rk3399下spi驅動
SPI 使用
Note:本文從firefly wiki擷取
SPI是一種高速的,全雙工,同步序列通訊介面,用於連線微控制器、感測器、儲存裝置等。 Firefly-RK3399 開發板提供了 SPI1 (單片選)介面,具體位置如下圖:
SPI工作方式
SPI以主從方式工作,這種模式通常有一個主裝置和一個或多個從裝置,需要至少4根線,分別是:
CS 片選訊號 SCLK 時鐘訊號 MOSI 主裝置資料輸出、從裝置資料輸入 MISO 主裝置資料輸入,從裝置資料輸出
Linux核心用CPOL和CPHA的組合來表示當前SPI的四種工作模式:
CPOL=0,CPHA=0 SPI_MODE_0 CPOL=0,CPHA=1 SPI_MODE_1 CPOL=1,CPHA=0 SPI_MODE_2 CPOL=1,CPHA=1 SPI_MODE_3
CPOL:表示時鐘訊號的初始電平的狀態,0為低電平,1為高電平。CPHA:表示在哪個時鐘沿取樣,0為第一個時鐘沿取樣,1為第二個時鐘沿取樣。SPI的四種工作模式波形圖如下:
驅動編寫
下面以 W25Q128FV Flash模組為例簡單介紹SPI驅動的編寫。
硬體連線
Firefly-RK3399 與 W25Q128FV 硬體連線如下表:
編寫Makefile/Kconfig
在kernel/drivers/spi/Kconfig中新增對應的驅動檔案配置:
config SPI_FIREFLY tristate "Firefly SPI demo support " default y help Select this option if your Firefly board needs to run SPI demo.
在kernel/drivers/spi/Makefile中新增對應的驅動檔名:
obj-$(CONFIG_SPI_FIREFLY) += spi-firefly-demo.o
config中選中所新增的驅動檔案,如:
│ Symbol: SPI_FIREFLY [=y] │ Type : tristate │ Prompt: Firefly SPI demo support │ Location: │ -> Device Drivers │ -> SPI support (SPI [=y]) │ Defined at drivers/spi/Kconfig:704 │ Depends on: SPI [=y] && SPI_MASTER [=y]
配置DTS節點
在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-demo.dtsi中新增SPI驅動結點描述,如下所示:
/* Firefly SPI demo */
&spi1 {
spi_demo: [email protected]{
status = "okay";
compatible = "firefly,rk3399-spi";
reg = <0x00>;
spi-max-frequency = <48000000>;
/* rk3399 driver support SPI_CPOL | SPI_CPHA | SPI_CS_HIGH */
//spi-cpha; /* SPI mode: CPHA=1 */
//spi-cpol; /* SPI mode: CPOL=1 */
//spi-cs-high;
};
};
&spidev0 {
status = "disabled";
};
- status:如果要啟用SPI,則設為okay,如不啟用,設為disable。
- [email protected]:由於本例子使用CS0,故此處設為00,如果使用CS1,則設為01。
- compatible:這裡的屬性必須與驅動中的結構體:of_device_id 中的成員compatible 保持一致。
- reg:此處與[email protected]保持一致,本例設為:0x00。
- spi-max-frequency:此處設定spi使用的最高頻率。Firefly-RK3399最高支援48000000。
- spi-cpha,spi-cpol:SPI的工作模式在此設定,本例所用的模組SPI工作模式為SPI_MODE_0或者SPI_MODE_3,這裡我們選用SPI_MODE_0,如果使用SPI_MODE_3,spi_demo中開啟spi-cpha和spi-cpol即可。
- spidev0: 由於spi_demo與spidev0使用一樣的硬體資源,需要把spidev0關掉才能開啟spi_demo
定義SPI驅動
在核心原始碼目錄kernel/drivers/spi/中建立新的驅動檔案,如:spi-firefly-demo.c 在定義 SPI 驅動之前,使用者首先要定義變數 of_device_id 。 of_device_id 用於在驅動中呼叫dts檔案中定義的裝置資訊,其定義如下所示:
static struct of_device_id firefly_match_table[] = {{ .compatible = "firefly,rk3399-spi",},{},};
此處的compatible與DTS檔案中的保持一致。
spi_driver定義如下所示:
static struct spi_driver firefly_spi_driver = {
.driver = {
.name = "firefly-spi",
.owner = THIS_MODULE,
.of_match_table = firefly_match_table,},
.probe = firefly_spi_probe,};
註冊SPI裝置
在初始化函式static int __init spidev_init(void)中向核心註冊SPI驅動: spi_register_driver(&firefly_spi_driver);
如果核心啟動時匹配成功,則SPI核心會配置SPI的引數(mode、speed等),並呼叫firefly_spi_probe。
讀寫 SPI 資料
Note:程式在文末
firefly_spi_probe中使用了兩種介面操作讀取W25Q128FV的ID: firefly_spi_read_w25x_id_0介面直接使用了spi_transfer和spi_message來傳送資料。 firefly_spi_read_w25x_id_1介面則使用SPI介面spi_write_then_read來讀寫資料。
成功後會列印:
[email protected]_firefly_box:/ # dmesg | grep firefly-spi
[ 1.006235] firefly-spi spi0.0: Firefly SPI demo program
[ 1.006246] firefly-spi spi0.0: firefly_spi_probe: setup mode 0, 8 bits/w, 48000000 Hz max
[ 1.006298] firefly-spi spi0.0: firefly_spi_read_w25x_id_0: ID = ef 40 18 00 00
[ 1.006361] firefly-spi spi0.0: firefly_spi_read_w25x_id_1: ID = ef 40 18 00 00
開啟SPI demo
spi-firefly-demo預設沒有開啟,如果需要的話可以使用以下補丁開啟demo驅動:
--- a/kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-demo.dtsi
+++ b/kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-demo.dtsi
@@ -64,7 +64,7 @@ /* Firefly SPI demo */
&spi1 {spi_demo: [email protected]{
- status = "disabled";
+ status = "okay";
compatible = "firefly,rk3399-spi";
reg = <0x00>;
spi-max-frequency = <48000000>;
@@ -76,6 +76,6 @@
};
&spidev0 {
- status = "okay";
+ status = "disabled";
};
常用SPI介面
下面是常用的 SPI API 定義:
void spi_message_init(struct spi_message *m);
void spi_message_add_tail(struct spi_transfer *t, struct spi_message *m);
int spi_sync(struct spi_device *spi, struct spi_message *message) ;
int spi_write(struct spi_device *spi, const void *buf, size_t len);
int spi_read(struct spi_device *spi, void *buf, size_t len);
ssize_t spi_w8r8(struct spi_device *spi, u8 cmd);
ssize_t spi_w8r16(struct spi_device *spi, u8 cmd);
ssize_t spi_w8r16be(struct spi_device *spi, u8 cmd);
int spi_write_then_read(struct spi_device *spi, const void *txbuf, unsigned n_tx, void *rxbuf, unsigned n_rx);
介面使用
Linux提供了一個功能有限的SPI使用者介面,如果不需要用到IRQ或者其他核心驅動介面,可以考慮使用介面spidev編寫使用者層程式控制SPI裝置。 在 Firefly-RK3399 開發板中對應的路徑為: /dev/spidev0.0
spidev對應的驅動程式碼: kernel/drivers/spi/spidev.c
核心config需要選上SPI_SPIDEV:
│ Symbol: SPI_SPIDEV [=y]
│ Type : tristate
│ Prompt: User mode SPI device driver support
│ Location:
│ -> Device Drivers
│ -> SPI support (SPI [=y])
│ Defined at drivers/spi/Kconfig:684
│ Depends on: SPI [=y] && SPI_MASTER [=y]
DTS配置如下:
&spi1 {
status = "okay";
max-freq = <48000000>;
[email protected] {
compatible = "linux,spidev";
reg = <0x00>;
spi-max-frequency = <48000000>;
};
};
FAQs
Q1: SPI資料傳送異常
A1: 確保 SPI 4個引腳的 IOMUX 配置正確, 確認 TX 送資料時,TX 引腳有正常的波形,CLK 頻率正確,CS 訊號有拉低,mode 與裝置匹配。
程式清單:
/*
* Driver for pwm demo on Firefly board.
*
* Copyright (C) 2016, Zhongshan T-chip Intelligent Technology Co.,ltd.
* Copyright 2006 Sam Chan
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define DEBUG
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spidev.h>
#define FIREFLY_SPI_READ_ID_CMD 0x9F
#define FIREFLY_SPI_PRINT_ID(rbuf) \
do { \
if (status == 0) \
dev_dbg(&spi->dev, "%s: ID = %02x %02x %02x %02x %02x\n", __FUNCTION__, \
rbuf[0], rbuf[1], rbuf[2], rbuf[3], rbuf[4]); \
else \
dev_err(&spi->dev, "%s: read ID error\n", __FUNCTION__); \
}while(0)
static int firefly_spi_read_w25x_id_0(struct spi_device *spi)
{
int status;
char tbuf[]={FIREFLY_SPI_READ_ID_CMD};
char rbuf[5];
struct spi_transfer t = {
.tx_buf = tbuf,
.len = sizeof(tbuf),
};
struct spi_transfer r = {
.rx_buf = rbuf,
.len = sizeof(rbuf),
};
struct spi_message m;
spi_message_init(&m);
spi_message_add_tail(&t, &m);
spi_message_add_tail(&r, &m);
status = spi_sync(spi, &m);
FIREFLY_SPI_PRINT_ID(rbuf);
return status;
}
static int firefly_spi_read_w25x_id_1(struct spi_device *spi)
{
int status;
char tbuf[] = {FIREFLY_SPI_READ_ID_CMD};
char rbuf[5];
status = spi_write_then_read(spi, tbuf, sizeof(tbuf), rbuf, sizeof(rbuf));
FIREFLY_SPI_PRINT_ID(rbuf);
return status;
}
static int firefly_spi_probe(struct spi_device *spi)
{
int ret = 0;
struct device_node __maybe_unused *np = spi->dev.of_node;
dev_dbg(&spi->dev, "Firefly SPI demo program\n");
if(!spi)
return -ENOMEM;
dev_dbg(&spi->dev, "firefly_spi_probe: setup mode %d, %s%s%s%s%u bits/w, %u Hz max\n",
(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
(spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
(spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
(spi->mode & SPI_3WIRE) ? "3wire, " : "",
(spi->mode & SPI_LOOP) ? "loopback, " : "",
spi->bits_per_word, spi->max_speed_hz);
firefly_spi_read_w25x_id_0(spi);
firefly_spi_read_w25x_id_1(spi);
return ret;
}
static struct of_device_id firefly_match_table[] = {
{ .compatible = "firefly,rk3399-spi",},
{},
};
static struct spi_driver firefly_spi_driver = {
.driver = {
.name = "firefly-spi",
.owner = THIS_MODULE,
.of_match_table = firefly_match_table,
},
.probe = firefly_spi_probe,
};
static int firefly_spi_init(void)
{
return spi_register_driver(&firefly_spi_driver);
}
module_init(firefly_spi_init);
static void firefly_spi_exit(void)
{
spi_unregister_driver(&firefly_spi_driver);
}
module_exit(firefly_spi_exit);
MODULE_AUTHOR("zhansb <[email protected]>");
MODULE_DESCRIPTION("Firefly SPI demo driver");
MODULE_ALIAS("platform:firefly-spi");
MODULE_LICENSE("GPL");
看一下讀寫函式吧:
static int firefly_spi_read_w25x_id_0(struct spi_device *spi)
{
int status;
char tbuf[]={FIREFLY_SPI_READ_ID_CMD};
char rbuf[5];
struct spi_transfer t = {
.tx_buf = tbuf,
.len = sizeof(tbuf),
};
struct spi_transfer r = {
.rx_buf = rbuf,
.len = sizeof(rbuf),
};
struct spi_message m;
spi_message_init(&m);
spi_message_add_tail(&t, &m);
spi_message_add_tail(&r, &m);
status = spi_sync(spi, &m);
FIREFLY_SPI_PRINT_ID(rbuf);
return status;
}
是不是和IIC的很像,來做一下對比:
static int read_reg(const struct i2c_client *client, unsigned int *buf , unsigned char address)
{
struct i2c_msg msg[2];
int ret;
unsigned char date1[2];
msg[0].addr = client->addr;
msg[0].buf = &address;
msg[0].len = 1;
msg[0].flags = 0;
msg[1].addr = client->addr;
msg[1].buf = date1;
msg[1].len = 2;
msg[1].flags = I2C_M_RD;
ret = i2c_transfer(client->adapter, msg, 2);
if (ret > 0)
{
printk(KERN_INFO "date1 : %d date1 :%d\n",date1[0],date1[1]);
*buf = (date1[0] << 8) | (date1[1]);
return 1;
}
else
return -EIO;
}
spi的總體框架從大體上應該和iic差不多吧,以後分析瞭如果說的不對,再來修改