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spi flash的频率配置 代码流程及最终的频率值。
基于4.14.55 内核,
\drivers\spi\spi-dw-fmsh.c (控制器)
\drivers\spi\spi-dw.c
\drivers\mtd\devices\m25p80.c (设备)
\drivers\spi\spi.c
- spi0: spi@e0001000 {
- compatible = "fmsh,dw-apb-ssi","snps,dw-apb-ssi";
- #address-cells = <1>;
- #size-cells = <0>;
- reg = <0xe0001000 0x1000>;
- interrupts = <GIC_SPI 22 IRQ_TYPE_LEVEL_HIGH>;
- num-cs = <3>;
- clocks = <&clkc NCLK_SPI0>, <&clkc NCLK_APB_SPI0>;
- clock-names = "clk_ref", "pclk";
- reg-io-width = <4>;
- spi-max-frequency = <1000000>;
- cs-gpios = <&portb 10 0>;
- status = "disabled";
-
-
- flash1@0 {
- compatible = "spi-flash","spansion,s25fl256s1", "jedec,spi-nor";
- reg = <0>;
- spi-max-frequency = <500000>;
- };
-
- spidev@1 {
- compatible = "spidev";
- spi-max-frequency = <20000000>;
- reg = <1>;
- };
- };
属性 | 说明 |
cs-gpios | 片选的配置。对于zync,其可能采用MIO或者EMIO,在设计时,vivado里面就配置好管脚 |
很多设备的套路都是先初始化控制器,然后再扫描控制器下的设备,对设备进行初始化。
初始化包括对硬件的初始化,以及根据硬件及DTS等配置初始化相关结构体,最终构成软件操作依赖。
控制器的初始化比较简单,只要明了驱动,进入probe就可以。
-
- static int dw_spi_fmsh_probe(struct platform_device *pdev)
- {
- struct dw_spi_mmio *dwsmmio;
- struct dw_spi *dws;
- struct resource *mem;
- int ret;
-
-
- dws->bus_num = pdev->id;
- //读取控制的输入频率,例如166M HZ
- dws->max_freq = clk_get_rate(dwsmmio->clk);
-
-
-
-
- ret = dw_spi_add_host(&pdev->dev, dws);
- if (ret)
- goto fail;
- printk("xiehj end: dw_spi_fmsh_probe\n");
- platform_set_drvdata(pdev, dwsmmio);
- return 0;
-
- fail:
- clk_disable_unprepare(dwsmmio->pclk);
- fail_pclk:
- clk_disable_unprepare(dwsmmio->clk);
-
- return ret;
- }
如下将其配置为master,SPI 通信分为master 、slave。
-
- int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
- {
- struct spi_master *master;
- int ret;
-
-
-
- ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED, dev_name(dev),
- master);
- if (ret < 0) {
- dev_err(dev, "can not get IRQ\n");
- goto err_free_master;
- }
- // 注册操作接口,这些操作接口在设备初始化时可能会回调,
-
- master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
- master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
- master->bus_num = dws->bus_num;
- master->num_chipselect = dws->num_cs;
- master->setup = dw_spi_setup;
- master->cleanup = dw_spi_cleanup;
- master->set_cs = dw_spi_set_cs;
- master->transfer_one = dw_spi_transfer_one;
- master->handle_err = dw_spi_handle_err;
- master->max_speed_hz = dws->max_freq; //master是控制器设备,设置为166M
- master->dev.of_node = dev->of_node;
- master->flags = SPI_MASTER_GPIO_SS;
-
-
- }
将控制器添加到设备后,后续芯片初始化时,命令的发送如何知道走整个控制器的相关接口的呢?此为通用的注册流程,即在下面的接口后,会进一步扫描DTS中的设备子节点,进而建立关联,此处非本文重点,感兴趣的自行阅读代码。套路都一样的。
ret = devm_spi_register_master(dev, master);
-
- int spi_register_controller(struct spi_controller *ctlr)
- {
- struct device *dev = ctlr->dev.parent;
- struct boardinfo *bi;
- int status = -ENODEV;
- int id, first_dynamic;
-
-
- .......................省去一堆
-
- /* add statistics */
- spin_lock_init(&ctlr->statistics.lock);
-
- mutex_lock(&board_lock);
- list_add_tail(&ctlr->list, &spi_controller_list);
- list_for_each_entry(bi, &board_list, list)
- spi_match_controller_to_boardinfo(ctlr, &bi->board_info);
- mutex_unlock(&board_lock);
-
- /* Register devices from the device tree and ACPI */
- 这里注册SPI下挂的设备
- of_register_spi_devices(ctlr);
- acpi_register_spi_devices(ctlr);
- done:
- return status;
- }
获取设备树里面配置
- static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
- struct device_node *nc)
- {
- u32 value;
- int rc;
-
- /* Mode (clock phase/polarity/etc.) */
-
-
- /* Device speed */
- rc = of_property_read_u32(nc, "spi-max-frequency", &value);
- if (rc) {
- dev_err(&ctlr->dev,
- "%pOF has no valid 'spi-max-frequency' property (%d)\n", nc, rc);
- return rc;
- }
- //注意这里从DTS读出的值,翻到了spi_device中,也就是FLASH等端点设备中,也就是端点设备需要的速率。
- spi->max_speed_hz = value;
-
- return 0;
- }
所谓的设备添加,即将控制器下面的设备添加到系统中,以便匹配后续的驱动。
在此流程中,如果设备最大频率没有配置,则采用控制器的最大频率
-
- int spi_setup(struct spi_device *spi)
- {
- //如下判断是否需要采用控制器的最大频率
- if (!spi->max_speed_hz)
- spi->max_speed_hz = spi->controller->max_speed_hz;
-
- if (spi->controller->setup)
- status = spi->controller->setup(spi);
-
- spi_set_cs(spi, false);
-
- dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\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,
- status);
-
- return status;
- }
设备添加到系统后,就调用驱动
-
- /*
- * board specific setup should have ensured the SPI clock used here
- * matches what the READ command supports, at least until this driver
- * understands FAST_READ (for clocks over 25 MHz).
- */
- static int m25p_probe(struct spi_device *spi)
- {
- struct flash_platform_data *data;
- struct m25p *flash;
- struct spi_nor *nor;
-
-
- nor = &flash->spi_nor;
-
- /* install the hooks */
- nor->read = m25p80_read;
- nor->write = m25p80_write;
- nor->write_reg = m25p80_write_reg;
- nor->read_reg = m25p80_read_reg;
-
- nor->dev = &spi->dev;
- spi_nor_set_flash_node(nor, spi->dev.of_node);
- nor->priv = flash;
-
- spi_set_drvdata(spi, flash);
- flash->spi = spi;
-
- if (spi->mode & SPI_RX_QUAD) {
- hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
-
- if (spi->mode & SPI_TX_QUAD)
- hwcaps.mask |= (SNOR_HWCAPS_READ_1_4_4 |
- SNOR_HWCAPS_PP_1_1_4 |
- SNOR_HWCAPS_PP_1_4_4);
- } else if (spi->mode & SPI_RX_DUAL) {
- hwcaps.mask |= SNOR_HWCAPS_READ_1_1_2;
-
- if (spi->mode & SPI_TX_DUAL)
- hwcaps.mask |= SNOR_HWCAPS_READ_1_2_2;
- }
-
- if (data && data->name)
- nor->mtd.name = data->name;
-
- /* For some (historical?) reason many platforms provide two different
- * names in flash_platform_data: "name" and "type". Quite often name is
- * set to "m25p80" and then "type" provides a real chip name.
- * If that's the case, respect "type" and ignore a "name".
- */
- if (data && data->type)
- flash_name = data->type;
- else if (!strcmp(spi->modalias, "spi-nor"))
- flash_name = NULL; /* auto-detect */
- else
- flash_name = spi->modalias;
- ret = spi_nor_scan(nor, flash_name, &hwcaps);
- if (ret)
- return ret;
- return mtd_device_register(&nor->mtd, data ? data->parts : NULL,
- data ? data->nr_parts : 0);
- }
提供:
1) flash 的读写接口,及寄存器读写接口。在通用的nor驱动里面回调这些接口。通用nor驱动主要对nor 命令进行封装。
2) 扫描设备。在设备驱动中扫描设备逻辑存在问题。在控制器中扫描更合适。
3) 将设备注册为MTD设备。
这里只要兼容,jedec,spi-nor 都会进到这个驱动中。
- static const struct of_device_id m25p_of_table[] = {
- /*
- * Generic compatibility for SPI NOR that can be identified by the
- * JEDEC READ ID opcode (0x9F). Use this, if possible.
- */
- { .compatible = "jedec,spi-nor" },
- {}
- };
SPI的频率设置在每次transfer时都会进行,因而需要关注此流程。从下面代码我们了解到
进行分频系数的设置,但是涉及到transfer->speed-hz
- static inline void spi_set_clk(struct dw_spi *dws, u16 div)
- {
- dw_writel(dws, DW_SPI_BAUDR, div);
- }
-
-
- static int dw_spi_transfer_one(struct spi_master *master,
- struct spi_device *spi, struct spi_transfer *transfer)
- {
- struct dw_spi *dws = spi_master_get_devdata(master);
- struct chip_data *chip = spi_get_ctldata(spi);
- u8 imask = 0;
- u16 txlevel = 0;
- u32 cr0;
- int ret;
-
- //在发送的时候,设置波特率的分频,每次都单打设置。
-
-
- /* Handle per transfer options for bpw and speed */
- if (transfer->speed_hz != dws->current_freq) {
- if (transfer->speed_hz != chip->speed_hz) {
- /* clk_div doesn't support odd number */
- chip->clk_div = (DIV_ROUND_UP(dws->max_freq, transfer->speed_hz) + 1) & 0xfffe;
- chip->speed_hz = transfer->speed_hz;
- }
- dws->current_freq = transfer->speed_hz;
- spi_set_clk(dws, chip->clk_div);
- }
-
-
- if (chip->poll_mode)
- return poll_transfer(dws);
- return 1;
- }
\drivers\spi\spi.c
__spi_sync ---》 status = __spi_validate(spi, message);
-
- static int __spi_validate(struct spi_device *spi, struct spi_message *message)
- {
- struct spi_controller *ctlr = spi->controller;
- struct spi_transfer *xfer;
- int w_size;
-
-
-
- if (!xfer->speed_hz)
- xfer->speed_hz = spi->max_speed_hz; //首先将xfer的频率设置为设备请求的最大频率
- if (!xfer->speed_hz)
- xfer->speed_hz = ctlr->max_speed_hz; //如果没有则设置控制器的最大频率
-
- if (ctlr->max_speed_hz && xfer->speed_hz > ctlr->max_speed_hz)
- xfer->speed_hz = ctlr->max_speed_hz;
-
- if (__spi_validate_bits_per_word(ctlr, xfer->bits_per_word))
- return -EINVAL;
-
- /*
- * SPI transfer length should be multiple of SPI word size
- * where SPI word size should be power-of-two multiple
- */
- if (xfer->bits_per_word <= 8)
- w_size = 1;
- else if (xfer->bits_per_word <= 16)
- w_size = 2;
- else
- w_size = 4;
-
- /* No partial transfers accepted */
- if (xfer->len % w_size)
- return -EINVAL;
-
- if (xfer->speed_hz && ctlr->min_speed_hz &&
- xfer->speed_hz < ctlr->min_speed_hz)
- return -EINVAL;
-
- if (xfer->tx_buf && !xfer->tx_nbits)
- xfer->tx_nbits = SPI_NBITS_SINGLE;
- if (xfer->rx_buf && !xfer->rx_nbits)
- xfer->rx_nbits = SPI_NBITS_SINGLE;
- /* check transfer tx/rx_nbits:
- * 1. check the value matches one of single, dual and quad
- * 2. check tx/rx_nbits match the mode in spi_device
- */
- if (xfer->tx_buf) {
- if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
- xfer->tx_nbits != SPI_NBITS_DUAL &&
- xfer->tx_nbits != SPI_NBITS_QUAD)
- return -EINVAL;
- if ((xfer->tx_nbits == SPI_NBITS_DUAL) &&
- !(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD)))
- return -EINVAL;
- if ((xfer->tx_nbits == SPI_NBITS_QUAD) &&
- !(spi->mode & SPI_TX_QUAD))
- return -EINVAL;
- }
- /* check transfer rx_nbits */
- if (xfer->rx_buf) {
- if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
- xfer->rx_nbits != SPI_NBITS_DUAL &&
- xfer->rx_nbits != SPI_NBITS_QUAD)
- return -EINVAL;
- if ((xfer->rx_nbits == SPI_NBITS_DUAL) &&
- !(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD)))
- return -EINVAL;
- if ((xfer->rx_nbits == SPI_NBITS_QUAD) &&
- !(spi->mode & SPI_RX_QUAD))
- return -EINVAL;
- }
- }
-
- message->status = -EINPROGRESS;
-
- return 0;
- }
1) 控制器的时钟配置
2) DTS 中设备 频率字段的配置
在spi dw中,实际工作的频率计算公式为:
chip->clk_div = (DIV_ROUND_UP(dws->max_freq, transfer->speed_hz) + 1) & 0xfffe;
chip->speed_hz = transfer->speed_hz;
此处计算分频值,计算
DIV_ROUND_UP(A,B) = int( (A+B-1)/B ),
例如,max_freq =166M, speed_hz配置为20M
则clk_div =(166.7+20-1)/20 +1= 9.285+1= 10也就是分频系数是10,此时设备期望的最大工作频率是20Mhz,实际工作为16.66MHZ=166.6/10
比如25M (166.7+24)/25=8.6 =8; 实际工作频率 166.7/8= 20.83Mhz
spi 信号在没有操作时,连时钟都没有输出,或者是由于这个流程。
读取ID 失败
m25p80 spi2.0: unrecognized JEDEC id bytes: 00, 00, 00
偶尔能读出一次。
经分析,由于 spi控制器与设备间经过逻辑转换,导致CS信号没有到设备侧导致。
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