McSPI and DMA on OMAP4430

Josua Purba76

Other Parts Discussed in Thread: 4430

Dear all,

I'm a newbie on Omap 4430 with linux and I hope this is the correct place to ask. I use Duovero (OMAP 4430) with kernel 3.6 and yocto 1.4 (Dylan) from gumstix repo:

github.com/.../Gumstix-YoctoProject-Repo

I have been reading threads related to SPI but my questions is more basic and fundamental:

https://e2e.ti.com/support/embedded/linux/f/354/t/259974

http://gumstix.8.x6.nabble.com/SPI-and-multi-threading-issue-td4969428.html

gumstix.8.x6.nabble.com/SPI-problem-on-Overo-td4966514.html

gumstix.8.x6.nabble.com/McSPI-input-DMA-threshold-td4966954.html

https://e2e.ti.com/support/arm/sitara_arm/f/791/t/188833

I enable DMA and McSPI from kernel menuconfig and by default McSPI is in single-channel master mode.

My application implements bidirectional communications using spidev and SPI_IOC_MESSAGE ioctl call.

I follow similar thread on pandaboard (since it use OMAP4) on:

https://groups.google.com/forum/#!msg/pandaboard/vg1tE8HABb0/mYQmQejAA-wJ.

I modify its code for my board as follows:

On board-duovero.c (under …/arch/arm/mach-omap2/) I add the following code:

static struct omap2_mcspi_device_config spidev_mcspi_config = {

.turbo_mode = 0,

.single_channel = 1, /* 0: slave, 1: master */

};

static struct spi_board_info duovero_spi_board_info[] __initdata = {

{

.modalias = "spidev",

.bus_num = 1,

.chip_select = 0,

.max_speed_hz = 48000000,

.mode = SPI_MODE_0,

.controller_data = &spidev_mcspi_config,

{

.modalias = "spidev",

.bus_num = 4,

.chip_select = 0,

.max_speed_hz = 48000000,

.mode = SPI_MODE_0,

.controller_data = &spidev_mcspi_config,

};

static int __init duovero_spi_init(void){

spi_register_board_info(duovero_spi_board_info, ARRAY_SIZE(duovero_spi_board_info));

omap_mux_init_signal("mcspi1_clk.mcspi1_clk", OMAP_PIN_INPUT | OMAP_MUX_MODE0);

omap_mux_init_signal("mcspi1_somi.mcspi1_somi", OMAP_PIN_INPUT | OMAP_MUX_MODE0);

omap_mux_init_signal("mcspi1_simo.mcspi1_simo", OMAP_PIN_OUTPUT | OMAP_MUX_MODE0);

omap_mux_init_signal("mcspi1_cs0.mcspi1_cs0", OMAP_PIN_OUTPUT| OMAP_MUX_MODE0);

return 0;

}

On duovero_init I add duovero_spi_init(). I can see during linux boot up that McSPI and DMA are initialized.

My questions are as follows:

1. Do I initialized the spi and McSPI correctly? Does the pin mux correct for Duovero?

2. I run loop back (connect MOSI with MISO) with spidev test code on:

https://www.kernel.org/doc/Documentation/spi/spidev_test.c

and I can see it works for 2 channels.

However, I’m not sure it uses McSPI + DMA since I check the CPU utilization are more less the same with and without McSPI + DMA.

How can I make user space code to exercise McSPI + DMA correctly?

Could someone please give me some hint on code to exercise McSPI + DMA?.

I know spi-omap2-mcspi.c provides drivers for McSPI.

Any help from anyone would be appreciated.

Thank you,

Josua Purba

over 9 years ago

0 Yanko Todorov-XID over 9 years ago

TI__Mastermind 29520 points

Hello Josua,

#Q1. Do I initialized the spi and McSPI correctly? Does the pin mux correct for Duovero?

You can check pin mux configuration by pad control registers in control module:

CONTROL_CORE_PAD0_I2C4_SDA_PAD1_MCSPI1_CLK[18:16] MCSPI1_CLK_MUXMODE - 0x0: Select mcspi1_clk

CONTROL_CORE_PAD0_MCSPI1_SOMI_PAD1_MCSPI1_SIMO[2:0] MCSPI1_SOMI_MUXMODE - 0x0: Select mcspi1_somi

CONTROL_CORE_PAD0_MCSPI1_SOMI_PAD1_MCSPI1_SIMO[18:16] MCSPI1_SIMO_MUXMODE - 0x0: Select mcspi1_simo

CONTROL_CORE_PAD0_MCSPI1_CS0_PAD1_MCSPI1_CS1[2:0] MCSPI1_CS0_MUXMODE - 0x0: Select mcspi1_cs0

CONTROL_CORE_PAD0_MCSPI1_CS0_PAD1_MCSPI1_CS1[18:16] MCSPI1_CS1_MUXMODE - 0x0: Select mcspi1_cs1

CONTROL_CORE_PAD0_MCSPI1_CS2_PAD1_MCSPI1_CS3[2:0] MCSPI1_CS2_MUXMODE - 0x0: Select mcspi1_cs2

CONTROL_CORE_PAD0_MCSPI1_CS2_PAD1_MCSPI1_CS3[18:16] MCSPI1_CS3_MUXMODE - 0x0: Select mcspi1_cs3

Take a look on this wiki - http://wiki.gumstix.org/index.php?title=Duovero_Multiplexes

#Q2. I run loop back (connect MOSI with MISO) with spidev test code on:

https://www.kernel.org/doc/Documentation/spi/spidev_test.c and I can see it works for 2 channels.

However, I’m not sure it uses McSPI + DMA since I check the CPU utilization are more less the same with and without McSPI + DMA.

Every McSPI module supports two DMA requests (read/write) per channel. Two DMA request events (read and write) allow synchronized accesses of the DMA controller with the activity of MCSPI.

DMA request events, read and write, synchronize read/write accesses of the DMA controller with the activity of MCSPI. DMA requests are asserted using the registers: SPIm.MCSPI_CHxCONF[15] DMAR bit (where x = 0) for reading and the SPIm.MCSPI_CHxCONF[14] DMAW bit (where x = 0) for writing.

I suggest you to see in file - kernel-ubuntu/drivers/spi/spi-omap2-mcspi.c

214 static void omap2_mcspi_set_dma_req(const struct spi_device *spi,
215                 int is_read, int enable)
216 {
217         u32 l, rw;
218 
219         l = mcspi_cached_chconf0(spi);
220 
221         if (is_read) /* 1 is read, 0 write */
222                 rw = OMAP2_MCSPI_CHCONF_DMAR;
223         else
224                 rw = OMAP2_MCSPI_CHCONF_DMAW;
225 
226         if (enable)
227                 l |= rw;
228         else
229                 l &= ~rw;
230 
231         mcspi_write_chconf0(spi, l);
232 }

http://lxr.free-electrons.com/source/drivers/spi/spi-omap2-mcspi.c

#Q3: How can I make user space code to exercise McSPI + DMA correctly?

Please take a look on this link - http://elinux.org/BeagleBoard/SPI

#Q4: Could someone please give me some hint on code to exercise McSPI + DMA?.

This wiki www.omappedia.com/.../PandaBoard_SPI describes details about development of userspace API with SPI. See section Accessing device.

Best regards,

Yanko

0 Josua Purba76 over 9 years ago in reply to Yanko Todorov-XID

Prodigy 20 points

Hi Yanko,
Thank you so much for your response and I'll try it.

Actually, I have another issue with USB Host when I did McSPI and DMA.
It does not show up whenever I enable McSPI+DMA. This is similar issue like:
e2e.ti.com/.../1291227
I'm not sure why. Is there any conflict among them?

Thank you,
Josua Purba

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McSPI and DMA on OMAP4430