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This version (28 Dec 2020 06:57) was approved by Sunny Feng.

Table of Contents

SRAM driver

Introduction

This page introduces the SRAM driver in ADI linux kernel for sc5xx ezkit boards. Users could allocate memory from specified sram pool defined in dts. sram_mmap driver in this page is an example for this. For how to enable the sram_mmap, please see the below sections.

Package Configuration

vim conf/local.conf
IMAGE_INSTALL_append = " sram-mmap-test"

Kernel config

Disable icc driver

bitbake linux-adi -c menuconfig
Device Drivers  --->
       [*] Staging drivers  --->
             [N]   icc driver  ----

Enable sram driver

bitbake linux-adi -c menuconfig
Device Drivers  --->
       Misc devices  --->
            [*] Generic on-chip SRAM driver
            [*] MMAP driver for sc5xx onchip SRAM
            [*] /proc/sraminfo support for sc5xx onchip SRAM

Test Example

# sram_mmap /dev/sram_mmap
sram mmaped 0x20084000 : 0x20085000 successfully!
mmap pass.
# cat /proc/sraminfo
sram-icc@20080000:
Total size: 4 KB
Used sram: 0 KB
Avail sram: 4 KB
sram-reserved@20084000:
Total size: 236 KB
Used sram: 0 KB
Avail sram: 236 KB

SRAM driver

There are two main c files under the driver/sram/adi directory.

sram.c
will create a /proc/sraminfo in filesytem, control/monitor the sram memory, use the command “#cat /proc/sraminfo”
sram_mmap.c
one example to use the sram framework, allocate memory from the specified pool defined in dts, and then free the memory

Reserved SRAM pools in dts file

These 2 dts part will generate 2 memory pools from sram using “mmio-sram” driver. 

sram0: sram-icc@20080000 { /* ICC SRAM 4KB */
    compatible = "mmio-sram";
    #address-cells = <1>;
    #size-cells = <1>;
    reg = <0x20080000 0x1000>;
    ranges = <0 0x20080000 0x1000>;
};
 
sram1: sram-reserved@20084000 {
    compatible = "mmio-sram";
    #address-cells = <1>;
    #size-cells = <1>;
    reg = <0x20084000 0x3B000>;
    ranges = <0 0x20084000 0x3B000>;
};

How to add another device to use the memory in sram

If users want to allocate their own sram memory from sram pool in linux kernel, they should first

  1. add below line dts in your own device
adi,sram = <&sram1>;
  1. Add below code in your device driver source code
/* Get the sram pool from dts */
sram_pool = of_gen_pool_get(dev->of_node, "adi,sram", 0);
if (!sram_pool) {
        pr_err("Unable to get sram pool!\n");
        return -ENODEV;
}
 
/* Get the allocated virtual memory from sram pool */
vaddr = gen_pool_alloc(sram_pool, sram_size);
if (!vaddr) {
    pr_warn("Faied to alloc sram from sram pool!\n");
}
 
/* Remember: When you finish all the operations, free the allocated addr */
gen_pool_free(sram_pool, vaddr, sram_size);


Back to Kernel Features and Device Drivers for ADSP-SC5xx Yocto Linux

resources/tools-software/linuxdsp/docs/linux-kernel-and-drivers/sram.txt · Last modified: 28 Dec 2020 06:56 by Sunny Feng

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