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Fix a race condition in as3525 I2C driver caused by stacked ISRs.

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It was possible for interrupts of higher priority than the current IRQ
level to attempt to restart the interface while it was still active on
a transfer. The list modification also wasn't protected within the I2C
ISR itself.

Change-Id: I70635c307a1443bba6801c588cf1efde299db9a4
This commit is contained in:
Michael Sevakis 2015-02-14 15:18:52 -05:00
parent 98a69ec500
commit 36480c259f
1 changed files with 25 additions and 17 deletions
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42
firmware/target/arm/as3525/ascodec-as3525.c
View file

@ -159,21 +159,12 @@ static void ascodec_finish_req(struct ascodec_request *req)
*/
while (i2c_busy());
/* disable clock */
bitclr32(&CGU_PERI, CGU_I2C_AUDIO_MASTER_CLOCK_ENABLE);
req->status = 1;
if (req->callback) {
req->callback(req->data, req_data_ptr - req->data);
}
semaphore_release(&req->complete);
req_head = req->next;
req->next = NULL;
if (req_head == NULL)
req_tail = NULL;
}
static int ascodec_continue_req(struct ascodec_request *req, int irq_status)
@ -226,13 +217,12 @@ static void ascodec_start_req(struct ascodec_request *req)
void INT_I2C_AUDIO(void)
{
struct ascodec_request *req = req_head;
int irq_status = I2C2_MIS;
int status = REQ_FINISHED;
int status = ascodec_continue_req(req, irq_status);
if (req_head != NULL)
status = ascodec_continue_req(req_head, irq_status);
I2C2_INT_CLR |= irq_status; /* clear interrupt status */
I2C2_INT_CLR = irq_status; /* clear interrupt status */
if (status != REQ_UNFINISHED) {
/* mask rx/tx interrupts */
@ -240,16 +230,32 @@ void INT_I2C_AUDIO(void)
I2C2_IRQ_RXOVER|I2C2_IRQ_ACKTIMEO);
if (status == REQ_FINISHED)
ascodec_finish_req(req_head);
ascodec_finish_req(req);
int oldlevel = disable_irq_save(); /* IRQs are stacked */
/*
* If status == REQ_RETRY, this will restart
* the request because we didn't remove it from
* the request list
*/
if (req_head)
if (status == REQ_FINISHED) {
req_head = req->next;
req->next = NULL;
}
if (req_head == NULL) {
req_tail = NULL;
/* disable clock */
bitclr32(&CGU_PERI, CGU_I2C_AUDIO_MASTER_CLOCK_ENABLE);
} else {
ascodec_start_req(req_head);
}
restore_irq(oldlevel);
}
}
void i2c_init(void)
@ -278,7 +284,7 @@ void ascodec_init(void)
I2C2_CNTRL = I2C2_CNTRL_DEFAULT;
I2C2_IMR = 0x00; /* disable interrupts */
I2C2_INT_CLR |= I2C2_RIS; /* clear interrupt status */
I2C2_INT_CLR = I2C2_RIS; /* clear interrupt status */
VIC_INT_ENABLE = INTERRUPT_I2C_AUDIO;
VIC_INT_ENABLE = INTERRUPT_AUDIO;
@ -338,6 +344,8 @@ static void ascodec_submit(struct ascodec_request *req)
static void ascodec_wait(struct ascodec_request *req)
{
/* NOTE: Only safe from thread context */
if (irq_enabled()) {
semaphore_wait(&req->complete, TIMEOUT_BLOCK);
return;