linux: Adapt servo0 channels for beagleboard kernel 4.14.108-ti (#2746)

The beagleboard TI kernel 4.14 and 4.19 contain a commit which change
the device names ("pwm: Create device class for pwm channels") from
pwmN to pwm-${chip}:N. This commit was never merged into the upstream
kernel.

Decrease the number of pwm channels to a more reasonable 16. Increase
the number of pwm chips to 8 since the replicape servo pwm outputs are
on pwmchip4.

Update replicape code to detect appropriate channel.

Signed-off-by: Janne Grunau <janne-gh@jannau.net>

1 files changed, 29 insertions, 12 deletions

diff --git a/src/linux/hard_pwm.c b/src/linux/hard_pwm.c
index 25bfb2e7..f14b844b 100644
--- a/src/linux/hard_pwm.c
+++ b/src/linux/hard_pwm.c
@@ -10,6 +10,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <errno.h> // errno, ENOENT
 
 #include "gpio.h" // struct gpio_pwm
 #include "internal.h" // NSECS_PER_TICK
@@ -20,16 +21,21 @@
 DECL_CONSTANT("PWM_MAX", MAX_PWM);
 
 #define HARD_PWM_START (1<<16)
-#define HARD_PWM(chip, pin) (((chip)<<8) + (pin) + HARD_PWM_START)
-#define HARD_PWM_TO_CHIP(hard_pwm) (((hard_pwm) - HARD_PWM_START) >> 8)
-#define HARD_PWM_TO_PIN(hard_pwm)  (((hard_pwm) - HARD_PWM_START) & 0xff)
+#define HARD_PWM(chip, pin) (((chip)<<4) + (pin) + HARD_PWM_START)
+#define HARD_PWM_TO_CHIP(hard_pwm) (((hard_pwm) - HARD_PWM_START) >> 4)
+#define HARD_PWM_TO_PIN(hard_pwm)  (((hard_pwm) - HARD_PWM_START) & 0xf)
 
-DECL_ENUMERATION_RANGE("pin", "pwmchip0/pwm0", HARD_PWM(0, 0), 256);
-DECL_ENUMERATION_RANGE("pin", "pwmchip1/pwm0", HARD_PWM(1, 0), 256);
-DECL_ENUMERATION_RANGE("pin", "pwmchip2/pwm0", HARD_PWM(2, 0), 256);
-DECL_ENUMERATION_RANGE("pin", "pwmchip3/pwm0", HARD_PWM(3, 0), 256);
+DECL_ENUMERATION_RANGE("pin", "pwmchip0/pwm0", HARD_PWM(0, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip1/pwm0", HARD_PWM(1, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip2/pwm0", HARD_PWM(2, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip3/pwm0", HARD_PWM(3, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip4/pwm0", HARD_PWM(4, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip5/pwm0", HARD_PWM(5, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip6/pwm0", HARD_PWM(6, 0), 16);
+DECL_ENUMERATION_RANGE("pin", "pwmchip7/pwm0", HARD_PWM(7, 0), 16);
 
 #define PWM_PATH "/sys/class/pwm/pwmchip%u/pwm%u/%s"
+#define PWM_PATH_BB "/sys/class/pwm/pwm-%u:%u/%s"
 
 struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint16_t val)
 {
@@ -37,15 +43,26 @@ struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint16_t val)
     char scratch[16];
     uint8_t chip_id = HARD_PWM_TO_CHIP(pin);
     uint8_t pwm_id = HARD_PWM_TO_PIN(pin);
+    const char * pwm_path = PWM_PATH;
 
     struct gpio_pwm g = {};
     g.period = cycle_time * NSECS_PER_TICK;
 
     // configure period/cycle time. Always in nanoseconds
-    snprintf(filename, sizeof(filename), PWM_PATH, chip_id, pwm_id, "period");
+    snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id, "period");
     int fd = open(filename, O_WRONLY|O_CLOEXEC);
-    if (fd == -1) {
-        report_errno("pwm period", fd);
+    if (fd == -1 && errno == ENOENT) {
+        // upstream pwm control file does not exists try BeagleBoard scheme
+        pwm_path = PWM_PATH_BB;
+        snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id,
+                 "period");
+        fd = open(filename, O_WRONLY|O_CLOEXEC);
+        if (fd == -1) {
+            report_errno("pwm " PWM_PATH_BB "period for pin", pin);
+            goto fail;
+        }
+    } else if (fd == -1) {
+        report_errno("pwm " PWM_PATH "period for pin", pin);
         goto fail;
     }
     snprintf(scratch, sizeof(scratch), "%u", cycle_time * NSECS_PER_TICK);
@@ -53,7 +70,7 @@ struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint16_t val)
     close(fd);
 
     // write duty cycle
-    snprintf(filename, sizeof(filename), PWM_PATH, chip_id, pwm_id,
+    snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id,
              "duty_cycle");
     fd = open(filename, O_WRONLY|O_CLOEXEC);
     if (fd == -1) {
@@ -65,7 +82,7 @@ struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint16_t val)
     gpio_pwm_write(g, val);
 
     // enable PWM
-    snprintf(filename, sizeof(filename), PWM_PATH, chip_id, pwm_id, "enable");
+    snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id, "enable");
     fd = open(filename, O_WRONLY|O_CLOEXEC);
     if (fd == -1) {
         close(g.fd);