Re: [PATCH v2] usb: dwc3: gadget: Wait for end transfer complete before free irq

From: Felipe Balbi
Date: Thu Oct 13 2016 - 06:57:55 EST



Hi,

Felipe Balbi <balbi@xxxxxxxxxx> writes:
> Hi,
>
> Baolin Wang <baolin.wang@xxxxxxxxxx> writes:
>>>>> I'm thinking this is a bug in configfs interface of Gadget API, not
>>>>> dwc3. The only reason for this to happen would be if we get to
>>>>> ->udc_stop() with endpoints still enabled.
>>>>>
>>>>> Can you check if that's the case? i.e. can you check if any endpoints
>>>>> are still enabled when we get here?
>>>>
>>>> No, it is not any endpoints are still enabled. Like I said in commit
>>>> message, we will start end transfer command when disable the endpoint,
>>>> if the end transfer command complete event comes after we have freed
>>>> the gadget irq, it will trigger the interrupt line all the time to
>>>> crash the system.
>>>
>>> I see what the problem is. Databook tells us we *must* set CMDIOC when
>>> issuing EndTransfer command and we should always wait for Command
>>> Complete IRQ. However, we took a shortcut and just delayed for 100us
>>> after issuing End Transfer.
>>
>> Yes, but 100us delay is not enough in some scenarios, like changing
>> function with configfs frequently, we will met problems.
>
> heh, 100us *is* enough. However we still get an IRQ because we requested
> for it. If you want to fix this, then you need to find a way to get rid
> of that 100us udelay() and add a proper wait_for_completion() to delay
> execution until command complete IRQ fires up.

I haven't tested this yet, but it shows the idea (I think we might still
have a race with ep_queue if we're still waiting for End Transfer, but
that's easy to sort out by checking for DWC3_EP_END_TRANSFER_PENDING
before calling kick_transfer). Could you have a look and, perhaps, run a
test?

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index e878366ead00..24a77e9f9bba 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -26,6 +26,7 @@
#include <linux/dma-mapping.h>
#include <linux/mm.h>
#include <linux/debugfs.h>
+#include <linux/wait.h>

#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
@@ -504,6 +505,7 @@ struct dwc3_event_buffer {
* @endpoint: usb endpoint
* @pending_list: list of pending requests for this endpoint
* @started_list: list of started requests on this endpoint
+ * @wait_end_transfer: wait_queue_head_t for waiting on End Transfer complete
* @lock: spinlock for endpoint request queue traversal
* @regs: pointer to first endpoint register
* @trb_pool: array of transaction buffers
@@ -529,6 +531,8 @@ struct dwc3_ep {
struct list_head pending_list;
struct list_head started_list;

+ wait_queue_head_t wait_end_transfer;
+
spinlock_t lock;
void __iomem *regs;

@@ -545,7 +549,7 @@ struct dwc3_ep {
#define DWC3_EP_BUSY (1 << 4)
#define DWC3_EP_PENDING_REQUEST (1 << 5)
#define DWC3_EP_MISSED_ISOC (1 << 6)
-
+#define DWC3_EP_END_TRANSFER_PENDING (1 << 7)
/* This last one is specific to EP0 */
#define DWC3_EP0_DIR_IN (1 << 31)

@@ -1047,6 +1051,9 @@ struct dwc3_event_depevt {
#define DEPEVT_TRANSFER_BUS_EXPIRY 2

u32 parameters:16;
+
+/* For Command Complete Events */
+#define DEPEVT_PARAMETER_CMD(n) (((n) & (0xf << 24)) >> 24)
} __packed;

/**
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 3ba05b12e49a..8037bff43485 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -598,6 +598,8 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep,
reg |= DWC3_DALEPENA_EP(dep->number);
dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);

+ init_waitqueue_head(&dep->wait_end_transfer);
+
if (usb_endpoint_xfer_control(desc))
return 0;

@@ -2156,6 +2158,7 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
{
struct dwc3_ep *dep;
u8 epnum = event->endpoint_number;
+ u8 cmd;

dep = dwc->eps[epnum];

@@ -2200,8 +2203,13 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
return;
}
break;
- case DWC3_DEPEVT_RXTXFIFOEVT:
case DWC3_DEPEVT_EPCMDCMPLT:
+ cmd = DEPEVT_PARAMETER_CMD(event->parameters);
+
+ if (cmd == DWC3_DEPCMD_ENDTRANSFER)
+ dep->flags &= ~DWC3_EP_END_TRANSFER_PENDING;
+ break;
+ case DWC3_DEPEVT_RXTXFIFOEVT:
break;
}
}
@@ -2246,6 +2254,7 @@ static void dwc3_reset_gadget(struct dwc3 *dwc)
}

static void dwc3_stop_active_transfer(struct dwc3 *dwc, u32 epnum, bool force)
+__releases(&dwc->lock) __acquires(&dwc->lock)
{
struct dwc3_ep *dep;
struct dwc3_gadget_ep_cmd_params params;
@@ -2295,6 +2304,12 @@ static void dwc3_stop_active_transfer(struct dwc3 *dwc, u32 epnum, bool force)
memset(&params, 0, sizeof(params));
ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
WARN_ON_ONCE(ret);
+
+ dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
+ wait_event_cmd(dep->wait_end_transfer,
+ !(dep->flags & DWC3_EP_END_TRANSFER_PENDING),
+ spin_unlock_irq(&dwc->lock), spin_lock_irq(&dwc->lock));
+
dep->resource_index = 0;
dep->flags &= ~DWC3_EP_BUSY;




--
balbi

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