转自:http://blog.csdn.net/hustyangju/article/details/21165721
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S3C6410 SPI全双工读写流程分析
一、SPI控制器datasheet
1详细请参考:http://blog.csdn.net/hustyangju/article/details/20474659
2 SPI的所有寄存器都是映射到内核空间的,采用基地址+偏移地址的方式访问
static volatile void __iomem *spiregs; //global variable for mapping spiregister
spiregs = (volatile)ioremap(0x7F00B000,0x30); //just request for the spi0
3 下文可能用到的偏移地址
[cpp] view plain copy
- #define S3C_CH_CFG (0x00) //SPI configuration
- #define S3C_CLK_CFG (0x04) //Clock configuration
- #define S3C_MODE_CFG (0x08) //SPI FIFO control
- #define S3C_SLAVE_SEL (0x0C) //Slave selection
- #define S3C_SPI_INT_EN (0x10) //SPI interrupt enable
- #define S3C_SPI_STATUS (0x14) //SPI status
- #define S3C_SPI_TX_DATA (0x18) //SPI TX data
- #define S3C_SPI_RX_DATA (0x1C) //SPI RX data
- #define S3C_PACKET_CNT (0x20) //count how many data master gets
- #define S3C_PENDING_CLR (0x24) //Pending clear
- #define S3C_SWAP_CFG (0x28) //SWAPconfig register
- #define S3C_FB_CLK (0x28) //SWAP FB config register
- #define SPI_CH_SW_RST (1<<5)
- #define SPI_CH_MASTER (0<<4)
- #define SPI_CH_SLAVE (1<<4)
- #define SPI_CH_RISING (0<<3)
- #define SPI_CH_FALLING (1<<3)
- #define SPI_CH_FORMAT_A (0<<2)
- #define SPI_CH_FORMAT_B (1<<2)
- #define SPI_CH_RXCH_OFF (0<<1)
- #define SPI_CH_RXCH_ON (1<<1)
- #define SPI_CH_TXCH_OFF (0<<0)
- #define SPI_CH_TXCH_ON (1<<0)
- #define SPI_CLKSEL_PCLK (0<<9)
- #define SPI_CLKSEL_USBCLK (1<<9)
- #define SPI_CLKSEL_ECLK (2<<9)
- #define SPI_ENCLK_DISABLE (0<<8)
- #define SPI_ENCLK_ENABLE (1<<8)
- #define SPI_MODE_CH_TSZ_BYTE (0<<29)
- #define SPI_MODE_CH_TSZ_HALFWORD (1<<29)
- #define SPI_MODE_CH_TSZ_WORD (2<<29)
- #define SPI_MODE_BUS_TSZ_BYTE (0<<17)
- #define SPI_MODE_BUS_TSZ_HALFWORD (1<<17)
- #define SPI_MODE_BUS_TSZ_WORD (2<<17)
- #define SPI_MODE_RXDMA_OFF (0<<2)
- #define SPI_MODE_RXDMA_ON (1<<2)
- #define SPI_MODE_TXDMA_OFF (0<<1)
- #define SPI_MODE_TXDMA_ON (1<<1)
- #define SPI_MODE_SINGLE (0<<0)
- #define SPI_MODE_4BURST (1<<0)
- #define SPI_SLAVE_MAN (0<<1)
- #define SPI_SLAVE_AUTO (1<<1)
- #define SPI_SLAVE_SIG_ACT (0<<0)
- #define SPI_SLAVE_SIG_INACT (1<<0)
- #define SPI_INT_TRAILING_DIS (0<<6)
- #define SPI_INT_TRAILING_EN (1<<6)
- #define SPI_INT_RX_OVERRUN_DIS (0<<5)
- #define SPI_INT_RX_OVERRUN_EN (1<<5)
- #define SPI_INT_RX_UNDERRUN_DIS (0<<4)
- #define SPI_INT_RX_UNDERRUN_EN (1<<4)
- #define SPI_INT_TX_OVERRUN_DIS (0<<3)
- #define SPI_INT_TX_OVERRUN_EN (1<<3)
- #define SPI_INT_TX_UNDERRUN_DIS (0<<2)
- #define SPI_INT_TX_UNDERRUN_EN (1<<2)
- #define SPI_INT_RX_FIFORDY_DIS (0<<1)
- #define SPI_INT_RX_FIFORDY_EN (1<<1)
- #define SPI_INT_TX_FIFORDY_DIS (0<<0)
- #define SPI_INT_TX_FIFORDY_EN (1<<0)
- #define SPI_STUS_TX_DONE (1<<21)
- #define SPI_STUS_TRAILCNT_ZERO (1<<20)
- #define SPI_STUS_RX_OVERRUN_ERR (1<<5)
- #define SPI_STUS_RX_UNDERRUN_ERR (1<<4)
- #define SPI_STUS_TX_OVERRUN_ERR (1<<3)
- #define SPI_STUS_TX_UNDERRUN_ERR (1<<2)
- #define SPI_STUS_RX_FIFORDY (1<<1)
- #define SPI_STUS_TX_FIFORDY (1<<0)
- #define SPI_PACKET_CNT_DIS (0<<16)
- #define SPI_PACKET_CNT_EN (1<<16)
二、重点参数及初始化步骤
1 双通道SPI管脚配置
2 传输模型配置
/* Set transfer type (CPOL & CPHA set) */
spi_chcfg= SPI_CH_RISING | SPI_CH_FORMAT_A;
spi_chcfg|= SPI_CH_MASTER;
writel(spi_chcfg , spiregs + S3C_CH_CFG);
详细请参考:http://blog.csdn.net/hustyangju/article/details/20474659
3 时钟配置
使用PCLK,外部时钟66M,100分屏:
/* Set clock configuration register
* SPIclockout = clock source / (2 * (prescaler +1))
* PCLK=66Mhz, SPI clockout = clock source /(2 * (prescaler +1)) */
spi_clkcfg= SPI_ENCLK_ENABLE;
spi_clkcfg|= SPI_CLKSEL_PCLK;
writel(spi_clkcfg , spiregs + S3C_CLK_CFG);
spi_clkcfg= readl( spiregs + S3C_CLK_CFG);
spi_clkcfg|= 49; // the least spi speed =660Khz
writel(spi_clkcfg , spiregs + S3C_CLK_CFG);
4 SPI 模块设置
/* Set SPI MODE configuration register */
spi_modecfg= SPI_MODE_CH_TSZ_BYTE| SPI_MODE_BUS_TSZ_BYTE;
spi_modecfg|= SPI_MODE_TXDMA_OFF| SPI_MODE_SINGLE| SPI_MODE_RXDMA_OFF;
spi_modecfg&= ~( 0x3f << 5);
spi_modecfg|= ( 0x1 << 5); // Tx FIFOtrigger level in INT mode
spi_modecfg&= ~( 0x3f << 11);
spi_modecfg|= ( 0x1 << 11); // Rx FIFOtrigger level in INT mode
spi_modecfg&= ~( 0x3ff << 19);
spi_modecfg|= ( 0x1 << 19); // Counting ofTailing Bytes
writel(spi_modecfg,spiregs + S3C_MODE_CFG);
设置在fifo和bus中的数据宽度为byte,关闭DMA访问fifo,并设置fifo中保存最大字节数为1,设置接收和发送fifo的触发值为1byte。
5 中断配置
/* SetSPI INT_EN register */
writel(spi_inten,spiregs + S3C_SPI_INT_EN); //u32 spi_inten =0x00
writel(0x1f,spiregs + S3C_PENDING_CLR);
6 设置最大接收数据包数量
SPI can control the number of packets to bereceived in master mode.
If there is any number of packets to bereceived, justset the SFR
(Packet_Count_reg). SPI stops generating SPICLK when the number
ofpackets is thesame as what you set. It is mandatory to
follow software orhardware reset before this function is
reloaded.(Software reset can clear allregisters except special function
registers, but hardware reset clears allregisters.)
这里使能并设置为最大值。
/* Set Packet Count configuration register */
spi_packet= SPI_PACKET_CNT_EN;
spi_packet|= 0xffff;
writel(spi_packet,spiregs + S3C_PACKET_CNT);
7 打开spi接收和发送通道
/* SetTx or Rx Channel on */
spi_chcfg= readl(spiregs + S3C_CH_CFG);
spi_chcfg|= SPI_CH_TXCH_OFF | SPI_CH_RXCH_OFF;
spi_chcfg|= SPI_CH_TXCH_ON;
spi_chcfg|= SPI_CH_RXCH_ON;
writel(spi_chcfg,spiregs + S3C_CH_CFG);
8 启动发送/接收和关闭送法/接收
通过置0和置1NSSOUT位来开启和关闭。
三 SPI全双工收发协议分析
1 全双工,就是TX和RX同时进行。
2 往哪里收?往哪里发?
datasheet上:CPU (or DMA) mustwrite data on the register SPI_TX_DATA,
to write data in FIFO. Data on theregister areautomatically moved to Tx
FIFOs. To read data from Rx FIFOs, CPU (orDMA) must access the
registerSPI_RX_DATA and then data are automatically
sentto the register SPI_RX_DATA.
所以,对于处在内核空间的驱动来说,发送数据是往SPI_TX_DATA寄存器里写数据,接收是往SPI_RX_DATA寄存器里读数据。当然没这么简单!!
3 SPI发数据流程分析
提醒一点:SPI支持全双工,注意外设是半双工还是全双工?
按照上文设置,我们每次发送和接收一个byte。
(1)置0 NSSOUT
(2)往SPI_TX_DATA寄存器写一个byte,byte数据会自动移入TX FIFO,因为(1)中已经选中了外设,所以SPI master会自动读取TX FIFO中的byte数据移入TX移位寄存器,并开始发往bus。
(3)也就是说,驱动只需要从内核空间往SPI_TX_DATA寄存器上写数据,就完成了SPI发数据的操作了。
(4)全双工,意味着,发数据的同时也要从SPI_RX_DATA寄存器中读一个byte数据。但是,有可能第一次读并不会真正读到数据,因为没有数据被接收到RX移位寄存器。所以忽略这次的读取数据。
(5)置1 NSSOUT
4 SPI接收数据流程分析
如果外设是单双工,考虑在读数据的时候对spi复位!因为如果读数据发生在写数据后面,数据已经在发数据时读取到RX FIFO中了,只需从SPI_RX_DATA中取出数据就行了。
(1)置0 NSSOUT
(2)因为全双工,在发送数据的同时,spi master会读取byte字节并移入RX
FIFO。所以从SPI_RX_DATA寄存器读取一个byte,byte数据会自动R从X
FIFO移入到SPI_RX_DATA寄存器。(3)也就是说,驱动只需要从内核空间往SPI_RX_DATA寄存器读取数据,就完成了SPI接收数据的操作了。
(4)全双工,意味着,接收数据的同时也要从SPI_TX_DATA寄存器中发送一个byte数据。但是,读数据的时候发送的数据可能不是真正想要发送的数据,因为有些外设不是全双工工作。
(5)置1 NSSOUT
5 SPI收发条件判断
这是SPI收发协议里最难的部分了。
SPI状态寄存器:
1 是否准备好发数据?
[cpp] view plain copy
- /* spi_wait_TX_ready()- wait for TX_READY and TX_DONE */
- static BOOL spi_wait_TX_ready( void)
- {
- unsignedlong loops = msecs_to_loops(10);
- u32val = 0;
- do{
- val= readl(spiregs + S3C_SPI_STATUS);
- }while(!((val & SPI_STUS_TX_DONE) && (val & SPI_STUS_TX_FIFORDY))&& loops--);
- if(loops == 0)
- returnFALSE;
- else
- returnTRUE;
- }
2 发数据是否完成?
[cpp] view plain copy
- /* spi_wait_TX_done()- wait for TX_DONE */
- static BOOL spi_wait_TX_done( void)
- {
- unsignedlong loops = msecs_to_loops(10);
- u32val = 0;
- do{
- val= readl(spiregs + S3C_SPI_STATUS);
- }while(!(val & SPI_STUS_TX_DONE) &&loops--);
- if(loops == 0)
- returnFALSE;
- else
- returnTRUE;
- }
3 是否准备好接收数据?
[cpp] view plain copy
- /* spi_wait_RX_ready()- wait for RX_READY */
- static BOOL spi_wait_RX_ready( void)
- {
- unsignedlong loops = msecs_to_loops(10);
- u32val = 0;
- do{
- val= readl(spiregs + S3C_SPI_STATUS);
- }while(!(val & SPI_STUS_TRAILCNT_ZERO) && loops--);
- if(loops == 0)
- returnFALSE;
- else
- returnTRUE;
- }
6 最终全双工SPI从半双工外设发送和接收数据函数
[cpp] view plain copy
- BOOL spi_sendbyte( BYTE data)
- {
- BYTEchr;
- u32spi_chcfg = spiregs + S3C_CH_CFG;
- if(!spi_wait_TX_ready())
- {
- printk("%s:failed to get tx channel.\n");
- returnFALSE;
- }
- writel(data, spiregs + S3C_SPI_TX_DATA);
- while(!spi_wait_RX_ready());
- readl(spiregs + S3C_SPI_RX_DATA);
- returnTRUE;
- }
- /* spi_flush_fifo()- Clear the TxFIFO , RxFIFO and TX/RX shift register
- * @spiregs: the SPI register address*/
- VOID spi_flush_fifo(void *spiregs)
- {
- /* soft rest the spi controller, flush theFIFO */
- if(spi_wait_TX_done())
- {
- writel(readl(spiregs+ S3C_CH_CFG) | SPI_CH_SW_RST, spiregs + S3C_CH_CFG);
- writel(readl(spiregs+ S3C_CH_CFG) & ~SPI_CH_SW_RST, spiregs + S3C_CH_CFG);
- }
- }
- /* spi_readbyte()- Read a byte received on SPI0 */
- BYTE spi_readbyte( void)
- {
- u32tmp;
- u32spi_chcfg = spiregs + S3C_CH_CFG;
- BYTEret;
- if(!spi_wait_TX_ready())
- returnFALSE;
- spi_flush_fifo(spiregs);
- writel(0xFF, spiregs + S3C_SPI_TX_DATA);
- if(spi_wait_RX_ready())
- {
- tmp= readl(spiregs + S3C_SPI_RX_DATA);
- ret= tmp & 0xff;
- }
- returnret;
- }
原文地址:https://www.cnblogs.com/sky-heaven/p/8269712.html