pru: Add support for ADC input

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/pru/Kconfig

@@ -2,6 +2,11 @@
 
 if MACH_PRU
 
+config PRU_SELECT
+    bool
+    default y
+    select HAVE_GPIO_ADC
+
 config BOARD_DIRECTORY
     string
     default "pru"

src/pru/gpio.c

@@ -4,9 +4,11 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
+#include "board/io.h" // readl
 #include "command.h" // shutdown
 #include "compiler.h" // ARRAY_SIZE
 #include "gpio.h" // gpio_out_setup
+#include "internal.h" // ADC
 #include "sched.h" // sched_shutdown
 
 
@@ -140,3 +142,68 @@ gpio_in_read(struct gpio_in g)
 {
     return !!(*g.reg & g.bit);
 }
+
+
+/****************************************************************
+ * Analog to Digital Converter (ADC) pins
+ ****************************************************************/
+
+DECL_CONSTANT(ADC_MAX, 4095);
+
+struct gpio_adc
+gpio_adc_setup(uint8_t pin)
+{
+    uint8_t chan = pin - ARRAY_SIZE(digital_regs) * 32;
+    if (chan >= 8)
+        shutdown("Not an adc channel");
+    if (!readl(&ADC->ctrl))
+        shutdown("ADC module not enabled");
+    return (struct gpio_adc){ .chan = chan };
+}
+
+enum { ADC_DUMMY=0xff };
+static uint8_t last_analog_read = ADC_DUMMY;
+static uint16_t last_analog_sample;
+
+// Try to sample a value. Returns zero if sample ready, otherwise
+// returns the number of clock ticks the caller should wait before
+// retrying this function.
+uint32_t
+gpio_adc_sample(struct gpio_adc g)
+{
+    uint8_t last = last_analog_read;
+    if (last == ADC_DUMMY) {
+        // Start sample
+        last_analog_read = g.chan;
+        writel(&ADC->stepenable, 1 << (g.chan + 1));
+        goto need_delay;
+    }
+    if (last == g.chan) {
+        // Check if sample ready
+        while (readl(&ADC->fifo0count)) {
+            uint32_t sample = readl(&ADC->fifo0data);
+            if (sample >> 16 == g.chan) {
+                last_analog_read = ADC_DUMMY;
+                last_analog_sample = sample;
+                return 0;
+            }
+        }
+    }
+need_delay:
+    return 160;
+}
+
+// Read a value; use only after gpio_adc_sample() returns zero
+uint16_t
+gpio_adc_read(struct gpio_adc g)
+{
+    return last_analog_sample;
+}
+
+// Cancel a sample that may have been started with gpio_adc_sample()
+void
+gpio_adc_cancel_sample(struct gpio_adc g)
+{
+    if (last_analog_read == g.chan)
+        last_analog_read = ADC_DUMMY;
+}

src/pru/gpio.h

@@ -19,4 +19,12 @@ struct gpio_in {
 struct gpio_in gpio_in_setup(uint8_t pin, int8_t pull_up);
 uint8_t gpio_in_read(struct gpio_in g);
 
+struct gpio_adc {
+    uint8_t chan;
+};
+struct gpio_adc gpio_adc_setup(uint8_t pin);
+uint32_t gpio_adc_sample(struct gpio_adc g);
+uint16_t gpio_adc_read(struct gpio_adc g);
+void gpio_adc_cancel_sample(struct gpio_adc g);
+
 #endif // gpio.h

src/pru/internal.h

@@ -34,6 +34,37 @@ struct shared_mem {
 #define SIGNAL_PRU0_WAITING 0xefefefef
 #define SIGNAL_PRU1_READY   0xabababab
 
-static struct shared_mem *SHARED_MEM = (void*)0x10000;
+#define SHARED_MEM ((struct shared_mem *)0x10000)
+
+// Hardware ADC registers
+struct beaglebone_adc {
+    uint32_t pad_00[10];
+    uint32_t irqstatus;
+    uint32_t irqenable_set;
+    uint32_t irqenable_clr;
+    uint32_t irqwakeup;
+    uint32_t dmaenable_set;
+    uint32_t dmaenable_clr;
+    uint32_t ctrl;
+    uint32_t adcstat;
+    uint32_t adcrange;
+    uint32_t adc_clkdiv;
+    uint32_t adc_misc;
+    uint32_t stepenable;
+    uint32_t idleconfig;
+    uint32_t ts_charge_stepconfig;
+    uint32_t ts_charge_delay;
+    struct {
+        uint32_t config;
+        uint32_t delay;
+    } step[16];
+    uint32_t fifo0count;
+    uint32_t pad_e8[6];
+    uint32_t fifo0data;
+    uint32_t pad_104[63];
+    uint32_t fifo1data;
+};
+
+#define ADC ((struct beaglebone_adc *)0x44e0d000)
 
 #endif // internal.h

src/pru/main.c

@@ -90,8 +90,6 @@ static void
 timer_init(void)
 {
     CT_IEP.TMR_CNT = 0;
-    CT_IEP.TMR_CMP_CFG = 0x01 << 1;
-    CT_IEP.TMR_GLB_CFG = 0x11;
     timer_shutdown();
 }
 

src/pru/pru0.c

@@ -8,6 +8,7 @@
 #include <string.h> // memset
 #include <pru/io.h> // write_r31
 #include <pru_cfg.h> // CT_CFG
+#include <pru_iep.h> // CT_IEP
 #include <pru_intc.h> // CT_INTC
 #include <pru_rpmsg.h> // pru_rpmsg_send
 #include <pru_virtio_ids.h> // VIRTIO_ID_RPMSG
@@ -76,6 +77,44 @@ process_io(struct pru_rpmsg_transport *transport)
 }
 
 
+/****************************************************************
+ * Peripheral reset
+ ****************************************************************/
+
+static void
+timer_reset(void)
+{
+    CT_IEP.TMR_CMP_CFG = 0x01 << 1;
+    CT_IEP.TMR_GLB_CFG = 0x11;
+}
+
+static void
+adc_reset(void)
+{
+    // Disable ADC
+    ADC->ctrl = (1<<2);
+    barrier();
+    // Clear registers
+    ADC->irqstatus = 0xffffffff;
+    ADC->irqenable_clr = 0xffffffff;
+    ADC->dmaenable_clr = 0xffffffff;
+    ADC->adc_clkdiv = 0;
+    ADC->stepenable = 0;
+    ADC->idleconfig = 0;
+    int i;
+    for (i=0; i<8; i++) {
+        ADC->step[i].config = i<<19;
+        ADC->step[i].delay = 0;
+    }
+    // Enable ADC
+    barrier();
+    writel(&ADC->ctrl, 0x07);
+    // Drain fifo
+    while (readl(&ADC->fifo0count))
+        readl(&ADC->fifo0data);
+}
+
+
 /****************************************************************
  * Resource table
  ****************************************************************/
@@ -218,8 +257,12 @@ main(void)
                              , CHAN_DESC, CHAN_PORT) != PRU_RPMSG_SUCCESS)
         ;
 
-    // Wait for PRU1 to be ready
+    // Reset peripherals
     memset(SHARED_MEM, 0, sizeof(*SHARED_MEM));
+    timer_reset();
+    adc_reset();
+
+    // Wait for PRU1 to be ready
     writel(&SHARED_MEM->signal, SIGNAL_PRU0_WAITING);
     while (readl(&SHARED_MEM->signal) != SIGNAL_PRU1_READY)
         ;