From ac8123d2da74ac0bb6cb2d968bf79fe48905ad87 Mon Sep 17 00:00:00 2001
From: barthess <barthess@35acf78f-673a-0410-8e92-d51de3d6d3f4>
Date: Wed, 7 Dec 2011 14:13:57 +0000
Subject: I2C. Added note about different API classes usage.
git-svn-id: svn://svn.code.sf.net/p/chibios/svn/branches/i2c_dev@3569 35acf78f-673a-0410-8e92-d51de3d6d3f4
---
os/hal/platforms/STM32/i2c_lld.c | 47 ++++++++++++++++++++++++++++++++--------
1 file changed, 38 insertions(+), 9 deletions(-)
(limited to 'os')
diff --git a/os/hal/platforms/STM32/i2c_lld.c b/os/hal/platforms/STM32/i2c_lld.c
index d843591e1..f3291f819 100644
--- a/os/hal/platforms/STM32/i2c_lld.c
+++ b/os/hal/platforms/STM32/i2c_lld.c
@@ -43,6 +43,30 @@
* Otherwise there is a risk of setting a second STOP, START or PEC request.
*/
+/*===========================================================================*/
+/* Knowledge base. */
+/*===========================================================================*/
+/*
+Not all system functions are usable in a given context.
+
+The most restrictive type are the i-class, an I-class function is a function that must:
+- Not access the "current" thread in any way (from an ISR the current thread
+is random so it is meaningless).
+- Not reschedule internally (from an ISR the reschedule is done at the end of
+the ISR chain, rescheduling from within an ISR is forbidden because would
+leave the IRQ stack not empty with all kind of funny consequences.
+- Not try to change state for the current thread.
+- Must be invoked between a lock() and an unlock() but never lock/unlock internally.
+
+A bit less restrictive are the S-class that must simply:
+- Be invoked between a lock() and an unlock() but never lock/unlock internally.
+S-class can reschedule internally, access the current thread implicitly and
+also change state so are not eligible for ISR context.
+
+Normal functions can be invoked from thread context only but have no internal
+restrictions.
+*/
+
/*===========================================================================*/
/* Driver local definitions. */
/*===========================================================================*/
@@ -155,12 +179,12 @@ static void i2c_serve_event_interrupt(I2CDriver *i2cp) {
/* catch BTF event after the end of trasmission */
if (i2cp->rxbytes > 1){
/* start "read after write" operation */
- i2c_lld_master_receive(i2cp, (i2cp->slave_addr >> 1), i2cp->rxbuf, i2cp->rxbytes);
+ i2c_lld_master_receive(i2cp, (i2cp->slave_addr >> 1),
+ i2cp->rxbuf, i2cp->rxbytes);
return;
}
else
i2cp->id_i2c->CR1 |= I2C_CR1_STOP;
- // FIXME: change this polling to something else
while(i2cp->id_i2c->CR1 & I2C_CR1_STOP)
;
_i2c_isr_code(i2cp, i2cp->id_slave_config);
@@ -181,7 +205,6 @@ static void i2c_lld_serve_rx_end_irq(I2CDriver *i2cp){
dmaStreamDisable(i2cp->dmarx);
i2cp->id_i2c->CR1 |= I2C_CR1_STOP;
- // FIXME: change this polling to something else
while(i2cp->id_i2c->CR1 & I2C_CR1_STOP)
;
_i2c_isr_code(i2cp, i2cp->id_slave_config);
@@ -209,10 +232,10 @@ static void i2c_serve_error_interrupt(I2CDriver *i2cp) {
chSysLockFromIsr();
/* clear interrupt falgs just to be safe */
- dmaStreamClearInterrupt(i2cp->dmatx);
- dmaStreamClearInterrupt(i2cp->dmarx);
dmaStreamDisable(i2cp->dmatx);
dmaStreamDisable(i2cp->dmarx);
+ dmaStreamClearInterrupt(i2cp->dmatx);
+ dmaStreamClearInterrupt(i2cp->dmarx);
chSysUnlockFromIsr();
reg = i2cp->id_i2c;
@@ -344,13 +367,13 @@ void i2c_lld_init(void) {
#endif /* STM32_I2C_USE_I2C3 */
}
-
/**
* @brief Configures and activates the I2C peripheral.
*
* @param[in] i2cp pointer to the @p I2CDriver object
*/
void i2c_lld_start(I2CDriver *i2cp) {
+
i2cp->dmamode = STM32_DMA_CR_DMEIE | STM32_DMA_CR_TEIE;
if (i2cp->id_state == I2C_STOP) { /* If in stopped state then enables the I2C clock.*/
@@ -641,15 +664,21 @@ void i2c_lld_set_opmode(I2CDriver *i2cp) {
}
-
-
/**
* @brief Deactivates the I2C peripheral.
*
* @param[in] i2cp pointer to the @p I2CDriver object
*/
void i2c_lld_stop(I2CDriver *i2cp) {
- if (i2cp->id_state == I2C_READY) { /* If in ready state then disables the I2C clock.*/
+
+ if (i2cp->id_state != I2C_STOP) { /* If in ready state then disables the I2C clock.*/
+
+ dmaStreamDisable(i2cp->dmatx);
+ dmaStreamDisable(i2cp->dmarx);
+ dmaStreamClearInterrupt(i2cp->dmatx);
+ dmaStreamClearInterrupt(i2cp->dmarx);
+ dmaStreamRelease(i2cp->dmatx);
+ dmaStreamRelease(i2cp->dmarx);
#if STM32_I2C_USE_I2C1
if (&I2CD1 == i2cp) {
--
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