linux-kernel - [PATCH v2 09/11] i3c: master: svc: use spinlock_saveirq at svc_i3c_master_ibi

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Message-Id: <20240813-i3c_fix-v2-9-68fe4a050188@nxp.com>
Date: Tue, 13 Aug 2024 11:15:07 -0400
From: Frank Li <Frank.Li@....com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 Boris Brezillon <boris.brezillon@...labora.com>, 
 Parshuram Thombare <pthombar@...ence.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Boris Brezillon <bbrezillon@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, 
 Conor Culhane <conor.culhane@...vaco.com>
Cc: linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 imx@...ts.linux.dev, Frank Li <Frank.Li@....com>
Subject: [PATCH v2 09/11] i3c: master: svc: use spinlock_saveirq at
 svc_i3c_master_ibi_work()

According to I3C spec ver 1.1, 09-Jun-2021, section 5.1.2.5:

The I3C Controller shall hold SCL Low while the Bus is in I3C/I2C Transfer,
ACK/NACK Phase. But maximum stall time is 100us. We have to disable irq and
schedule during whole I3C transaction, otherwise, I3C bus timeout will
happen if any irq or schedule happen during transaction.

Replace mutex with spinlock_saveirq() to make sure finish whole i3c
transaction without stall SCL more than 100us.

Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/i3c/master/svc-i3c-master.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 161ccd824443b..fbb6cef405577 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -432,7 +432,16 @@ static void svc_i3c_master_ibi_work(struct work_struct *work)
 	u32 status, val;
 	int ret;
 
-	mutex_lock(&master->lock);
+	/*
+	 * According to I3C spec ver 1.1, 09-Jun-2021, section 5.1.2.5:
+	 *
+	 * The I3C Controller shall hold SCL Low while the Bus is in I3C/I2C Transfer, ACK/NACK
+	 * Phase. But maximum stall time is 100us. We have to disable irq and schedule during whole
+	 * I3C transaction, otherwise, I3C bus timeout will happen if any irq or schedule happen
+	 * between transaction..
+	 */
+	guard(spinlock_irqsave)(&master->xferqueue.lock);
+
 	/*
 	 * IBIWON may be set before SVC_I3C_MCTRL_REQUEST_AUTO_IBI, causing
 	 * readl_relaxed_poll_timeout() to return immediately. Consequently,
@@ -452,7 +461,7 @@ static void svc_i3c_master_ibi_work(struct work_struct *work)
 	       master->regs + SVC_I3C_MCTRL);
 
 	/* Wait for IBIWON, should take approximately 100us */
-	ret = readl_relaxed_poll_timeout(master->regs + SVC_I3C_MSTATUS, val,
+	ret = readl_relaxed_poll_timeout_atomic(master->regs + SVC_I3C_MSTATUS, val,
 					 SVC_I3C_MSTATUS_IBIWON(val), 0, 1000);
 	if (ret) {
 		dev_err(master->dev, "Timeout when polling for IBIWON\n");
@@ -525,7 +534,6 @@ static void svc_i3c_master_ibi_work(struct work_struct *work)
 
 reenable_ibis:
 	svc_i3c_master_enable_interrupts(master, SVC_I3C_MINT_SLVSTART);
-	mutex_unlock(&master->lock);
 }
 
 static irqreturn_t svc_i3c_master_irq_handler(int irq, void *dev_id)

-- 
2.34.1