usb: chipidea: fix RT issue for udc

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Signed-off-by Jeaho Hwang <[email protected]>

---
 drivers/usb/chipidea/udc.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

drivers/usb/chipidea/udc.c +0 -0

index 5f35cdd2cf1d..a90498f17cc4 100644

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Signed-off-by Jeaho Hwang <[email protected]>

---
 drivers/usb/chipidea/udc.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

drivers/usb/chipidea/udc.c +17 -4

index 5f35cdd2cf1d..a90498f17cc4 100644
@@ -102,6 +102,9 @@ static int hw_ep_flush(struct ci_hdrc *ci, int num, int dir)
 {
 	int n = hw_ep_bit(num, dir);
 
+    /* From zynq-7000 TRM, It can take a long time
+     * so irq disable is not a good option for RT
+     */
 	do {
 		/* flush any pending transfer */
 		hw_write(ci, OP_ENDPTFLUSH, ~0, BIT(n));

@@ -190,22 +193,32 @@ static int hw_ep_get_halt(struct ci_hdrc *ci, int num, int dir)
 static int hw_ep_prime(struct ci_hdrc *ci, int num, int dir, int is_ctrl)
 {
 	int n = hw_ep_bit(num, dir);
+	unsigned long flags;
+	int ret = 0;
 
 	/* Synchronize before ep prime */
 	wmb();
 
-	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
-		return -EAGAIN;
+	/* irq affects this routine so irq should be disabled on RT.
+	 * on standard kernel, irq is already disabled by callers.
+	 */
+	local_irq_save(flags);
+	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num))) {
+		ret = -EAGAIN;
+	goto out;
+	}
 
 	hw_write(ci, OP_ENDPTPRIME, ~0, BIT(n));
 
 	while (hw_read(ci, OP_ENDPTPRIME, BIT(n)))
 		cpu_relax();
 	if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
-		return -EAGAIN;
+		ret = -EAGAIN;
 
+out:
+	local_irq_restore(flags);
 	/* status shoult be tested according with manual but it doesn't work */
-	return 0;
+	return ret;
 }
 
 /**

Signature · 1 line

2.25.1

Quoted 5 lines · Jeaho Hwang

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Greg, do you have any suggestions about it, the RT kernel schedules the interrupt handler (top-half) out which causes the USB hardware atomic sequences are broken, these hardware operations needs to be executed within limited time.

Quoted 7 lines · Jeaho Hwang

Quoted 5 lines

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Quoted 3 lines

Greg, do you have any suggestions about it, the RT kernel schedules the interrupt handler (top-half) out which causes the USB hardware atomic sequences are broken, these hardware operations needs to be executed within limited time.

The RT kernel does its scheduling based on priorities. If the interrupt handler is scheduled out, it's because some other process with a higher priority needs to run. The answer should be to increase the handler's priority.

Alan Stern

Quoted 5 lines · Jeaho Hwang

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Greg, do you have any suggestions about it, the RT kernel schedules the interrupt handler (top-half) out which causes the USB hardware atomic sequences are broken, these hardware operations needs to be executed within limited time.

Quoted 4 lines · Jeaho Hwang

Quoted 3 lines

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

Quoted 6 lines

Quoted 2 lines

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Greg, do you have any suggestions about it, the RT kernel schedules the interrupt handler (top-half) out which causes the USB hardware atomic sequences are broken, these hardware operations needs to be executed within limited time.

Try working with the RT developers on this.

2021년 8월 16일 (월) 오후 2:22, Greg Kroah-Hartman <[email protected]>님이 작성:

Quoted 9 lines · Peter Chen

Quoted 7 lines · Jeaho Hwang

Quoted 5 lines

hw_ep_prime sometimes fails if irq occurs while it rus on RT kernel. to prevent local_irq_save should keep the function from irqs.

I am not sure where is the best to submit this patch, between RT and USB community so sending to both. thanks.

Quoted 5 lines

Quoted 3 lines

Greg, do you have any suggestions about it, the RT kernel schedules the interrupt handler (top-half) out which causes the USB hardware atomic sequences are broken, these hardware operations needs to be executed within limited time.

Try working with the RT developers on this.

Then do you think those kinds of patches should be applied to linux-rt instead of mainline?