From 8126651009315ed0d71aa44ba403b1a91e511fe6 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Wed, 25 Dec 2019 18:48:38 +0100
Subject: [PATCH 1/2] cpu/lpc2387: timer: implement timer_set()

We can achieve greater accuracy for the relative timer_set()
if we don't use the generic implementation.

Use the same approach as used by atmega_common to trigger interrupts
for too small offsets.

tests/periph_timer_short_relative_set should now succeed for all intervals.
---
 cpu/lpc23xx/include/periph_cpu.h |  5 +++++
 cpu/lpc23xx/periph/timer.c       | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/cpu/lpc23xx/include/periph_cpu.h b/cpu/lpc23xx/include/periph_cpu.h
index b70270ca73..d29ba35c31 100644
--- a/cpu/lpc23xx/include/periph_cpu.h
+++ b/cpu/lpc23xx/include/periph_cpu.h
@@ -128,6 +128,11 @@ typedef struct {
  */
 #define TIMER_CHANNEL_NUMOF (4U)
 
+/**
+ * @brief   Prevent shared timer functions from being used
+ */
+#define PERIPH_TIMER_PROVIDES_SET
+
 /**
  * @brief   Declare needed generic SPI functions
  * @{
diff --git a/cpu/lpc23xx/periph/timer.c b/cpu/lpc23xx/periph/timer.c
index f1d3e20a40..3cda55753b 100644
--- a/cpu/lpc23xx/periph/timer.c
+++ b/cpu/lpc23xx/periph/timer.c
@@ -21,6 +21,7 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "irq.h"
 #include "periph_conf.h"
 #include "periph_cpu.h"
 #include "periph/timer.h"
@@ -167,6 +168,37 @@ int timer_set_absolute(tim_t tim, int channel, unsigned int value)
     dev->MR[channel] = value;
     /* Match Interrupt */
     dev->MCR |= (1 << (channel * 3));
+
+    return 0;
+}
+
+int timer_set(tim_t tim, int channel, unsigned int timeout)
+{
+    if (((unsigned) tim >= TIMER_NUMOF) || ((unsigned) channel >= TIMER_CHANNEL_NUMOF)) {
+        return -1;
+    }
+
+    /* Interrupt will only be generated on increment,
+       so a 0 timeout is not possible */
+    if (timeout == 0) {
+        timeout = 1;
+    }
+
+    lpc23xx_timer_t *dev = get_dev(tim);
+
+    unsigned state = irq_disable();
+    dev->TCR = 0;
+
+    unsigned absolute = timeout + dev->TC;
+    unsigned mask = 1 << (channel * 3);
+
+    dev->MR[channel] = absolute;
+    dev->MCR |= mask;
+    set_oneshot(tim, channel);
+
+    dev->TCR = 1;
+    irq_restore(state);
+
     return 0;
 }
 

From 178167621b706e150463cb8a6bbb1e094d90704b Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@googlemail.com>
Date: Fri, 14 Aug 2020 14:48:15 +0200
Subject: [PATCH 2/2] cpu/lpc2387: timer: use bitarithm_test_and_clear()

---
 cpu/lpc23xx/periph/timer.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/cpu/lpc23xx/periph/timer.c b/cpu/lpc23xx/periph/timer.c
index 3cda55753b..750f551e23 100644
--- a/cpu/lpc23xx/periph/timer.c
+++ b/cpu/lpc23xx/periph/timer.c
@@ -258,13 +258,6 @@ void timer_stop(tim_t tim)
 
 static inline void chan_handler(lpc23xx_timer_t *dev, unsigned tim_num, unsigned chan_num)
 {
-    const uint32_t mask = (1 << chan_num);
-
-    if ((dev->IR & mask) == 0) {
-        return;
-    }
-
-    dev->IR |= mask;
     if (is_oneshot(tim_num, chan_num)) {
         dev->MCR &= ~(1 << (chan_num * 3));
     }
@@ -274,8 +267,15 @@ static inline void chan_handler(lpc23xx_timer_t *dev, unsigned tim_num, unsigned
 
 static inline void isr_handler(lpc23xx_timer_t *dev, int tim_num)
 {
-    for (unsigned i = 0; i < TIMER_CHANNEL_NUMOF; ++i) {
-        chan_handler(dev, tim_num, i);
+    uint32_t state = dev->IR;
+    uint8_t chan = 0;
+
+    /* clear interrupt flags */
+    dev->IR = state;
+
+    while (state) {
+        state = bitarithm_test_and_clear(state, &chan);
+        chan_handler(dev, tim_num, chan);
     }
 
     /* we must not forget to acknowledge the handling of the interrupt */