linux-kernel - [PATCH v2 2/4] media: sunxi-cir: Remove unnecessary spinlock

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Date:   Mon, 18 Jan 2021 00:00:46 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Sean Young <sean@...s.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com, Samuel Holland <samuel@...lland.org>
Subject: [PATCH v2 2/4] media: sunxi-cir: Remove unnecessary spinlock

Only one register, SUNXI_IR_CIR_REG, is accessed from outside the
interrupt handler, and that register is not accessed from inside it.
As there is no overlap between different contexts, no lock is needed.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---
 drivers/media/rc/sunxi-cir.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/media/rc/sunxi-cir.c b/drivers/media/rc/sunxi-cir.c
index 0a7f7eab3cc3..48be400421cd 100644
--- a/drivers/media/rc/sunxi-cir.c
+++ b/drivers/media/rc/sunxi-cir.c
@@ -86,7 +86,6 @@ struct sunxi_ir_quirks {
 };
 
 struct sunxi_ir {
-	spinlock_t      ir_lock;
 	struct rc_dev   *rc;
 	void __iomem    *base;
 	int             irq;
@@ -105,8 +104,6 @@ static irqreturn_t sunxi_ir_irq(int irqno, void *dev_id)
 	struct sunxi_ir *ir = dev_id;
 	struct ir_raw_event rawir = {};
 
-	spin_lock(&ir->ir_lock);
-
 	status = readl(ir->base + SUNXI_IR_RXSTA_REG);
 
 	/* clean all pending statuses */
@@ -137,8 +134,6 @@ static irqreturn_t sunxi_ir_irq(int irqno, void *dev_id)
 		ir_raw_event_handle(ir->rc);
 	}
 
-	spin_unlock(&ir->ir_lock);
-
 	return IRQ_HANDLED;
 }
 
@@ -160,17 +155,14 @@ static int sunxi_ir_set_timeout(struct rc_dev *rc_dev, unsigned int timeout)
 {
 	struct sunxi_ir *ir = rc_dev->priv;
 	unsigned int base_clk = clk_get_rate(ir->clk);
-	unsigned long flags;
 
 	unsigned int ithr = sunxi_usec_to_ithr(base_clk, timeout);
 
 	dev_dbg(rc_dev->dev.parent, "setting idle threshold to %u\n", ithr);
 
-	spin_lock_irqsave(&ir->ir_lock, flags);
 	/* Set noise threshold and idle threshold */
 	writel(REG_CIR_NTHR(SUNXI_IR_RXNOISE) | REG_CIR_ITHR(ithr),
 	       ir->base + SUNXI_IR_CIR_REG);
-	spin_unlock_irqrestore(&ir->ir_lock, flags);
 
 	rc_dev->timeout = sunxi_ithr_to_usec(base_clk, ithr);
 
@@ -199,8 +191,6 @@ static int sunxi_ir_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	spin_lock_init(&ir->ir_lock);
-
 	ir->fifo_size = quirks->fifo_size;
 
 	/* Clock */
-- 
2.26.2