Enabling SPI1 and SPI3 on Linux (Naon)

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Naon am387x-dm814x.png Applies to Naon
Naon-evb-mid top.png Applies to NaonEVB-Mid
Tux.png Applies to Linux

Introduction[edit | edit source]

This article shows how to enable the SPI1 and SPI3 (with CS1 chip select) interfaces which can be used in a standard Linux application.

Pin Mux Option[edit | edit source]

SPI signals are available at different Naon pins. The configuration described below is dedicated to the NaonEVB-Mid carrier board, which provides the SPI1 and SPI3 signals at the J21 connector (please refer to NaonEVB-Mid wiki page for further details).

The following is the pin multiplexing configuration:

Signal Naon Connector Phisical Pin CPU Ball
SPI1_SCLK J1.34 AC3
SPI1_SCS1n J2.112 W6
SPI1_D0 J1.37 AA6
SPI1_D1 J1.90 AA3
SPI3_SCLK J2.99 AC26
SPI3_SCS1n J2.111 AG27
SPI3_D0 J2.89 V22
SPI3_D1 J2.87 AA25

U-Boot patch[edit | edit source]

200px-Emblem-important.svg.png The patches below applies to NELK 4.0.0 and above U-Boot source tree. 200px-Emblem-important.svg.png


The files board/dave/naon/pinmux_evb_mid.h must be modified according to the following patch:

diff --git a/board/dave/naon/pinmux_evb_mid.h b/board/dave/naon/pinmux_evb_mid.h
index ae21ca3..df3783f 100644
--- a/board/dave/naon/pinmux_evb_mid.h
+++ b/board/dave/naon/pinmux_evb_mid.h
@@ -45,7 +45,7 @@ MUX_VAL(PINCNTL3, (IEN | IPU | FCN1 )) /* SD1_DAT[0] */\
 MUX_VAL(PINCNTL4, (IEN | IPU | FCN1 )) /* SD1_DAT[1]_SDIRQ */\
 MUX_VAL(PINCNTL5, (IEN | IPU | FCN1 )) /* SD1_DAT[2]_SDRW */\
 MUX_VAL(PINCNTL6, (IEN | IPU | FCN1 )) /* SD1_DAT[3] */\
-MUX_VAL(PINCNTL7, (IEN | IPU | DISABLED )) /* safe_mode */\
+MUX_VAL(PINCNTL7, (IEN | IPU | FCN2 )) /* SPI[1]_SCS[1] */\
 MUX_VAL(PINCNTL8, (IEN | IPU | FCN1 )) /* SD0_CLK */\
 MUX_VAL(PINCNTL9, (IEN | IPU | FCN1 )) /* SD0_CMD */\
 MUX_VAL(PINCNTL10, (IEN | IPU | FCN1 )) /* SD0_DAT[0] */\
@@ -258,10 +258,10 @@ MUX_VAL(PINCNTL218, (IEN | IPD | DISABLED )) /* safe_mode */\
 MUX_VAL(PINCNTL219, (IEN | IPD | DISABLED )) /* safe_mode */\
 MUX_VAL(PINCNTL220, (IEN | IPD | DISABLED )) /* safe_mode */\
 MUX_VAL(PINCNTL221, (IEN | IPD | DISABLED )) /* safe_mode */\
-MUX_VAL(PINCNTL222, (IEN | IPD | DISABLED )) /* safe_mode */\
-MUX_VAL(PINCNTL223, (IEN | IPD | DISABLED )) /* safe_mode */\
-MUX_VAL(PINCNTL224, (IEN | IPD | DISABLED )) /* safe_mode */\
-MUX_VAL(PINCNTL225, (IEN | IPD | DISABLED )) /* safe_mode */\
+MUX_VAL(PINCNTL222, (IEN | IPU | FCN6 )) /* SPI[3]_SCS[1] */\
+MUX_VAL(PINCNTL223, (IEN | DIS | FCN6 )) /* SPI[3]_SCLK_MUX1 */\
+MUX_VAL(PINCNTL224, (IEN | DIS | FCN6 )) /* SPI[3]_D[1]_MUX1 */\
+MUX_VAL(PINCNTL225, (IEN | DIS | FCN6 )) /* SPI[3]_D[0]_MUX1 */\
 MUX_VAL(PINCNTL226, (IEN | IPD | DISABLED )) /* safe_mode */\
 MUX_VAL(PINCNTL227, (IEN | IPD | DISABLED )) /* safe_mode */\
 MUX_VAL(PINCNTL228, (IEN | IPU | FCN7 )) /* I2C[2]_SCL_MUX2 */\

U-Boot must be rebuilt to make these modifications effective.

Linux kernel patch[edit | edit source]

200px-Emblem-important.svg.png The patches below applies to NELK 4.0.0 and above Linux source tree. 200px-Emblem-important.svg.png


The files arch/arm/mach-omap2/board-naon.c and drivers/spi/omap2_mcspi.c must be modified according to the following patch:

diff --git a/arch/arm/mach-omap2/board-naon.c b/arch/arm/mach-omap2/board-naon.c
index 683af8e..e9d5023 100644
--- a/arch/arm/mach-omap2/board-naon.c
+++ b/arch/arm/mach-omap2/board-naon.c
@@ -794,6 +794,21 @@ struct spi_board_info __initdata naon_spi_slave_info[] = {
 		.chip_select	= 0,
 	},
 #endif
+
+        {
+            .modalias = "spidev",
+            .mode=SPI_MODE_0,
+            .max_speed_hz = 2000000,     /* max spiclock (SCK) speed in HZ */
+            .bus_num = 2,
+            .chip_select = 1,
+        },
+        {
+            .modalias = "spidev",
+            .mode=SPI_MODE_0,
+            .max_speed_hz = 2000000,     /* max spiclock (SCK) speed in HZ */
+            .bus_num = 4,
+            .chip_select = 1,
+        },
 };
 
 void __init naon_spi_init(void)
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 06f586e..848a8e7 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -1182,7 +1182,7 @@ static int __init omap2_mcspi_probe(struct platform_device *pdev)
 	case 4:
 		rxdma_id = spi4_rxdma_id;
 		txdma_id = spi4_txdma_id;
-		num_chipselect = 1;
+		num_chipselect = 2;
 		break;
 #endif
 	default:

Please note that SPI bus_num values to be used into the naon_spi_slave_info are:

  • SPI1: .bus_num = 2
  • SPI3: .bus_num = 4


The kernel must be rebuilt to make these modifications effective.

Using the interfaces[edit | edit source]

Users can access the peripherals connected to the SP1 and SPI3 buses through the spidev interface. For further information, please refer to

Patch download[edit | edit source]