio.h>
>
>  #include <plat/dma.h>
>  #include <plat/clock.h>
> @@ -235,11 +236,14 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
>
>  static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
>  {
> -       u32 l;
> -
> -       l = mcspi_cached_chconf0(spi);
> -       MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> -       mcspi_write_chconf0(spi, l);
> +       if (spi->controller_data) {
> +               struct omap2_mcspi_csinfo *csinfo = spi->controller_data;
> +               (*csinfo->set_level)(csinfo->line, cs_active);
> +       } else {
> +               u32 l = mcspi_cached_chconf0(spi);
> +               MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> +               mcspi_write_chconf0(spi, l);
> +       }
>  }
>
>  static void omap2_mcspi_set_master_mode(struct spi_master *master)
> --
> 1.7.1
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

On Thu, 23 Dec 2010 14:38:57 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Tue, Dec 21, 2010 at 10:56 AM, Ben Gamari <bgamari.foss@gmail.com> wrote:
> > This mechanism is in large part stolen from the s3c64xx-spi module. To
> > use this functionality, one simply must define a set_level function to
> > set the CS state and a omap2_mcspi_csinfo struct for each chip select in
> > the board file.
> >
> > Each spi_board_info.controller_data should then be set
> > to point to the appropriate csinfo struct. This will cause the driver to
> > call the csinfo->set_level function instead of toggling the McSPI chip
> > select lines.
> >
> > Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
> 
> I'd rather see the spi driver modified to use the gpio api directly.
> The drivers are already tending in that direction and it doesn't
> require machine specific set_level functions to be defined.
> 
The reason I left this up to the board is it's easy to foresee cases
where you want a non-trivial mapping between logical CS numbers and CS
pin states. In my case, I using a 2-to-4 multiplexer as the source of
chip select.

- Ben

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Thu, Dec 23, 2010 at 4:09 PM, Ben Gamari <bgamari.foss@gmail.com> wrote:
> On Thu, 23 Dec 2010 14:38:57 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
>> On Tue, Dec 21, 2010 at 10:56 AM, Ben Gamari <bgamari.foss@gmail.com> wrote:
>> > This mechanism is in large part stolen from the s3c64xx-spi module. To
>> > use this functionality, one simply must define a set_level function to
>> > set the CS state and a omap2_mcspi_csinfo struct for each chip select in
>> > the board file.
>> >
>> > Each spi_board_info.controller_data should then be set
>> > to point to the appropriate csinfo struct. This will cause the driver to
>> > call the csinfo->set_level function instead of toggling the McSPI chip
>> > select lines.
>> >
>> > Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
>>
>> I'd rather see the spi driver modified to use the gpio api directly.
>> The drivers are already tending in that direction and it doesn't
>> require machine specific set_level functions to be defined.
>>
> The reason I left this up to the board is it's easy to foresee cases
> where you want a non-trivial mapping between logical CS numbers and CS
> pin states. In my case, I using a 2-to-4 multiplexer as the source of
> chip select.

Hi Ben,

I understand and appreciate the motivation.  However in practice, the
gpio api is sufficient for pretty much any use case, even when the
backing gpio controller driver ends up driving some oddball device
with different constraints.  The big downside to using a callback is
that it forces all users to do the extra work of implementing the
callback.  With the gpio api, only the oddball cases have to do extra
code (to adapt the custom device to the gpio api).

g.

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

On Thu, 23 Dec 2010 17:37:12 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Thu, Dec 23, 2010 at 4:09 PM, Ben Gamari <bgamari.foss@gmail.com> wrote:
> > The reason I left this up to the board is it's easy to foresee cases
> > where you want a non-trivial mapping between logical CS numbers and CS
> > pin states. In my case, I using a 2-to-4 multiplexer as the source of
> > chip select.
> 
> Hi Ben,
> 
> I understand and appreciate the motivation.  However in practice, the
> gpio api is sufficient for pretty much any use case, even when the
> backing gpio controller driver ends up driving some oddball device
> with different constraints.  The big downside to using a callback is
> that it forces all users to do the extra work of implementing the
> callback.  With the gpio api, only the oddball cases have to do extra
> code (to adapt the custom device to the gpio api).

I understand your concerns, but I'm not sure how to satisfy them without
crippling the design's ability to accomodate my use-case. I can't pass a
GPIO line per spi_board_info since in my case of a multiplexed CS
configuration a single pin's state does not uniquely determine the
desired CS. The only other option I can think of is that we somehow
provide a list of GPIOs for each bus and map the CS numbers to
permutations of GPIO states. Unfortunately, I don't know of any suitable
structure to put this GPIO list in. Perhaps I'm missing something obvious?

- Ben

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Thu, Dec 23, 2010 at 09:27:20PM -0500, Ben Gamari wrote:
> On Thu, 23 Dec 2010 17:37:12 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> > On Thu, Dec 23, 2010 at 4:09 PM, Ben Gamari <bgamari.foss@gmail.com> wrote:
> > > The reason I left this up to the board is it's easy to foresee cases
> > > where you want a non-trivial mapping between logical CS numbers and CS
> > > pin states. In my case, I using a 2-to-4 multiplexer as the source of
> > > chip select.
> > 
> > Hi Ben,
> > 
> > I understand and appreciate the motivation.  However in practice, the
> > gpio api is sufficient for pretty much any use case, even when the
> > backing gpio controller driver ends up driving some oddball device
> > with different constraints.  The big downside to using a callback is
> > that it forces all users to do the extra work of implementing the
> > callback.  With the gpio api, only the oddball cases have to do extra
> > code (to adapt the custom device to the gpio api).
> 
> I understand your concerns, but I'm not sure how to satisfy them without
> crippling the design's ability to accomodate my use-case. I can't pass a
> GPIO line per spi_board_info since in my case of a multiplexed CS
> configuration a single pin's state does not uniquely determine the
> desired CS. The only other option I can think of is that we somehow
> provide a list of GPIOs for each bus and map the CS numbers to
> permutations of GPIO states. Unfortunately, I don't know of any suitable
> structure to put this GPIO list in. Perhaps I'm missing something obvious?

Close, but not quite.  Assign one gpio number to each cs state, and
write a gpio controller driver that maps the linux-gpio number to the
physical gpio state permutation.  The mapping from gpio# to ss# is
1:1, but the driver behind the gpio# can do whatever you need it to
do.

g.

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

On Thu, 23 Dec 2010 20:28:19 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Thu, Dec 23, 2010 at 09:27:20PM -0500, Ben Gamari wrote:
> > I understand your concerns, but I'm not sure how to satisfy them without
> > crippling the design's ability to accomodate my use-case. I can't pass a
> > GPIO line per spi_board_info since in my case of a multiplexed CS
> > configuration a single pin's state does not uniquely determine the
> > desired CS. The only other option I can think of is that we somehow
> > provide a list of GPIOs for each bus and map the CS numbers to
> > permutations of GPIO states. Unfortunately, I don't know of any suitable
> > structure to put this GPIO list in. Perhaps I'm missing something obvious?
> 
> Close, but not quite.  Assign one gpio number to each cs state, and
> write a gpio controller driver that maps the linux-gpio number to the
> physical gpio state permutation.  The mapping from gpio# to ss# is
> 1:1, but the driver behind the gpio# can do whatever you need it to
> do.
> 
I see. I'm still not convinced that this is the route to take,
however. It seems like this virtual gpio interface is not only pretty
clunky (simple board file glue turns into an entire gpio chip driver),
it seems like this is a very inaccurate and not very useful way to
expose a multiplexed CS configuration; e.g. what is this chip driver to
do if the user tries to set two CS pins at once? Is there precedent for
using the GPIO subsystem in this way?

Cheers,

- Ben

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Fri, Dec 24, 2010 at 01:05:56AM -0500, Ben Gamari wrote:
> On Thu, 23 Dec 2010 20:28:19 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> > On Thu, Dec 23, 2010 at 09:27:20PM -0500, Ben Gamari wrote:
> > > I understand your concerns, but I'm not sure how to satisfy them without
> > > crippling the design's ability to accomodate my use-case. I can't pass a
> > > GPIO line per spi_board_info since in my case of a multiplexed CS
> > > configuration a single pin's state does not uniquely determine the
> > > desired CS. The only other option I can think of is that we somehow
> > > provide a list of GPIOs for each bus and map the CS numbers to
> > > permutations of GPIO states. Unfortunately, I don't know of any suitable
> > > structure to put this GPIO list in. Perhaps I'm missing something obvious?
> > 
> > Close, but not quite.  Assign one gpio number to each cs state, and
> > write a gpio controller driver that maps the linux-gpio number to the
> > physical gpio state permutation.  The mapping from gpio# to ss# is
> > 1:1, but the driver behind the gpio# can do whatever you need it to
> > do.
> > 
> I see. I'm still not convinced that this is the route to take,
> however. It seems like this virtual gpio interface is not only pretty
> clunky (simple board file glue turns into an entire gpio chip driver),
> it seems like this is a very inaccurate and not very useful way to
> expose a multiplexed CS configuration; e.g. what is this chip driver to
> do if the user tries to set two CS pins at once?

(Sorry for the really laggy reply)

I don't see it being that big a deal.  gpio drivers are pretty
lightweight and it is fine to have domain-specific limitations on how
gpios for a particular "gpio controller" behave.  In your example, if
the hardware doesn't support enabling 2 CS pins at once, then you make
a choice, either setting one when the other is already set simply does
not work; or it could reset the other state.  Either choice would be
fine.  The SPI driver must do the right thing regardless and deselect
the previous CS line before enabling a new one.

The other alternative would be to implement a new SPI chipselect
common infrastructure, but IMO, that would just end up looking like a
duplication of the gpio infrastructure.

Regardless, my point still stands, platform callbacks for what amounts
to gpio manipulations doesn't make a whole lot of sense.

> Is there precedent for
> using the GPIO subsystem in this way?

Yes, in drivers/spi look at mpc52xx_spi.c, davinci_spi.c, ath79_spi.c,
atmel_spi.c, and many more.  Grep for gpio in drivers/spi.

g.

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

On Sat, 12 Feb 2011 01:33:24 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> (Sorry for the really laggy reply)
> 
No worries, I was just starting to think about this again myself.

> I don't see it being that big a deal.  gpio drivers are pretty
> lightweight and it is fine to have domain-specific limitations on how
> gpios for a particular "gpio controller" behave.  In your example, if
> the hardware doesn't support enabling 2 CS pins at once, then you make
> a choice, either setting one when the other is already set simply does
> not work; or it could reset the other state.  Either choice would be
> fine.  The SPI driver must do the right thing regardless and deselect
> the previous CS line before enabling a new one.
> 
Having now finally having had a chance to implement a gpio_chip driver,
I agree. It's quite simple and seems to fill the need pretty well

> The other alternative would be to implement a new SPI chipselect
> common infrastructure, but IMO, that would just end up looking like a
> duplication of the gpio infrastructure.
> 
I think you are probably right. GPIO seems to be a good fit.

Patch coming shortly.  I use spi_board_info.controller_data to pass the
gpio number to the controller which doesn't seem like the best way
forward, but I wasn't sure how else to proceed. Also, since the gpio
numbers are dynamically determined spi_board_info.controller_data must
be filled in at runtime, which is also a bit of a bummer (although not
easily solved as far as I can tell). Let me know what you think.

 - Ben

Re: McSPI questions pertaining to GPIO chip select support

[Raju Sana]

Hi Ben,

Could you please post your patch as I am also working the similar design.
I need to modify the existing McSPI driver to support 3 codec chips.

Thanks.
Venkat Raju.


On Thu, Jan 28, 2010 at 9:40 AM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Hey all!
>
> Recently I've been thinking about adding support to the McSPI driver for
> using GPIO pins as chip selects. As a starting point, I've browsed the
> driver source trying to identify what changes would be necessary to add
> this support. It seems like the rough idea is,
>
>  a) add a cs_gpio field to the device struct (omap2_mcspi)
>  b) modify omap2_mcspi_force_cs() to use cs_gpio instead of the
>     CHxCONF[FORCE] bit if cs_gpio is valid
>
> Unfortunately, I'm having a bit of difficulty seeing how the existing
> configuration works. In master mode, it seems that the controller is
> configured in single forced channel mode (MCSPI_MODULECTRL_SINGLE).  As
> far as I can tell, this means that the driver is responsible for
> managing the chip selects through the MCSPI_CHxCONF[FORCE] bits. It
> seems that this is ideal as little will need to be changed to
> incorporate GPIO CS support.
>
> Nevertheless, the timing of the various operations isn't making sense to
> me. As far as I understand it, the callgraph is as follows,
>
>
> omap2_mcspi_work():
>  loop over messages
>    omap2_mcspi_set_enable(1)
>    loop over transfers:
>      configure bus parameters
>      if (!cs_active) cs = 1
>      if (dma):
>        omap2_mcspi_txrx_dma()
>      else:
>        omap2_mcspi_txrx_pio()
>      if (cs_change) cs = 0
>    end loop
>
>    if (cs_active) cs = 0
>    omap2_mcspi_set_enable(0)
>  end loop
>
>
> It seems that omap2_mcspi_set_enable() is called to enable the channel
> (MCSPI_CHCTRLx[EN] is set) before force_cs() is called. If I'm
> interpreting the hardware documentation correctly, the enable bit (among
> other things) starts the SPI clock, meaning that the chip will begin
> clocking out zeros to the device before CS is brought high.
> Furthermore, even after CS is brought high, it seems there could be a
> fair amount of time before the chip begins actually clocking out valid
> data.
>
> As I am writing this, it now occurs to me that perhaps the chip doesn't
> start SPI_CLK until it has data to send. It seems that if this were the
> case my concerns would be resolved. However, it is not at all clear that
> this is the case from the documentation. When exactly does the
> controller start the bus clock? Is this stated explicitly anywhere in
> the documentation?
>
> Any input you could offer would be greatly appreciated.
> Thanks for your time.
>
> - Ben
>
>
> P.S. The more and more I think about it, it seems like my hypothesis is
> the only logical behavior. It would be great if someone could confirm my
> suspicions, however. It really seems like this should be in the
> documentation either way.
>
> P.P.S. I apologize if this is something someone familiar with SPI should
> just know. My knowledge is a little spotty on this sort of thing.
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GPIO chip select support

[Ben Gamari]

Thanks for the poke. I've been meaning to send this set out again anyways.

This is the patch I am currently using (on top of v3.0). Conceptually it's
quite similar to the first patches I sent out but some implementation details
were slightly reworked to account for the generalization of the McSPI driver to
other silicon.

I would say that the patch is close to mergable save the fact that there is
currently no clean way to set up GPIO CS pins from a board file. I'll send the
horrible hack I currently use shortly. If anyone has any ideas on how this
might be done cleanly please let me know. It's sad that the mere lack of a
configuration interface is the reason this isn't upstream.

Cheers,

- Ben

[PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

Many applications require more chip select lines than the board or
processor allow. Introduce a mechanism to allow use of GPIO pins as
chip select lines with the McSPI controller. To use this
tionality,
one simply provides a table mapping CS line numbers to GPIO numbers

omap2_mcspi_platform_config.cs_gpios.

Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
---
 arch/arm/plat-omap/include/plat/mcspi.h |    1 +
 drivers/spi/omap2_mcspi.c               |   19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
index 3d51b18..c5670f2 100644
--- a/arch/arm/plat-omap/include/plat/mcspi.h
+++ b/arch/arm/plat-omap/include/plat/mcspi.h
@@ -10,6 +10,7 @@
 struct omap2_mcspi_platform_config {
 	unsigned short	num_cs;
 	unsigned int regs_offset;
+	int *cs_gpios;
 };
 
 struct omap2_mcspi_dev_attr {
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index f41c906..20dec5d 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -36,6 +36,7 @@
 #include <linux/pm_runtime.h>
 
 #include <linux/spi/spi.h>
+#include <linux/gpio.h>
 
 #include <plat/dma.h>
 #include <plat/clock.h>
@@ -121,6 +122,7 @@ struct omap2_mcspi {
 	/* SPI1 has 4 channels, while SPI2 has 2 */
 	struct omap2_mcspi_dma	*dma_channels;
 	struct  device		*dev;
+        int                     *cs_gpios;
 };
 
 struct omap2_mcspi_cs {
@@ -227,7 +229,11 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
 static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
 {
 	u32 l;
+	struct omap2_mcspi* mcspi = spi_master_get_devdata(spi->master);
+	if (mcspi->cs_gpios)
+		gpio_set_value(mcspi->cs_gpios[spi->chip_select], cs_active);
 
+	// TXS times out unless we force the CHCONF reg as well
 	l = mcspi_cached_chconf0(spi);
 	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
 	mcspi_write_chconf0(spi, l);
@@ -1088,6 +1094,8 @@ static int __init omap2_mcspi_probe(struct platform_device *pdev)
 	struct omap2_mcspi	*mcspi;
 	struct resource		*r;
 	int			status = 0, i;
+	struct omap2_mcspi_platform_config* pconfig = pdev->dev.platform_data;
+	int                     num_dma;
 
 	master = spi_alloc_master(&pdev->dev, sizeof *mcspi);
 	if (master == NULL) {
@@ -1110,6 +1118,13 @@ static int __init omap2_mcspi_probe(struct platform_device *pdev)
 
 	mcspi = spi_master_get_devdata(master);
 	mcspi->master = master;
+	if (pconfig && pconfig->cs_gpios) {
+		mcspi->cs_gpios = pconfig->cs_gpios;
+		num_dma = 1;
+	} else {
+		mcspi->cs_gpios = NULL;
+		num_dma = master->num_chipselect;
+	}
 
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (r == NULL) {
@@ -1139,14 +1154,14 @@ static int __init omap2_mcspi_probe(struct platform_device *pdev)
 	INIT_LIST_HEAD(&mcspi->msg_queue);
 	INIT_LIST_HEAD(&omap2_mcspi_ctx[master->bus_num - 1].cs);
 
-	mcspi->dma_channels = kcalloc(master->num_chipselect,
+	mcspi->dma_channels = kcalloc(num_dma,
 			sizeof(struct omap2_mcspi_dma),
 			GFP_KERNEL);
 
 	if (mcspi->dma_channels == NULL)
 		goto err2;
 
-	for (i = 0; i < master->num_chipselect; i++) {
+	for (i = 0; i < num_dma; i++) {
 		char dma_ch_name[14];
 		struct resource *dma_res;
 
-- 
1.7.4.1

[PATCH] beagledaq: Hack in cs_gpios

[Ben Gamari]

---
 arch/arm/mach-omap2/board-omap3beagle.c |    4 ++--
 arch/arm/mach-omap2/devices.c           |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-omap2/board-omap3beagle.c b/arch/arm/mach-omap2/board-omap3beagle.c
index 67999da..481c1a9 100644
--- a/arch/arm/mach-omap2/board-omap3beagle.c
+++ b/arch/arm/mach-omap2/board-omap3beagle.c
@@ -661,8 +661,8 @@ static struct spi_board_info beagledaq_mcspi_board_info[] = {
 	},
 };
 
-static int mcspi3_cs_gpios[4];
-static int mcspi4_cs_gpios[4];
+int mcspi3_cs_gpios[4];
+int mcspi4_cs_gpios[4];
 
 static void __init beagledaq_init(void)
 {
diff --git a/arch/arm/mach-omap2/devices.c b/arch/arm/mach-omap2/devices.c
index 5b8ca68..6808251 100644
--- a/arch/arm/mach-omap2/devices.c
+++ b/arch/arm/mach-omap2/devices.c
@@ -341,6 +341,9 @@ struct omap_device_pm_latency omap_mcspi_latency[] = {
 	},
 };
 
+extern int mcspi3_cs_gpios[4];
+extern int mcspi4_cs_gpios[4];
+
 static int omap_mcspi_init(struct omap_hwmod *oh, void *unused)
 {
 	struct omap_device *od;
@@ -369,6 +372,18 @@ static int omap_mcspi_init(struct omap_hwmod *oh, void *unused)
 			return -EINVAL;
 	}
 
+	/* HACK: Not enough time to figure out how to export cs_gpios from
+	 * board file to driver correctly */
+	if (spi_num == 2) {
+		// Setup McSPI3 cs_gpios
+		pdata->num_cs = 4;
+		pdata->cs_gpios = mcspi3_cs_gpios;
+	} else if (spi_num == 3) {
+		// Setup McSPI4 cs_gpios
+		pdata->num_cs = 4;
+		pdata->cs_gpios = mcspi4_cs_gpios;
+	}
+
 	spi_num++;
 	od = omap_device_build(name, spi_num, oh, pdata,
 				sizeof(*pdata),	omap_mcspi_latency,
-- 
1.7.4.1

Re: [PATCH] beagledaq: Hack in cs_gpios

[Raju Sana]

Hi Ben,

The McSPI1 has got  "num_cs"  as 4.
I would like to use McSPI1 to select my 3 chips based on the two GPIO pins.

Could you please give me some pointers on this.

Thanks,
Venkat Raju.





On Tue, Aug 30, 2011 at 7:22 PM, Ben Gamari <bgamari.foss-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> ---
>  arch/arm/mach-omap2/board-omap3beagle.c |    4 ++--
>  arch/arm/mach-omap2/devices.c           |   15 +++++++++++++++
>  2 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/board-omap3beagle.c
> b/arch/arm/mach-omap2/board-omap3beagle.c
> index 67999da..481c1a9 100644
> --- a/arch/arm/mach-omap2/board-omap3beagle.c
> +++ b/arch/arm/mach-omap2/board-omap3beagle.c
> @@ -661,8 +661,8 @@ static struct spi_board_info
> beagledaq_mcspi_board_info[] = {
>        },
>  };
>
> -static int mcspi3_cs_gpios[4];
> -static int mcspi4_cs_gpios[4];
> +int mcspi3_cs_gpios[4];
> +int mcspi4_cs_gpios[4];
>
>  static void __init beagledaq_init(void)
>  {
> diff --git a/arch/arm/mach-omap2/devices.c b/arch/arm/mach-omap2/devices.c
> index 5b8ca68..6808251 100644
> --- a/arch/arm/mach-omap2/devices.c
> +++ b/arch/arm/mach-omap2/devices.c
> @@ -341,6 +341,9 @@ struct omap_device_pm_latency omap_mcspi_latency[] = {
>        },
>  };
>
> +extern int mcspi3_cs_gpios[4];
> +extern int mcspi4_cs_gpios[4];
> +
>  static int omap_mcspi_init(struct omap_hwmod *oh, void *unused)
>  {
>        struct omap_device *od;
> @@ -369,6 +372,18 @@ static int omap_mcspi_init(struct omap_hwmod *oh, void
> *unused)
>                        return -EINVAL;
>        }
>
> +       /* HACK: Not enough time to figure out how to export cs_gpios from
> +        * board file to driver correctly */
> +       if (spi_num == 2) {
> +               // Setup McSPI3 cs_gpios
> +               pdata->num_cs = 4;
> +               pdata->cs_gpios = mcspi3_cs_gpios;
> +       } else if (spi_num == 3) {
> +               // Setup McSPI4 cs_gpios
> +               pdata->num_cs = 4;
> +               pdata->cs_gpios = mcspi4_cs_gpios;
> +       }
> +
>        spi_num++;
>        od = omap_device_build(name, spi_num, oh, pdata,
>                                sizeof(*pdata), omap_mcspi_latency,
> --
> 1.7.4.1
>
>
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McSPI questions pertaining to GPIO chip select support

[Ben Gamari]

Hey all!

Recently I've been thinking about adding support to the McSPI driver for
using GPIO pins as chip selects. As a starting point, I've browsed the
driver source trying to identify what changes would be necessary to add
this support. It seems like the rough idea is,

  a) add a cs_gpio field to the device struct (omap2_mcspi)
  b) modify omap2_mcspi_force_cs() to use cs_gpio instead of the
     CHxCONF[FORCE] bit if cs_gpio is valid

Unfortunately, I'm having a bit of difficulty seeing how the existing
configuration works. In master mode, it seems that the controller is
configured in single forced channel mode (MCSPI_MODULECTRL_SINGLE).  As
far as I can tell, this means that the driver is responsible for
managing the chip selects through the MCSPI_CHxCONF[FORCE] bits. It
seems that this is ideal as little will need to be changed to
incorporate GPIO CS support.

Nevertheless, the timing of the various operations isn't making sense to
me. As far as I understand it, the callgraph is as follows,


omap2_mcspi_work():
  loop over messages
    omap2_mcspi_set_enable(1)
    loop over transfers:
      configure bus parameters
      if (!cs_active) cs = 1
      if (dma):
        omap2_mcspi_txrx_dma()
      else:
        omap2_mcspi_txrx_pio()
      if (cs_change) cs = 0
    end loop
  
    if (cs_active) cs = 0
    omap2_mcspi_set_enable(0)
  end loop


It seems that omap2_mcspi_set_enable() is called to enable the channel
(MCSPI_CHCTRLx[EN] is set) before force_cs() is called. If I'm
interpreting the hardware documentation correctly, the enable bit (among
other things) starts the SPI clock, meaning that the chip will begin
clocking out zeros to the device before CS is brought high.
Furthermore, even after CS is brought high, it seems there could be a
fair amount of time before the chip begins actually clocking out valid
data.

As I am writing this, it now occurs to me that perhaps the chip doesn't
start SPI_CLK until it has data to send. It seems that if this were the
case my concerns would be resolved. However, it is not at all clear that
this is the case from the documentation. When exactly does the
controller start the bus clock? Is this stated explicitly anywhere in
the documentation?

Any input you could offer would be greatly appreciated.
Thanks for your time.

- Ben


P.S. The more and more I think about it, it seems like my hypothesis is
the only logical behavior. It would be great if someone could confirm my
suspicions, however. It really seems like this should be in the
documentation either way.

P.P.S. I apologize if this is something someone familiar with SPI should
just know. My knowledge is a little spotty on this sort of thing.

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GPIO chip select support in McSPI

[Ben Gamari]

I've included the OMAP list so that I can hopefully get some feedback
from folks more familiar with this code.

Background:

I've been working on adding support for GPIO chip select lines to the
McSPI driver. Grant has been working with me to try getting the
in-kernel interface right and we have finally converged on a solution
whereby a table of GPIO lines will be passed to the McSPI driver through
platform_device.device.platform_data. Unfortunately, as explained below,
there is no clear path to support this in the current McSPI
initialization code.


On Thu, 03 Mar 2011 14:42:07 -0700, Grant Likely <grant.likely@secretlab.ca> wrote:
> The spi_master platform device is registered somewhere in the
> inappropriate support code. You need to arrange to make sure the
> correct pdata is attached to it when it gets registered. There
> /should/ be a mechanism for doing so.
> 
> All spi devices already specify a cs number anyway. What you can do is
> use the cs number as the lookup index into the gpio table, and
> remember to reserve a cs# for the 'native' cs line.
> 
I've done as you suggested and added support to the McSPI driver by
passing a GPIO table through platform_data. A patch will be coming
shortly.

Unfortunately, I'm really not sure how to restructure the OMAP code to
pass this information along. Currently the McSPI devices are registered
in arch/arm/mach-omap2/devices.c (omap_init_mcspi). In order to make the
GPIO CS support configurable by board code, we need some way to change
the (currently static) platform_devices prior to registration. Does
anyone have any suggestions on how this code could be refactored to
allow for this with minimal code duplication? Obviously we could just
move the platform_devices into the board files but this seems like a lot
of code duplication to support functionality that few boards will use.

Thoughts?

- Ben

[PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

Many applications require more chip select lines than the board or
processor allow. Introduce a mechanism to allow use of GPIO pins as
chip select lines with the McSPI controller. To use this functionality,
one simply provides a table mapping CS line numbers to GPIO numbers in
omap2_mcspi_platform_config.cs_gpios.

Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
---
 arch/arm/plat-omap/include/plat/mcspi.h |    3 ++-
 drivers/spi/omap2_mcspi.c               |   15 ++++++++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
index 1254e49..cac1d84 100644
--- a/arch/arm/plat-omap/include/plat/mcspi.h
+++ b/arch/arm/plat-omap/include/plat/mcspi.h
@@ -2,7 +2,8 @@
 #define _OMAP2_MCSPI_H
 
 struct omap2_mcspi_platform_config {
-	unsigned short	num_cs;
+	unsigned short num_cs;
+	int *cs_gpios;
 };
 
 struct omap2_mcspi_device_config {
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index abb1ffb..59cbed4 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 
 #include <linux/spi/spi.h>
+#include <linux/gpio.h>
 
 #include <plat/dma.h>
 #include <plat/clock.h>
@@ -235,11 +236,15 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
 
 static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
 {
-	u32 l;
-
-	l = mcspi_cached_chconf0(spi);
-	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
-	mcspi_write_chconf0(spi, l);
+	struct omap2_mcspi_platform_config *pconfig = spi->master->dev.platform_data;
+	if (pconfig->cs_gpios) {
+		int gpio = pconfig->cs_gpios[spi->chip_select];
+		gpio_set_value(gpio, cs_active);
+	} else {
+		u32 l = mcspi_cached_chconf0(spi);
+		MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
+		mcspi_write_chconf0(spi, l);
+	}
 }
 
 static void omap2_mcspi_set_master_mode(struct spi_master *master)
-- 
1.7.0.4

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Sun, Mar 13, 2011 at 03:05:19PM -0400, Ben Gamari wrote:
> Many applications require more chip select lines than the board or
> processor allow. Introduce a mechanism to allow use of GPIO pins as
> chip select lines with the McSPI controller. To use this functionality,
> one simply provides a table mapping CS line numbers to GPIO numbers in
> omap2_mcspi_platform_config.cs_gpios.
> 
> Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
> ---
>  arch/arm/plat-omap/include/plat/mcspi.h |    3 ++-
>  drivers/spi/omap2_mcspi.c               |   15 ++++++++++-----
>  2 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/plat-omap/include/plat/mcspi.h b/arch/arm/plat-omap/include/plat/mcspi.h
> index 1254e49..cac1d84 100644
> --- a/arch/arm/plat-omap/include/plat/mcspi.h
> +++ b/arch/arm/plat-omap/include/plat/mcspi.h
> @@ -2,7 +2,8 @@
>  #define _OMAP2_MCSPI_H
>  
>  struct omap2_mcspi_platform_config {
> -	unsigned short	num_cs;
> +	unsigned short num_cs;
> +	int *cs_gpios;
>  };
>  
>  struct omap2_mcspi_device_config {
> diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
> index abb1ffb..59cbed4 100644
> --- a/drivers/spi/omap2_mcspi.c
> +++ b/drivers/spi/omap2_mcspi.c
> @@ -35,6 +35,7 @@
>  #include <linux/slab.h>
>  
>  #include <linux/spi/spi.h>
> +#include <linux/gpio.h>
>  
>  #include <plat/dma.h>
>  #include <plat/clock.h>
> @@ -235,11 +236,15 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
>  
>  static void omap2_mcspi_force_cs(struct spi_device *spi, int cs_active)
>  {
> -	u32 l;
> -
> -	l = mcspi_cached_chconf0(spi);
> -	MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> -	mcspi_write_chconf0(spi, l);
> +	struct omap2_mcspi_platform_config *pconfig = spi->master->dev.platform_data;
> +	if (pconfig->cs_gpios) {
> +		int gpio = pconfig->cs_gpios[spi->chip_select];
> +		gpio_set_value(gpio, cs_active);
> +	} else {
> +		u32 l = mcspi_cached_chconf0(spi);
> +		MOD_REG_BIT(l, OMAP2_MCSPI_CHCONF_FORCE, cs_active);
> +		mcspi_write_chconf0(spi, l);
> +	}

What if the board wanted to use both the native SPI ss line as well as
one or more GPIOs?  You probably want to reserve cs0 for the native
gpio line.

Otherwise this patch looks good to me.

g.

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Ben Gamari]

On Mon, 14 Mar 2011 13:27:18 -0600, Grant Likely <grant.likely@secretlab.ca> wrote:
> What if the board wanted to use both the native SPI ss line as well as
> one or more GPIOs?  You probably want to reserve cs0 for the native
> gpio line.
> 
Hmm, I had thought about this and assumed it would be easiest to punt on
this, requiring the user to use the native line as a GPIO. This of
course assumes that all of the CS lines also have pinmux configurations
as GPIO pins. Is this not a good assumption? 

> Otherwise this patch looks good to me.
> 
Thanks!

- Ben

Re: [PATCH] mcspi: Add support for GPIO chip select lines

[Grant Likely]

On Mon, Mar 14, 2011 at 10:06:40PM -0400, Ben Gamari wrote:
> On Mon, 14 Mar 2011 13:27:18 -0600, Grant Likely <grant.likely@secretlab.ca> wrote:
> > What if the board wanted to use both the native SPI ss line as well as
> > one or more GPIOs?  You probably want to reserve cs0 for the native
> > gpio line.
> > 
> Hmm, I had thought about this and assumed it would be easiest to punt on
> this, requiring the user to use the native line as a GPIO. This of
> course assumes that all of the CS lines also have pinmux configurations
> as GPIO pins. Is this not a good assumption? 

As a general principle I would say no since it would mean adding a 2nd
GPIO device will potentially break the first if the infrastructure
isn't in place to handle the first line as a gpio.

g.