Better detection of concurrent ADC access.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@3197 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/cpu/arm/drv/adc_at91.c b/bertos/cpu/arm/drv/adc_at91.c
index bb6a8d11ffd1409fe86d557a86d31e6d233714f1..faa0d1817f4379a3964daa2d8173c011a7d16f45 100644 (file)
--- a/bertos/cpu/arm/drv/adc_at91.c
+++ b/bertos/cpu/arm/drv/adc_at91.c
@@ -126,13 +126,13 @@ void adc_hw_select_ch(uint8_t ch)
 /**
  * Start an ADC convertion.
  * If a kernel is present, preempt until convertion is complete, otherwise
- * a busy wait on ADCS bit is done.
+ * a busy wait on ADC_DRDY bit is done.
  */
 uint16_t adc_hw_read(void)
 {
-       ASSERT(!(ADC_SR & ADC_EOC_MASK));
-
        #if CONFIG_KERN
+               /* Ensure ADC is not already in use by another process */
+               ASSERT(adc_process == NULL);
                adc_process = proc_current();
        #endif
 
@@ -143,13 +143,19 @@ uint16_t adc_hw_read(void)
                // Ensure IRQs enabled.
                IRQ_ASSERT_ENABLED();
                sig_wait(SIG_ADC_COMPLETE);
+
+               /* Prevent race condition in case of preemptive kernel */
+               uint16_t ret = ADC_LCDR;
+               MEMORY_BARRIER;
+               adc_process = NULL;
+               return ret;
        #else
                //Wait in polling until is done
                while (!(ADC_SR & BV(ADC_DRDY)));
-       #endif
 
-       //Return the last converted data
-       return(ADC_LCDR);
+               //Return the last converted data
+               return(ADC_LCDR);
+       #endif
 }
 
 /**