本文主要是介绍AM335x GPMC使用总结，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
AM335X GPMC使用比较灵活，可以配置为
● 8-bit 同步或者异步并行总线 (非burst)
● 16-bit 同步或者异步并行中线
● 16-bit 非复用的NORFlash
● 16-bit 数据和地址总线复用的NORFlash
● 8-bit 和 16-bitNAND Flash
● 16-bit pSRAM.
下面以EVB335X扩展EXAR ST16C554为例，讲解如何配置GPMC。
1. 配置GPMC引脚
static structpinmux_config gpmc_pin_mux[] = {
/********* 8-bit data bus **************/
{"gpmc_ad0.gpmc_ad0", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad1.gpmc_ad1", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad2.gpmc_ad2", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad3.gpmc_ad3", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad4.gpmc_ad4", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad5.gpmc_ad5", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad6.gpmc_ad6", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
{"gpmc_ad7.gpmc_ad7", OMAP_MUX_MODE0 | AM33XX_PIN_INPUT_PULLUP},
/**************** 8-bit address bus ****************/
{"gpmc_a0.gpmc_a0", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a1.gpmc_a1", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a2.gpmc_a2", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a3.gpmc_a3", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a4.gpmc_a4", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a5.gpmc_a5", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a6.gpmc_a6", OMAP_MUX_MODE0| AM33XX_PIN_OUTPUT},
{"gpmc_a7.gpmc_a7", OMAP_MUX_MODE0 |AM33XX_PIN_OUTPUT},
{"gpmc_csn2.gpmc_csn2", OMAP_MUX_MODE0 | AM33XX_PULL_DISA},
{"gpmc_oen_ren.gpmc_oen_ren", OMAP_MUX_MODE0 | AM33XX_PULL_DISA},
{"gpmc_wen.gpmc_wen", OMAP_MUX_MODE0 | AM33XX_PULL_DISA},
{NULL, 0},
};
setup_pin_mux(gpmc_pin_mux);
2. 申请GPMC内存
unsigned long serial_gpmc_mem_base_phys;
int cs = 2; /*EVB335X评估板中ST16C554接在CS2上 */
gpmc_cs_request(cs, SZ_16M, &serial_gpmc_mem_base_phys)
此时serial_gpmc_mem_base_phys存放的是该CS上多对应的物理起始地址。
3. 设置GMPC类型
gpmc_cs_configure(cs, GPMC_CONFIG_DEV_TYPE, GPMC_DEVICETYPE_NOR);/*设置为并行总线*/
val = GPMC_CONFIG1_READTYPE_SYNC; /* 设置为8-bit sync */
val |= GPMC_CONFIG1_WRITETYPE_SYNC;
gpmc_cs_write_reg(cs, GPMC_CS_CONFIG1, val);
4. 设置GPMC时序
因此时序设置为: (单位ns)
static structgpmc_timings ext_uart_timings = {
/* Minimum clock period for synchronous mode (in picoseconds)*/
.sync_clk = 0,
/* CS signal timings corresponding to GPMC_CONFIG2 */
.cs_on = 10, /*T6s */
.cs_rd_off = 80, /*oe_off + T7h */
.cs_wr_off = 60, /*Tcs for write: we_off + T13h */
/* ADV signal timings corresponding to GPMC_CONFIG3 */
// .adv_on = 0, /* Address setup Tas*/
// .adv_rd_off = 110, /* Read deassertion time Trd + Tdd*/
// .adv_wr_off = 90, /* Write deassertion time Twr + Tdh*/
/* WE signals timings corresponding to GPMC_CONFIG4 */
.we_on = 20, /*WE assertion time: cs_on + T13d */
.we_off = 60, /*WE deassertion time: we_on + T13w */
/* OE signals timings corresponding to GPMC_CONFIG4 */
.oe_on = 20, /*OE assertion time: cs_on + T7d */
.oe_off = 70, /*OE deassertion time: oe_on + T7w */
/* Access time and cycle time timings corresponding toGPMC_CONFIG5 */
// .page_burst_access = 2 * 10, /* Multiple access word delay */
.access = 60, /*Start-cycle to first data valid delay: at leaset oe_on + T12d */
.rd_cycle = 110, /*Total read cycle time: cs_rd_off + (T9d - T7h) - oe_on */
.wr_cycle = 90, /*Total write cycle time: cs_wr_off + (T15d - T13h) - we_on */
/* The following are only on OMAP3430 */
.wr_access = 40, /*WRACCESSTIME: max we_off - T16s */
.wr_data_mux_bus = 0, /*WRDATAONADMUXBUS */
};
gpmc_cs_set_timings(cs,&ext_uart_timings)
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