* [patch 2.6.30] spi: new spi->mode bits
@ 2009-06-23 19:07 David Brownell
[not found] ` <200906231207.37879.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: David Brownell @ 2009-06-23 19:07 UTC (permalink / raw)
To: Andrew Morton, spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f
Cc: Paulraj, Sandeep
From: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
Add two new spi_device.mode bits to accomodate more protocol
options, and pass them through to usermode drivers:
* SPI_NO_CS ... a second 3-wire variant, where the chipselect
line is removed instead of a data line; transfers are still
full duplex.
This obviously has STRONG protocol implications since the
chipselect transitions can't be used to synchronize state
transitions with the SPI master.
* SPI_READY ... defines open drain signal that's pulled low
to pause the clock. This defines a 5-wire variant (normal
4-wire SPI plus READY) and two 4-wire variants (READY plus
each of the 3-wire flavors).
Such hardware flow control can be a big win. There are ADC
converters and flash chips that expose READY signals, but not
many host controllers support it today.
The spi_bitbang code should be changed to use SPI_NO_CS instead
of its current nonportable hack. That's a mode most hardware
can easily support (unlike SPI_READY).
Signed-off-by: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
---
An upcoming driver for the SPI controller in some new DaVinci
family chips (the DA830/OMAP-L137) supports both these modes.
Yep, and later patches will add more spi_device.mode bits, now
that the existing set is all used up.
Documentation/spi/spidev_test.c | 10 +++++++++-
drivers/spi/spidev.c | 17 +++++++++++------
include/linux/spi/spi.h | 2 ++
include/linux/spi/spidev.h | 2 ++
4 files changed, 24 insertions(+), 7 deletions(-)
--- a/Documentation/spi/spidev_test.c
+++ b/Documentation/spi/spidev_test.c
@@ -99,11 +99,13 @@ void parse_opts(int argc, char *argv[])
{ "lsb", 0, 0, 'L' },
{ "cs-high", 0, 0, 'C' },
{ "3wire", 0, 0, '3' },
+ { "no-cs", 0, 0, 'N' },
+ { "ready", 0, 0, 'R' },
{ NULL, 0, 0, 0 },
};
int c;
- c = getopt_long(argc, argv, "D:s:d:b:lHOLC3", lopts, NULL);
+ c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
if (c == -1)
break;
@@ -139,6 +141,12 @@ void parse_opts(int argc, char *argv[])
case '3':
mode |= SPI_3WIRE;
break;
+ case 'N':
+ mode |= SPI_NO_CS;
+ break;
+ case 'R':
+ mode |= SPI_READY;
+ break;
default:
print_usage(argv[0]);
break;
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -58,15 +58,20 @@ static unsigned long minors[N_SPI_MINORS
/* Bit masks for spi_device.mode management. Note that incorrect
- * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
- * devices on a shared bus: CS_HIGH, because this device will be
- * active when it shouldn't be; 3WIRE, because when active it won't
- * behave as it should.
+ * settings for some settings can cause *lots* of trouble for other
+ * devices on a shared bus:
*
- * REVISIT should changing those two modes be privileged?
+ * - CS_HIGH ... this device will be active when it shouldn't be
+ * - 3WIRE ... when active, it won't behave as it should
+ * - NO_CS ... there will be no explicit message boundaries; this
+ * is completely incompatible with the shared bus model
+ * - READY ... transfers may proceed when they shouldn't.
+ *
+ * REVISIT should changing those flags be privileged?
*/
#define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
- | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
+ | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
+ | SPI_NO_CS | SPI_READY)
struct spidev_data {
dev_t devt;
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -80,6 +80,8 @@ struct spi_device {
#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
#define SPI_3WIRE 0x10 /* SI/SO signals shared */
#define SPI_LOOP 0x20 /* loopback mode */
+#define SPI_NO_CS 0x40 /* 1 dev/bus, no chipselect */
+#define SPI_READY 0x80 /* slave pulls low to pause */
u8 bits_per_word;
int irq;
void *controller_state;
--- a/include/linux/spi/spidev.h
+++ b/include/linux/spi/spidev.h
@@ -40,6 +40,8 @@
#define SPI_LSB_FIRST 0x08
#define SPI_3WIRE 0x10
#define SPI_LOOP 0x20
+#define SPI_NO_CS 0x40
+#define SPI_READY 0x80
/*---------------------------------------------------------------------------*/
------------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch 2.6.30] spi: new spi->mode bits
[not found] ` <200906231207.37879.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
@ 2009-06-23 19:15 ` Andrew Morton
[not found] ` <20090623121555.065876b2.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2009-06-23 19:15 UTC (permalink / raw)
To: David Brownell
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f,
s-paulraj-l0cyMroinI0
On Tue, 23 Jun 2009 12:07:37 -0700
David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> wrote:
> Subject: [patch 2.6.30] spi: new spi->mode bits
2.6.31, I assume.
It's a bit late for 2.6.31 really, but this looks harmless enough.
------------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch 2.6.30] spi: new spi->mode bits
[not found] ` <20090623121555.065876b2.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
@ 2009-06-23 19:44 ` David Brownell
0 siblings, 0 replies; 3+ messages in thread
From: David Brownell @ 2009-06-23 19:44 UTC (permalink / raw)
To: Andrew Morton
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f,
s-paulraj-l0cyMroinI0
On Tuesday 23 June 2009, Andrew Morton wrote:
> On Tue, 23 Jun 2009 12:07:37 -0700
> David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> wrote:
>
> > Subject: [patch 2.6.30] spi: new spi->mode bits
>
> 2.6.31, I assume.
>
> It's a bit late for 2.6.31 really, but this looks harmless enough.
Yeah, 2.6.31 would be good ... I thought I'd sent this before,
evidently not.
------------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-06-23 19:07 [patch 2.6.30] spi: new spi->mode bits David Brownell
[not found] ` <200906231207.37879.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2009-06-23 19:15 ` Andrew Morton
[not found] ` <20090623121555.065876b2.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2009-06-23 19:44 ` David Brownell
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