linux-kernel - [UPDATE][PATCH 1/2] mailbox: reset txdone_method TXDONE_BY_POLL if client knows

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Date:   Mon,  3 Jul 2017 17:41:13 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     LKML <linux-kernel@...r.kernel.org>,
        Jassi Brar <jassisinghbrar@...il.com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Alexey Klimov <alexey.klimov@....com>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: [UPDATE][PATCH 1/2] mailbox: reset txdone_method TXDONE_BY_POLL if client knows_txdone

Currently the mailbox framework sets txdone_method to TXDONE_BY_POLL if
the controller sets txdone_by_poll. However some clients can have a
mechanism to do TXDONE_BY_ACK which they can specify by knows_txdone.
However, we endup setting both TXDONE_BY_POLL and TXDONE_BY_ACK in that
case. In such scenario, we may end up with below warnings as the tx
ticker is run both by mailbox framework and the client.

WARNING: CPU: 1 PID: 0 at kernel/time/hrtimer.c:805 hrtimer_forward+0x88/0xd8
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.12.0-rc5 #242
Hardware name: ARM LTD ARM Juno Development Platform
task: ffff8009768ca700 task.stack: ffff8009768f8000
PC is at hrtimer_forward+0x88/0xd8
LR is at txdone_hrtimer+0xd4/0xf8
Call trace:
 hrtimer_forward+0x88/0xd8
 __hrtimer_run_queues+0xe4/0x158
 hrtimer_interrupt+0xa4/0x220
 arch_timer_handler_phys+0x30/0x40
 handle_percpu_devid_irq+0x78/0x130
 generic_handle_irq+0x24/0x38
 __handle_domain_irq+0x5c/0xb8
 gic_handle_irq+0x54/0xa8

This patch fixes the issue by resetting TXDONE_BY_POLL if client has set
knows_txdone.

Cc: Alexey Klimov <alexey.klimov@....com>
Cc: Jassi Brar <jaswinder.singh@...aro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/mailbox/mailbox.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 537f4f6d009b..674b35f402f5 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -351,7 +351,7 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
 	init_completion(&chan->tx_complete);
 
 	if (chan->txdone_method	== TXDONE_BY_POLL && cl->knows_txdone)
-		chan->txdone_method |= TXDONE_BY_ACK;
+		chan->txdone_method = TXDONE_BY_ACK;
 
 	spin_unlock_irqrestore(&chan->lock, flags);
 
@@ -418,7 +418,7 @@ void mbox_free_channel(struct mbox_chan *chan)
 	spin_lock_irqsave(&chan->lock, flags);
 	chan->cl = NULL;
 	chan->active_req = NULL;
-	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
+	if (chan->txdone_method == TXDONE_BY_ACK)
 		chan->txdone_method = TXDONE_BY_POLL;
 
 	module_put(chan->mbox->dev->driver->owner);
-- 
2.7.4