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From:   Hector Martin <marcan@marcan.st>
Cc:     Hector Martin <marcan@marcan.st>,
        Anup Patel <anup.patel@broadcom.com>,
        Vinod Koul <vkoul@kernel.org>, Sven Peter <sven@svenpeter.dev>,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>,
        Mun Yew Tham <mun.yew.tham@intel.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Arnd Bergmann <arnd@arndb.de>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev
Subject: [PATCH 6/7] mailbox: apple: Implement flush() operation
Date:   Mon,  2 May 2022 18:02:24 +0900
Message-Id: <20220502090225.26478-7-marcan@marcan.st>
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This allows clients to use the atomic-safe mailbox API style.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
 drivers/mailbox/apple-mailbox.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/mailbox/apple-mailbox.c b/drivers/mailbox/apple-mailbox.c
index 496c4951ccb1..33e7acf71e3e 100644
--- a/drivers/mailbox/apple-mailbox.c
+++ b/drivers/mailbox/apple-mailbox.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/apple-mailbox.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/gfp.h>
 #include <linux/interrupt.h>
@@ -112,6 +113,14 @@ static bool apple_mbox_hw_can_send(struct apple_mbox *apple_mbox)
 	return !(mbox_ctrl & apple_mbox->hw->control_full);
 }
 
+static bool apple_mbox_hw_send_empty(struct apple_mbox *apple_mbox)
+{
+	u32 mbox_ctrl =
+		readl_relaxed(apple_mbox->regs + apple_mbox->hw->a2i_control);
+
+	return mbox_ctrl & apple_mbox->hw->control_empty;
+}
+
 static int apple_mbox_hw_send(struct apple_mbox *apple_mbox,
 			      struct apple_mbox_msg *msg)
 {
@@ -219,6 +228,23 @@ static irqreturn_t apple_mbox_recv_irq(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static int apple_mbox_chan_flush(struct mbox_chan *chan, unsigned long timeout)
+{
+	struct apple_mbox *apple_mbox = chan->con_priv;
+	unsigned long deadline = jiffies + msecs_to_jiffies(timeout);
+
+	while (time_before(jiffies, deadline)) {
+		if (apple_mbox_hw_send_empty(apple_mbox)) {
+			mbox_chan_txdone(&apple_mbox->chan, 0);
+			return 0;
+		}
+
+		udelay(1);
+	}
+
+	return -ETIME;
+}
+
 static int apple_mbox_chan_startup(struct mbox_chan *chan)
 {
 	struct apple_mbox *apple_mbox = chan->con_priv;
@@ -250,6 +276,7 @@ static void apple_mbox_chan_shutdown(struct mbox_chan *chan)
 
 static const struct mbox_chan_ops apple_mbox_ops = {
 	.send_data = apple_mbox_chan_send_data,
+	.flush = apple_mbox_chan_flush,
 	.startup = apple_mbox_chan_startup,
 	.shutdown = apple_mbox_chan_shutdown,
 };
-- 
2.35.1