Re: SPI troubles

[Philip Balister <philip@balister.org>]

On 03/14/2010 10:44 PM, Ben Gamari wrote:
> Hey all,
>
> As I've mentioned here in the past, I am currently putting together a board for
> doing analog data acquisition on the BeagleBoard platform. Unfortunately, I
> have wasted nearly the entire weekend trying to accomplish the (one would
> think) simple goal of recieving data with the McSPI controllers (in particular,
> run a loop-back test on McSPI3 with spidev_test).

For some reason you need to set the clock pin as an input. Here is the 
config for mcspi1 that is working for me:

MUX_VAL(CP(MCSPI1_CLK),         (IEN  | PTD | DIS | M0)) /*McSPI1_CLK*/\

(from u-boot)

Philip



>
> While I can reliably see a signal sent on the SIMO line, I have not once been
> able to recieve anything but zeros in return. I have verified that the the SOMI
> ball works as expected as a GPIO input. I have tried every pinmux configuration
> imaginable (using both the kernel and u-boot) and yet I have still met no
> success. It seems like this has been an issue in the past[1] and it seems that
> at one point SPI was working[2], yet I have been completely unable to reproduce
> this result.
>
> When measuring the SIMO signal on the expansion connector with my daughterboard
> connected, I noticed that the daughterboard's level shifter appeared to be
> driving the signal higher than it should, to ~2.9 Volts. I then checked the
> 1.8V rail voltage and found that it too was higher than expected, again at 2.9
> volts. When I unplug the daughterboard, the 1.8V rail voltage returns to its
> expected value.
>
> I'm both perplexed and concerned with this behavior. I completely fail to
> see how my board is raising the voltage on the 1.8V rail (schematic available
> at [3]).  While the BeagleBoard seems quite stable, I'm very concerned that
> perhaps the daughterboard over-drove the SIMO ball and burned out some subset
> of the OMAP.  Regardless, as mentioned earlier, I have verified the
> functionality of the same ball as a GPIO input. Thus, I am thoroughly confused.
> Is it possible that the ball's GPIO receiver could remain functional while the
> McSPI receiver is burned out?
>
> I am using a 2.6.32 kernel and can see in debugfs that the pinmux is configured
> correct, with only the sdmmc2_dat0 pin exposing the McSPI3_SOMI signal. The
> kernel patch I'm using to configure the muxes and spi controllers is included
> below. As can be seen, I've also tried using the spi-gpio driver, but
> unfortunately I wasn't even able to get it producing data on SIMO.
>
> I've tried this using two daughterboards on two different Beagles (a B7 and a
> new C4) with identical results on both.  If anyone has any ideas at all, I would
> love to hear them. I am really unsure of how to proceed at this point and I'm
> quickly running out of time to devote to this project. I've included my kernel
> patch below and the daughterboard design is available in Eagle format at [3].
>
> Thanks,
>
> - Ben
>
>
> P.S. It seems to me that SPI is one of the more important interfaces on the
> BoardBoard. As such, it would be really nice if there was a standard test of
> SPI functionality. It seems many people have struggled to get SPI working on
> the BeagleBoard and not too many have succeeded. A standard prescription would
> be extremely useful.
>
> P.P.S. Is it just me or does the omap_pinmux interface need some refinement.
> Using it has been an exercise in frustration, between extremely sparse
> documentation, quirky behavior (I still haven't figure out how to get gpio_130
> configured.  omap_mux_init_gpio fails with "multiple paths for gpio130" whereas
> omap_mux_init_signal fails to even recognize the signal name), and general
> complexity. The idea behind the interface seems excellent, but it seems it
> hasn't been used enough not to be a complete pain in the ass to figure out and
> use.
>
>
> [1] http://markmail.org/message/2vbfuz7bltvrk6g3#query:beagle%20spi%20zeros+page:1+mid:wduqfhs4ur373ehp+state:results
> [2] http://groups.google.com/group/beagleboard/browse_thread/thread/42988f0e14db0f01/816397901ec999c4?lnk=gst&q=Balister+&pli=1
> [3] http://goldnerlab.physics.umass.edu/git?p=tracker-board.git;a=summary
>
>
>
> diff --git a/arch/arm/mach-omap2/board-omap3beagle.c b/arch/arm/mach-omap2/board-omap3beagle.c
> index 231cb4e..b23c5a5 100644
> --- a/arch/arm/mach-omap2/board-omap3beagle.c
> +++ b/arch/arm/mach-omap2/board-omap3beagle.c
> @@ -12,6 +12,10 @@
>    * published by the Free Software Foundation.
>    */
>
> +//#define BEAGLE_GPIO_SPI
> +
> +
> +
>   #include<linux/kernel.h>
>   #include<linux/init.h>
>   #include<linux/platform_device.h>
> @@ -28,6 +32,7 @@
>   #include<linux/mtd/partitions.h>
>   #include<linux/mtd/nand.h>
>
> +#include<linux/spi/spi.h>
>   #include<linux/regulator/machine.h>
>   #include<linux/i2c/twl.h>
>
> @@ -372,6 +377,159 @@ static struct platform_device *omap3_beagle_devices[] __initdata = {
>   	&keys_gpio,
>   };
>
> +#ifndef BEAGLE_GPIO_SPI
> +
> +static void __init omap3_beagle_config_mcspi3_mux(void)
> +{
> +	omap_mux_init_signal("sdmmc2_clk.mcspi3_clk", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("sdmmc2_dat3.mcspi3_cs0", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("sdmmc2_dat2.mcspi3_cs1", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("sdmmc2_cmd.mcspi3_simo", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("sdmmc2_dat0.mcspi3_somi", OMAP_PIN_INPUT_PULLUP);
> +}
> +
> +static void __init omap3_beagle_config_mcspi4_mux(void)
> +{
> +	omap_mux_init_signal("mcbsp1_clkr.mcspi4_clk", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("mcbsp1_fsx.mcspi4_cs0", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("mcbsp1_dx.mcspi4_simo", OMAP_PIN_OUTPUT);
> +	omap_mux_init_signal("mcbsp1_dr.mcspi4_somi", OMAP_PIN_INPUT_PULLUP);
> +}
> +
> +static struct spi_board_info beagle_mcspi_board_info[] = {
> +	// spi 3.0
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 3,
> +		.chip_select	= 0,	
> +		.mode = SPI_MODE_1,
> +	},
> +
> +	// spi 3.1
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 3,
> +		.chip_select	= 1,	
> +		.mode = SPI_MODE_1,
> +	},
> +
> +	// spi 4.0
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 4,
> +		.chip_select	= 0,	
> +		.mode = SPI_MODE_1,
> +	},
> +};
> +
> +#else /* BEAGLE_GPIO_SPI */
> +#include<linux/spi/spi_gpio.h>
> +
> +#define SPI3_CLK 130
> +#define SPI3_SOMI 132
> +#define SPI3_SIMO 131
> +#define SPI3_CS0 135
> +#define SPI3_CS1 134
> +
> +#define SPI4_CLK 156
> +#define SPI4_SOMI 159
> +#define SPI4_SIMO 158
> +#define SPI4_CS0 161
> +
> +#define GPIO_SPI_PIN(pin, dir, name)  \
> +	omap_mux_init_gpio(pin, OMAP_PIN_##dir); \
> +	gpio_request(pin, name); \
> +	gpio_export(pin, true);
> +
> +static void __init omap3_beagle_config_gpio_spi3_mux(void)
> +{
> +	GPIO_SPI_PIN(SPI3_CLK, OUTPUT, "spi3_clk");
> +	GPIO_SPI_PIN(SPI3_SIMO, OUTPUT, "spi3_simo");
> +	GPIO_SPI_PIN(SPI3_SOMI, INPUT, "spi3_somi");
> +	GPIO_SPI_PIN(SPI3_CS0, OUTPUT, "spi3_cs0");
> +	GPIO_SPI_PIN(SPI3_CS1, OUTPUT, "spi3_cs1");
> +}
> +
> +static void __init omap3_beagle_config_gpio_spi4_mux(void)
> +{
> +	GPIO_SPI_PIN(SPI4_CLK, OUTPUT, "spi4_clk");
> +	GPIO_SPI_PIN(SPI4_SIMO, OUTPUT, "spi4_simo");
> +	GPIO_SPI_PIN(SPI4_SOMI, INPUT, "spi4_somi");
> +	GPIO_SPI_PIN(SPI4_CS0, OUTPUT, "spi4_cs0");
> +}
> +
> +static struct spi_gpio_platform_data beagle_gpio_spi_platform_data[] = {
> +	// spi 3
> +	{
> +		.sck = SPI3_CLK,
> +		.miso = SPI3_SOMI,
> +		.mosi = SPI3_SIMO,
> +		.num_chipselect = 2,
> +	},
> +
> +	// spi 4
> +	{
> +		.sck = SPI4_CLK,
> +		.miso = SPI4_SOMI,
> +		.mosi = SPI4_SIMO,
> +		.num_chipselect = 1,
> +	},
> +};
> +
> +static struct platform_device beagle_gpio_spi_platform_device[] = {
> +	// spi .
> +	{
> +		.name		= "spi_gpio",
> +		.id		= 3,
> +		.dev		= {
> +			.platform_data =&beagle_gpio_spi_platform_data[0],
> +		},
> +	},
> +
> +	// spi 4
> +	{
> +		.name		= "spi_gpio",
> +		.id		= 4,
> +		.dev		= {
> +			.platform_data =&beagle_gpio_spi_platform_data[1],
> +		},
> +	},
> +};
> +
> +static struct spi_board_info beagle_gpio_spi_board_info[] = {
> +	// spi 3.0
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 3,
> +		.mode = SPI_MODE_1,
> +		.controller_data = (void *) SPI3_CS0,
> +	},
> +
> +	// spi 3.1
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 3,
> +		.mode = SPI_MODE_1,
> +		.controller_data = (void *) SPI3_CS1,
> +	},
> +
> +	// spi 4.0
> +	{
> +		.modalias	= "spidev",
> +		.max_speed_hz	= 48000000, //48 Mbps
> +		.bus_num	= 4,
> +		.mode = SPI_MODE_1,
> +		.controller_data = (void *) SPI4_CS0,
> +	},
> +};
> +
> +#endif /* BEAGLE_GPIO_SPI */
> +
>   static void __init omap3beagle_flash_init(void)
>   {
>   	u8 cs = 0;
> @@ -432,12 +590,30 @@ static struct omap_board_mux board_mux[] __initdata = {
>
>   static void __init omap3_beagle_init(void)
>   {
> +	int i;
> +
>   	omap3_mux_init(board_mux, OMAP_PACKAGE_CBB);
>   	omap3_beagle_i2c_init();
>   	platform_add_devices(omap3_beagle_devices,
>   			ARRAY_SIZE(omap3_beagle_devices));
>   	omap_serial_init();
>
> +#ifndef BEAGLE_GPIO_SPI
> +	printk(KERN_ERR "Using McSPI for SPI\n");
> +	omap3_beagle_config_mcspi3_mux();
> +	omap3_beagle_config_mcspi4_mux();
> +	spi_register_board_info(beagle_mcspi_board_info,
> +			ARRAY_SIZE(beagle_mcspi_board_info));
> +#else
> +	printk(KERN_ERR "Using GPIO for SPI\n");
> +	omap3_beagle_config_gpio_spi3_mux();
> +	omap3_beagle_config_gpio_spi4_mux();
> +	for (i=0; i<3; i++)
> +		platform_device_register(&beagle_gpio_spi_platform_device[i]);
> +	spi_register_board_info(beagle_gpio_spi_board_info,
> +			ARRAY_SIZE(beagle_gpio_spi_board_info));
> +#endif
> +
>   	omap_mux_init_gpio(170, OMAP_PIN_INPUT);
>   	gpio_request(170, "DVI_nPD");
>   	/* REVISIT leave DVI powered down until it's needed ... */
> @@ -458,6 +634,7 @@ static void __init omap3_beagle_map_io(void)
>   	omap2_map_common_io();
>   }
>
> +
>   MACHINE_START(OMAP3_BEAGLE, "OMAP3 Beagle Board")
>   	/* Maintainer: Syed Mohammed Khasim - http://beagleboard.org */
>   	.phys_io	= 0x48000000,
> --
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