Date:   Mon, 21 Jan 2019 20:09:49 +0530
From:   Balakrishna Godavarthi <bgodavar@...eaurora.org>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [RFC,v2] Bluetooth: hci_qca: Collect controller memory dump
 during SSR

Hi Marcel,

On 2019-01-18 14:24, Marcel Holtmann wrote:
> Hi Balakrishna,
> 
>>>>>> We will collect the ramdump of BT controller when hardware error 
>>>>>> event
>>>>>> received before rebooting the HCI layer. Before restarting a 
>>>>>> subsystem
>>>>>> or a process running on a subsystem, it is often required to 
>>>>>> request
>>>>>> either a subsystem or a process to perform proper cache dump and
>>>>>> software failure reason into a memory buffer which application
>>>>>> processor can retrieve afterwards. SW developers can often provide
>>>>>> initial investigation by looking into that debugging information.
>>>>>> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
>>>>>> ---
>>>>>> changes v2:
>>>>>> * entirely an newer approach handling with an work queue.
>>>>>> ---
>>>>>> drivers/bluetooth/hci_qca.c | 289 
>>>>>> ++++++++++++++++++++++++++++++++++--
>>>>>> 1 file changed, 278 insertions(+), 11 deletions(-)
>>>>>> diff --git a/drivers/bluetooth/hci_qca.c 
>>>>>> b/drivers/bluetooth/hci_qca.c
>>>>>> index f036c8f98ea3..62b768bc32ec 100644
>>>>>> --- a/drivers/bluetooth/hci_qca.c
>>>>>> +++ b/drivers/bluetooth/hci_qca.c
>>>>>> @@ -32,6 +32,7 @@
>>>>>> #include <linux/clk.h>
>>>>>> #include <linux/debugfs.h>
>>>>>> #include <linux/delay.h>
>>>>>> +#include <linux/devcoredump.h>
>>>>>> #include <linux/device.h>
>>>>>> #include <linux/gpio/consumer.h>
>>>>>> #include <linux/mod_devicetable.h>
>>>>> don't we have some crashdump core facility that could be utilized 
>>>>> here?
>>>> [Bala]: no i don't think so. that is reason calling devcoredump.h
>>> what is wrong with using devcoredump.h?
>> 
>> [Bala]: using the  devcoredump.h
>> 
>>>>>> @@ -57,9 +58,10 @@
>>>>>> /* Controller states */
>>>>>> #define STATE_IN_BAND_SLEEP_ENABLED	1
>>>>>> -#define IBS_WAKE_RETRANS_TIMEOUT_MS	100
>>>>>> +#define	IBS_WAKE_RETRANS_TIMEOUT_MS	100
>>>>>> #define IBS_TX_IDLE_TIMEOUT_MS		2000
>>>>>> -#define BAUDRATE_SETTLE_TIMEOUT_MS	300
>>>>>> +#define	BAUDRATE_SETTLE_TIMEOUT_MS	300
>>>>>> +#define MEMDUMP_COLLECTION_TIMEOUT_MS	8000
>>>>>> /* susclk rate */
>>>>>> #define SUSCLK_RATE_32KHZ	32768
>>>>>> @@ -67,6 +69,13 @@
>>>>>> /* Controller debug log header */
>>>>>> #define QCA_DEBUG_HANDLE	0x2EDC
>>>>>> +/* Controller dump header */
>>>>>> +#define QCA_SSR_DUMP_HANDLE		0x0108
>>>>>> +#define QCA_DUMP_PACKET_SIZE		255
>>>>>> +#define QCA_LAST_SEQUENCE_NUM		0xFFFF
>>>>>> +#define QCA_CRASHBYTE_PACKET_LEN	1100
>>>>>> +#define QCA_MEMDUMP_BYTE		0xFB
>>>>>> +
>>>>>> /* HCI_IBS transmit side sleep protocol states */
>>>>>> enum tx_ibs_states {
>>>>>> 	HCI_IBS_TX_ASLEEP,
>>>>>> @@ -89,12 +98,41 @@ enum hci_ibs_clock_state_vote {
>>>>>> 	HCI_IBS_RX_VOTE_CLOCK_OFF,
>>>>>> };
>>>>>> +/* Controller memory dump states */
>>>>>> +enum qca_memdump_states {
>>>>>> +	QCA_MEMDUMP_IDLE,
>>>>>> +	QCA_MEMDUMP_COLLECTING,
>>>>>> +	QCA_MEMDUMP_COLLECTED,
>>>>>> +	QCA_MEMDUMP_TIMEOUT,
>>>>>> +};
>>>>>> +
>>>>>> +struct qca_memdump_data {
>>>>>> +	char *memdump_buf_head;
>>>>>> +	char *memdump_buf_tail;
>>>>>> +	u32 current_seq_no;
>>>>>> +	u32 received_dump;
>>>>>> +};
>>>>>> +
>>>>>> +struct qca_memdump_event_hdr {
>>>>>> +	__u8    evt;
>>>>>> +	__u8    plen;
>>>>>> +	__u16   opcode;
>>>>>> +	__u16   seq_no;
>>>>>> +	__u8    reserved;
>>>>>> +} __packed;
>>>>>> +
>>>>>> +
>>>>>> +struct qca_dump_size {
>>>>>> +	u32 dump_size;
>>>>>> +} __packed;
>>>>>> +
>>>>>> struct qca_data {
>>>>>> 	struct hci_uart *hu;
>>>>>> 	struct sk_buff *rx_skb;
>>>>>> 	struct sk_buff_head txq;
>>>>>> -	struct sk_buff_head tx_wait_q;	/* HCI_IBS wait queue	*/
>>>>>> -	spinlock_t hci_ibs_lock;	/* HCI_IBS state lock	*/
>>>>>> +	struct sk_buff_head tx_wait_q;		/* HCI_IBS wait queue	*/
>>>>>> +	struct sk_buff_head rx_memdump_q;	/* Memdump wait queue	*/
>>>>>> +	spinlock_t hci_ibs_lock;		/* HCI_IBS state lock	*/
>>>>>> 	u8 tx_ibs_state;	/* HCI_IBS transmit side power state*/
>>>>>> 	u8 rx_ibs_state;	/* HCI_IBS receive side power state */
>>>>>> 	bool tx_vote;		/* Clock must be on for TX */
>>>>>> @@ -103,12 +141,17 @@ struct qca_data {
>>>>>> 	u32 tx_idle_delay;
>>>>>> 	struct timer_list wake_retrans_timer;
>>>>>> 	u32 wake_retrans;
>>>>>> +	struct timer_list memdump_timer;
>>>>>> +	u32 memdump_delay;
>>>>>> 	struct workqueue_struct *workqueue;
>>>>>> 	struct work_struct ws_awake_rx;
>>>>>> 	struct work_struct ws_awake_device;
>>>>>> 	struct work_struct ws_rx_vote_off;
>>>>>> 	struct work_struct ws_tx_vote_off;
>>>>>> +	struct work_struct ctrl_memdump_evt;
>>>>>> +	struct qca_memdump_data *qca_memdump;
>>>>>> 	unsigned long flags;
>>>>>> +	enum qca_memdump_states memdump_state;
>>>>>> 	/* For debugging purpose */
>>>>>> 	u64 ibs_sent_wacks;
>>>>>> @@ -173,6 +216,7 @@ struct qca_serdev {
>>>>>> static int qca_power_setup(struct hci_uart *hu, bool on);
>>>>>> static void qca_power_shutdown(struct hci_uart *hu);
>>>>>> static int qca_power_off(struct hci_dev *hdev);
>>>>>> +static void qca_controller_memdump(struct work_struct *work);
>>>>>> static void __serial_clock_on(struct tty_struct *tty)
>>>>>> {
>>>>>> @@ -446,6 +490,21 @@ static void 
>>>>>> hci_ibs_wake_retrans_timeout(struct timer_list *t)
>>>>>> 		hci_uart_tx_wakeup(hu);
>>>>>> }
>>>>>> +static void hci_memdump_timeout(struct timer_list *t)
>>>>>> +{
>>>>>> +	struct qca_data *qca = from_timer(qca, t, tx_idle_timer);
>>>>>> +	struct hci_uart *hu = qca->hu;
>>>>>> +	struct qca_memdump_data *qca_memdump = qca->qca_memdump;
>>>>>> +	char *memdump_buf = qca_memdump->memdump_buf_tail;
>>>>>> +
>>>>>> +	bt_dev_err(hu->hdev, "clearing allocated memory due to memdump 
>>>>>> timeout");
>>>>>> +	kfree(memdump_buf);
>>>>>> +	kfree(qca_memdump);
>>>>>> +	qca->memdump_state = QCA_MEMDUMP_TIMEOUT;
>>>>>> +	del_timer(&qca->memdump_timer);
>>>>>> +	cancel_work_sync(&qca->ctrl_memdump_evt);
>>>>>> +}
>>>>>> +
>>>>>> /* Initialize protocol */
>>>>>> static int qca_open(struct hci_uart *hu)
>>>>>> {
>>>>>> @@ -461,6 +520,7 @@ static int qca_open(struct hci_uart *hu)
>>>>>> 	skb_queue_head_init(&qca->txq);
>>>>>> 	skb_queue_head_init(&qca->tx_wait_q);
>>>>>> +	skb_queue_head_init(&qca->rx_memdump_q);
>>>>>> 	spin_lock_init(&qca->hci_ibs_lock);
>>>>>> 	qca->workqueue = alloc_ordered_workqueue("qca_wq", 0);
>>>>>> 	if (!qca->workqueue) {
>>>>>> @@ -473,6 +533,7 @@ static int qca_open(struct hci_uart *hu)
>>>>>> 	INIT_WORK(&qca->ws_awake_device, qca_wq_awake_device);
>>>>>> 	INIT_WORK(&qca->ws_rx_vote_off, qca_wq_serial_rx_clock_vote_off);
>>>>>> 	INIT_WORK(&qca->ws_tx_vote_off, qca_wq_serial_tx_clock_vote_off);
>>>>>> +	INIT_WORK(&qca->ctrl_memdump_evt, qca_controller_memdump);
>>>>>> 	qca->hu = hu;
>>>>>> @@ -500,7 +561,7 @@ static int qca_open(struct hci_uart *hu)
>>>>>> 	qca->tx_votes_off = 0;
>>>>>> 	qca->rx_votes_on = 0;
>>>>>> 	qca->rx_votes_off = 0;
>>>>>> -
>>>>>> +	qca->memdump_state = QCA_MEMDUMP_IDLE;
>>>>>> 	hu->priv = qca;
>>>>>> 	if (hu->serdev) {
>>>>>> @@ -528,6 +589,9 @@ static int qca_open(struct hci_uart *hu)
>>>>>> 	timer_setup(&qca->tx_idle_timer, hci_ibs_tx_idle_timeout, 0);
>>>>>> 	qca->tx_idle_delay = IBS_TX_IDLE_TIMEOUT_MS;
>>>>>> +	timer_setup(&qca->memdump_timer, hci_memdump_timeout, 0);
>>>>>> +	qca->memdump_delay = MEMDUMP_COLLECTION_TIMEOUT_MS;
>>>>>> +
>>>>>> 	BT_DBG("HCI_UART_QCA open, tx_idle_delay=%u, wake_retrans=%u",
>>>>>> 	       qca->tx_idle_delay, qca->wake_retrans);
>>>>>> @@ -605,8 +669,10 @@ static int qca_close(struct hci_uart *hu)
>>>>>> 	skb_queue_purge(&qca->tx_wait_q);
>>>>>> 	skb_queue_purge(&qca->txq);
>>>>>> +	skb_queue_purge(&qca->rx_memdump_q);
>>>>>> 	del_timer(&qca->tx_idle_timer);
>>>>>> 	del_timer(&qca->wake_retrans_timer);
>>>>>> +	del_timer(&qca->memdump_timer);
>>>>>> 	destroy_workqueue(qca->workqueue);
>>>>>> 	qca->hu = NULL;
>>>>>> @@ -866,6 +932,141 @@ static int qca_recv_acl_data(struct hci_dev 
>>>>>> *hdev, struct sk_buff *skb)
>>>>>> 	return hci_recv_frame(hdev, skb);
>>>>>> }
>>>>>> +static void qca_controller_memdump(struct work_struct *work)
>>>>>> +{
>>>>>> +	struct qca_data *qca = container_of(work, struct qca_data,
>>>>>> +					    ctrl_memdump_evt);
>>>>>> +	struct hci_uart *hu = qca->hu;
>>>>>> +	struct sk_buff *skb;
>>>>>> +	struct qca_memdump_event_hdr *cmd_hdr;
>>>>>> +	struct qca_memdump_data *qca_memdump = qca->qca_memdump;
>>>>>> +	struct qca_dump_size *dump;
>>>>>> +	char *memdump_buf;
>>>>>> +	char nullBuff[QCA_DUMP_PACKET_SIZE] = { 0 };
>>>>>> +	u16 opcode, seq_no;
>>>>>> +	u32 dump_size;
>>>>>> +
>>>>>> +	while ((skb = skb_dequeue(&qca->rx_memdump_q))) {
>>>>>> +
>>>>>> +		if (!qca_memdump) {
>>>>>> +			qca_memdump = kzalloc(sizeof(struct qca_memdump_data),
>>>>>> +					      GFP_ATOMIC);
>>>>>> +			if (!qca_memdump)
>>>>>> +				return;
>>>>>> +
>>>>>> +			qca->qca_memdump = qca_memdump;
>>>>>> +		}
>>>>>> +
>>>>>> +		qca->memdump_state = QCA_MEMDUMP_COLLECTING;
>>>>>> +		cmd_hdr = (void *) skb->data;
>>>>>> +		opcode = __le16_to_cpu(cmd_hdr->opcode);
>>>>>> +		seq_no = __le16_to_cpu(cmd_hdr->seq_no);
>>>>>> +		skb_pull(skb, sizeof(struct qca_memdump_event_hdr));
>>>>>> +
>>>>>> +		if (!seq_no) {
>>>>>> +
>>>>>> +			/* This is the first frame of memdump packet from
>>>>>> +			 * the controller, Disable IBS to recevie dump
>>>>>> +			 * with out any interruption, ideally time required for
>>>>>> +			 * the controller to send the dump is 8 seconds. let us
>>>>>> +			 * start timer to handle this asynchronous activity.
>>>>>> +			 */
>>>>>> +			clear_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags);
>>>>>> +
>>>>>> +			dump = (void *) skb->data;
>>>>>> +			dump_size = __le32_to_cpu(dump->dump_size);
>>>>>> +			if (!(dump_size)) {
>>>>>> +				bt_dev_err(hu->hdev, "QCA invalid memdump size");
>>>>>> +				kfree_skb(skb);
>>>>>> +				return;
>>>>>> +			}
>>>>>> +
>>>>>> +			bt_dev_info(hu->hdev, "QCA: collecting memdump started"
>>>>>> +				     "of size:%u", dump_size);
>>>>>> +			mod_timer(&qca->memdump_timer, (jiffies +
>>>>>> +				  msecs_to_jiffies(qca->memdump_delay)));
>>>>>> +
>>>>>> +			skb_pull(skb, sizeof(dump_size));
>>>>>> +			memdump_buf = vmalloc(dump_size);
>>>>>> +			qca_memdump->memdump_buf_head = memdump_buf;
>>>>>> +			qca_memdump->memdump_buf_tail = memdump_buf;
>>>>>> +		}
>>>>>> +
>>>>>> +		memdump_buf = qca_memdump->memdump_buf_tail;
>>>>>> +
>>>>>> +		/* If sequence no 0 is missed then there is no point in
>>>>>> +		 * accepting the other sequences.
>>>>>> +		 */
>>>>>> +		if (!memdump_buf) {
>>>>>> +			bt_dev_err(hu->hdev, "QCA: Discarding other packets");
>>>>>> +			kfree(qca_memdump);
>>>>>> +			kfree_skb(skb);
>>>>>> +			qca->qca_memdump = NULL;
>>>>>> +			return;
>>>>>> +		}
>>>>>> +
>>>>>> +		/* There could be chance of missing some packets from
>>>>>> +		 * the controller. In such cases let us store the dummy
>>>>>> +		 * packets in the buffer.
>>>>>> +		 */
>>>>>> +		while ((seq_no > qca_memdump->current_seq_no + 1) &&
>>>>>> +			seq_no != QCA_LAST_SEQUENCE_NUM) {
>>>>>> +			bt_dev_err(hu->hdev, "QCA controller missed packet:%d",
>>>>>> +				   qca_memdump->current_seq_no);
>>>>>> +			memcpy(memdump_buf, nullBuff, QCA_DUMP_PACKET_SIZE);
>>>>>> +			memdump_buf = memdump_buf + QCA_DUMP_PACKET_SIZE;
>>>>>> +			qca_memdump->received_dump += QCA_DUMP_PACKET_SIZE;
>>>>>> +			qca_memdump->current_seq_no++;
>>>>>> +		}
>>>>>> +
>>>>>> +		memcpy(memdump_buf, (unsigned char *) skb->data, skb->len);
>>>>>> +		memdump_buf = memdump_buf + skb->len;
>>>>>> +		qca_memdump->memdump_buf_tail = memdump_buf;
>>>>>> +		qca_memdump->current_seq_no = seq_no + 1;
>>>>>> +		qca_memdump->received_dump += skb->len;
>>>>>> +		qca->qca_memdump = qca_memdump;
>>>>>> +		kfree_skb(skb);
>>>>>> +		if (seq_no == QCA_LAST_SEQUENCE_NUM) {
>>>>>> +			bt_dev_info(hu->hdev, "QCA writing crash dump of size %d 
>>>>>> bytes",
>>>>>> +				   qca_memdump->received_dump);
>>>>>> +			memdump_buf = qca_memdump->memdump_buf_head;
>>>>>> +			dev_coredumpv(&hu->serdev->dev, memdump_buf,
>>>>>> +				      qca_memdump->received_dump, GFP_KERNEL);
>>>>>> +			// Revisit for free(memdump) if needed.
>>>>>> +			del_timer(&qca->memdump_timer);
>>>>>> +			kfree(qca->qca_memdump);
>>>>>> +			qca->qca_memdump = NULL;
>>>>>> +			qca->memdump_state = QCA_MEMDUMP_COLLECTED;
>>>>>> +		}
>>>>>> +	}
>>>>>> +
>>>>>> +}
>>>>>> +
>>>>>> +int qca_controller_memdump_event(struct hci_dev *hdev, struct 
>>>>>> sk_buff *skb)
>>>>>> +{
>>>>>> +	struct hci_uart *hu = hci_get_drvdata(hdev);
>>>>>> +	struct qca_data *qca = hu->priv;
>>>>>> +
>>>>>> +	skb_queue_tail(&qca->rx_memdump_q, skb);
>>>>>> +	queue_work(qca->workqueue, &qca->ctrl_memdump_evt);
>>>>>> +
>>>>>> +	return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int qca_recv_event_data(struct hci_dev *hdev, struct 
>>>>>> sk_buff *skb)
>>>>>> +{
>>>>>> +	/* We receive chip memory dump as an event packet, With a 
>>>>>> dedicated
>>>>>> +	 * handler followed by a hardware error event. When this event 
>>>>>> is
>>>>>> +	 * received we store dump into a file before closing hci. This
>>>>>> +	 * dump will help in triaging the issues.
>>>>>> +	 */
>>>>>> +	if ((skb->data[0] == HCI_VENDOR_PKT) &&
>>>>>> +	    (get_unaligned_be16((skb->data) + 2) == 
>>>>>> QCA_SSR_DUMP_HANDLE))
>>>>> The (skb->data) is pointless, just do skb->data.
>>>> [Bala]: will update.
>>>>>> +		return qca_controller_memdump_event(hdev, skb);
>>>>>> +
>>>>>> +	return hci_recv_frame(hdev, skb);
>>>>>> +}
>>>>>> +
>>>>>> #define QCA_IBS_SLEEP_IND_EVENT \
>>>>>> 	.type = HCI_IBS_SLEEP_IND, \
>>>>>> 	.hlen = 0, \
>>>>>> @@ -888,12 +1089,12 @@ static int qca_recv_acl_data(struct hci_dev 
>>>>>> *hdev, struct sk_buff *skb)
>>>>>> 	.maxlen = HCI_MAX_IBS_SIZE
>>>>>> static const struct h4_recv_pkt qca_recv_pkts[] = {
>>>>>> -	{ H4_RECV_ACL,             .recv = qca_recv_acl_data },
>>>>>> -	{ H4_RECV_SCO,             .recv = hci_recv_frame    },
>>>>>> -	{ H4_RECV_EVENT,           .recv = hci_recv_frame    },
>>>>>> -	{ QCA_IBS_WAKE_IND_EVENT,  .recv = qca_ibs_wake_ind  },
>>>>>> -	{ QCA_IBS_WAKE_ACK_EVENT,  .recv = qca_ibs_wake_ack  },
>>>>>> -	{ QCA_IBS_SLEEP_IND_EVENT, .recv = qca_ibs_sleep_ind },
>>>>>> +	{ H4_RECV_ACL,             .recv = qca_recv_acl_data	},
>>>>>> +	{ H4_RECV_SCO,             .recv = hci_recv_frame	},
>>>>>> +	{ H4_RECV_EVENT,           .recv = qca_recv_event_data	},
>>>>> call it qca_recv_event and don't realign the whole table.
>>>> [Bala]: will update.
>>>>>> +	{ QCA_IBS_WAKE_IND_EVENT,  .recv = qca_ibs_wake_ind	},
>>>>>> +	{ QCA_IBS_WAKE_ACK_EVENT,  .recv = qca_ibs_wake_ack	},
>>>>>> +	{ QCA_IBS_SLEEP_IND_EVENT, .recv = qca_ibs_sleep_ind	},
>>>>>> };
>>>>>> static int qca_recv(struct hci_uart *hu, const void *data, int 
>>>>>> count)
>>>>>> @@ -1114,6 +1315,68 @@ static int qca_set_speed(struct hci_uart 
>>>>>> *hu, enum qca_speed_type speed_type)
>>>>>> 	return 0;
>>>>>> }
>>>>>> +static int qca_send_crashbuffer(struct hci_uart *hu)
>>>>>> +{
>>>>>> +	struct qca_data *qca = hu->priv;
>>>>>> +	struct sk_buff *skb;
>>>>>> +	unsigned char buf[QCA_CRASHBYTE_PACKET_LEN];
>>>>>> +
>>>>>> +	bt_dev_dbg(hu->hdev, "sending soc crash buffer to controller");
>>>>>> +
>>>>>> +	/* We forcefully crash the controller, by sending 0xfb byte for
>>>>>> +	 * 1024 times. We also might have chance of losing data, To be
>>>>>> +	 * on safer side we send 1100 bytes to the SoC.
>>>>>> +	 */
>>>>>> +	memset(buf, QCA_MEMDUMP_BYTE, QCA_CRASHBYTE_PACKET_LEN);
>>>>>> +
>>>>>> +	skb = bt_skb_alloc(QCA_CRASHBYTE_PACKET_LEN, GFP_KERNEL);
>>>>>> +	if (!skb) {
>>>>>> +		bt_dev_err(hu->hdev, "Failed to allocate memory for skb 
>>>>>> packet");
>>>>>> +		return -ENOMEM;
>>>>>> +	}
>>>>>> +
>>>>>> +	skb_put_data(skb, buf, QCA_CRASHBYTE_PACKET_LEN);
>>>>>> +	hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
>>>>>> +
>>>>>> +	skb_queue_tail(&qca->txq, skb);
>>>>>> +	hci_uart_tx_wakeup(hu);
>>>>>> +
>>>>>> +	return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static void qca_hw_error(struct hci_dev *hdev, u8 code)
>>>>>> +{
>>>>>> +	struct hci_uart *hu = hci_get_drvdata(hdev);
>>>>>> +	struct qca_data *qca = hu->priv;
>>>>>> +
>>>>>> +	bt_dev_info(hdev, "mem_dump_status: %d", qca->memdump_state);
>>>>>> +
>>>>>> +	if (qca->memdump_state == QCA_MEMDUMP_IDLE) {
>>>>>> +		/* If hardware error event received for other than QCA
>>>>>> +		 * soc memory dump event, then we need to crash the SOC
>>>>>> +		 * and wait here for 8 seconds to get the dump packets.
>>>>>> +		 * This will block main thread to be on hold until we
>>>>>> +		 * collect dump.
>>>>>> +		 */
>>>>>> +		mod_timer(&qca->memdump_timer,
>>>>>> +			  (jiffies + msecs_to_jiffies(qca->memdump_delay)));
>>>>> Why a timer that then ends up in interrupt context?
>>>> [Bala]: some times we only receive hardware error from the chip, so 
>>>> we are sending an special buffer to request the
>>>>       chip for memory dump. we are using an timer to check whether 
>>>> the data memdump is collected. if the timer
>>>>       over flows we are cleaning up all the assigned memory and 
>>>> unblock the main thread,
>>>>       in short this timer is a watch dog timer for the memory dump 
>>>> collection.
>>> I saw that you used a bunch of timers actually. My question is why 
>>> are
>>> these not delayed_wq instead? I wonder if we really want to keep 
>>> using
>>> timers and handling interrupt context locking if we could move
>>> everything to wq instead.
>> 
>> [Bala]: Let me brief you the requirement.
>>       This patch is used to collect the memory dump received from the 
>> chip and store it into a file.
>>       We receive chip memory dump in two cases
>>        1. When chip goes into the bad state it sends the dump followed 
>> by and hardware error event.
>>        2. Some time when we send some garbage or un recognized command 
>> to chip.
>>           it will respond with a hardware error event. So we send an 
>> 0xfb bytes to the chip requesting it to send the memory dump.
>> 
>> In both cases, chip will go into the bad state once it sends the dump. 
>> so we need to turn OFF and ON chip and perform the init procedure.
>> So keeping the above cases in the view, we register an handle for 
>> hardware error event. So that in both the cases hw error routine will 
>> execute.
>> 
>> As the dump as some specific headers we will queue the received data 
>> into work queue.
>> We are blocking the main thread until the total dump is stored into 
>> the file.
>> Here is the answer for the question, yes we check the status of the 
>> work queue but for handling case 2 we require timers.
>> But let us assume the wq is taking more time than expected. Then we 
>> also need a timer.
>> we are using timer so that we will not block the main thread 
>> indefinitely.
>> They are some cases where when we request a memory dump, after some 
>> packet sent by the chip.
>> it may go into a bad state where it will not pump the remaining dump, 
>> so we are using a timer to unblock the main thread.
>> so during timeout, we are restarting the flags to unblock the main 
>> thread.
>> 
>> 
>>>>>> +		qca_send_crashbuffer(hu);
>>>>>> +
>>>>>> +		while (qca->memdump_state != QCA_MEMDUMP_COLLECTED &&
>>>>>> +			qca->memdump_state != QCA_MEMDUMP_TIMEOUT)
>>>>>> +			;
>>>>> What is this? Busy loop? I rather not do that.
>>>> [Bala]: this busy required to collected the dump from the chip 
>>>> before we close an reopen the hci.
>>>>       >> +	} else if (qca->memdump_state == QCA_MEMDUMP_COLLECTING) 
>>>> {
>>> Why not use some wakeup handling here. I am really against any kind 
>>> of
>>> busy loops in a driver.
>> [Bala]: this busy loop is require. pls refer my comments to the above 
>> query.
>>        this will help in mainly in case 2, where we will block the 
>> main thread until we have dump collected.
>> 
>>        let us assume that we received an hardware error event, hw 
>> error routine we execute which sends an
>>        special byte to the chip requesting for memory dump. it starts 
>> sending the dump, but we move forward and turn off the
>>        chip so we will miss the dump. so here the busy loop is to wait 
>> until we have dump.
>>        but the we are not waiting indefinitely we have timer to 
>> unblock them.
> 
> I do not see how any of this is correct. Can you not use some wakeup
> helper like everybody else does. I also do not see how these two
> threads are correctly protected. It looks really hackish to me.
> 
> Regards
> 
> Marcel

Ok sure, will check and update accordingly in the incremental patch.

-- 
Regards
Balakrishna.

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