Dose imx257 supports RTLinux?

[harihkumar]

I am using imx257 for linux-2.6.31. I want to use RTLinux In imx257.

Can you please let me know how to integrate RTLinux to imx257?

[fabio_estevam]

You could use a more recent kernel, such as 3.10 and aply the RT patches on top of it:

https://www.kernel.org/pub/linux/kernel/projects/rt/

Regards,

Fabio Estevam

[jppoulin]

Hi!  Has there been any development on RTLinux on the MX25 / MX28?

Has anyone been able to construct a robust RTLinux system on these Freescale chips?  (I do not see any Freescale chips listed in the 'tested RTLinux' platforms at https://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch#Platforms_Tested_and_in_Use_with_CONFIG...)

   Jean-Pierre

[fmvalero]

Currently, I have Linux 3.2.60 with RT patch applied running in my i.MX25 custom board. This is what I did (I assume LTIB and compiler gcc-4.4.4 are installed):

1. Download kernel from https://www.kernel.org/pub/linux/kernel/

2. Download RT patch for linux-3.2.60 from https://www.kernel.org/pub/linux/kernel/projects/rt/

3. Change compiler in PATH:

    Replace:  /opt/freescale/usr/local/gcc-4.1.2-glibc-2.5-nptl-3/arm-none-linux-gnueabi/bin/

    By:       /opt/freescale/usr/local/gcc-4.4.4-glibc-2.11.1-multilib-1.0/arm-fsl-linux-gnueabi/bin/

4. Set initial configuration:

   # make imx_v4_v5_defconfig

5. Go to kernel configuration:

   # make menuconfig

6. In Freescale MXC Implentations, select i.MX25 (all the other implementations must be unselected):

   System Type  --->

       Freescale MXC Implementations  --->

            Freescale CPU family --->

                 (X) i.MX1, i.MX21, i.MX25, i.MX27

                 ( ) i.MX3, i.MX6

                ( ) i.MX50, i.MX51, i.MX53

            [*] Support MX25PDK (3DS) Platform

       <*> Enable PWM driver

       [ ] Enable MXC debug board(for 3-stack) 

7. If you boot from Flash NAND, you have to edit the configuration file (.../linux-3.2.60/arch/arm/mach-imx/mach-mx25_3ds.c)

   Add:

  static struct mtd_partition mxc_nand_partitions[] = {

  {

  .name = "nand.bootloader",

  .offset = 0,

  .size = 3 * 1024 * 1024},

  {

  .name = "nand.kernel",

  .offset = MTDPART_OFS_APPEND,

  .size = 5 * 1024 * 1024},

  {

  .name = "nand.rootfs",

  .offset = MTDPART_OFS_APPEND,

  .size = 496 * 1024 * 1024},

  {

  .name = "nand.configure",

  .offset = MTDPART_OFS_APPEND,

  .size = 8 * 1024 * 1024},

  {

  .name = "nand.userfs",

  .offset = MTDPART_OFS_APPEND,

  .size = MTDPART_SIZ_FULL},

  };

This partition table have to be set according your NAND size (mine is 512MB). I my case, rootfs is flashed at offset 0x800000 (i have 3MB for bootloader space and 5MB for kernel). You need to adjust this to your case.

Modify the struct mxc_nand_platform_data to add the partition table:

  static const struct mxc_nand_platform_data mx25pdk_nand_board_info __initconst = {

       .width = 1,

       .hw_ecc = 1,

       .flash_bbt = 1,

       .parts = mxc_nand_partitions,

       .nr_parts = ARRAY_SIZE(mxc_nand_partitions),

  };

8. Compile kernel:

  # make uImage

9. Apply RT patch. From the folder where linux-3.2.60 is:

   # patch -p1 <../patch-3.2.60-rt87.patch

10. Go to kernel configuration again. Now, this can be selected:

     Kernel Features --->

       Preemption Model (Fully Preemptible Kernel (RT))--->

            ( ) No Forced Preemption (Server)

            ( ) Voluntary Kernel Preemption (Desktop)

            ( ) Preemptible Kernel (Low-Latency Desktop)

            ( ) Preemptible Kernel (Basic RT)

            (X) Fully Preemptible Kernel (RT)

11. Finally, compile again the kernel.

     # make uImage

This is the minimum you need to do to boot kernel. Later, you will need to modify configuration file to support all devices in your board.

Regards,

Fernando.

[jppoulin]

Thank you very much Fernando for the usable response.  Good news indeed! :smileyhappy: