[PATCHv4 0/2] Adding driver for Xilinx LogiCORE IP mailbox.

[PATCHv4 0/2] Adding driver for Xilinx LogiCORE IP mailbox.

[Moritz Fischer]

This patchset adds mailbox framework integration for the Xilinx LogiCORE IP
mailbox.  The Xilinx LogiCORE IP mailbox is a fpga softcore that allows
interprocessor communication between AXI4 stream / memory mapped
processors.

Changes from v3:
- Stylistic changes
- Changed reg size in dts to 0x100

Changes from v2:
- Fixed error condition for IRQ from >= 0 to > 0
- Fixed clock enable
- Cleaned up docs

Changes from v1:
- Added common clock framework support
- Deal with IRQs that happend before driver load,
  since HW will not let us know about them when we enable IRQs

Changes from v0:
- Several stylistic issues
- Dropped superfluous intr_mode member
- Really masking the IRQs on mailbox_shutdown
- No longer using polling by accident in non-IRQ mode
- Swapped doc and driver commits

Happy hacking,

Moritz

Moritz Fischer (2):
  dts: Adding docs for Xilinx LogiCORE IP mailbox driver.
  mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

 .../bindings/mailbox/xilinx-mailbox.txt         |  44 +++
 MAINTAINERS                                     |   7 +
 drivers/mailbox/Kconfig                         |   8 +
 drivers/mailbox/Makefile                        |   2 +
 drivers/mailbox/mailbox-xilinx.c                | 352 +++++++++++++++++++
 5 files changed, 413 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
 create mode 100644 drivers/mailbox/mailbox-xilinx.c

-- 
2.4.1

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[PATCHv4 1/2] dts: Adding docs for Xilinx LogiCORE IP mailbox driver.

[Moritz Fischer]

Changes from v3:
- Changed reg size to 0x100

Changes from v2:
- Addressed Michal's stylistic comments
- Fixed typo in compatible string

Changes from v1:
- Added common clock framework support

Changes from v0:
- Fixed example bindings

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
---
 .../bindings/mailbox/xilinx-mailbox.txt         | 44 ++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt b/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
new file mode 100644
index 0000000..f9ec46d
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
@@ -0,0 +1,44 @@
+Xilinx Mailbox Driver
+=====================
+
+Required properties:
+- compatible       : "xlnx,mailbox-2.1".
+- reg              :  physical base address of the mailbox and length of
+                      memory mapped region.
+- #mbox-cells      :  common mailbox binding property to identify the number
+                      of cells required for the mailbox specifier, should be 1
+- clocks           :  phandle to clock provider
+- clock-names      :  must be 'mbox'
+
+Optional properties:
+- interrupt-parent : interrupt source phandle
+- interrupts       : interrupt number, The interrupt specifier format
+                     depends on the interrupt controller parent.
+
+Example:
+	mbox: mailbox@40400000 {
+		compatible = "xlnx,mailbox-2.1";
+		reg = <0x40400000 0x100>;
+		interrupt-parent = <&intc>;
+		interrupts = <5>;
+		#mbox-cells = <1>;
+		clocks = <&clkc 15>;
+		clock-names = "mbox";
+	};
+
+Mailbox client
+===============
+"mboxes" and the optional "mbox-names" (please see
+Documentation/devicetree/bindings/mailbox/mailbox.txt for details). Each value
+of the mboxes property should contain a phandle to the mailbox controller
+device node and second argument is the channel index. It must be 0 (hardware
+support only one channel). The equivalent "mbox-names" property value can be
+used to give a name to the communication channel to be used by the client user.
+
+Example:
+	mclient0: mclient0@400 {
+		compatible = "client-1.0";
+		reg = <0x400 0x10>;
+		mbox-names = "mbox";
+		mboxes = <&mbox 0>;
+	};
-- 
2.4.1

Re: [PATCHv4 1/2] dts: Adding docs for Xilinx LogiCORE IP mailbox driver.

[Josh Cartwright]

[-- Attachment #1: Type: text/plain, Size: 1441 bytes --]

On Mon, Jun 01, 2015 at 09:18:26AM -0700, Moritz Fischer wrote:
> Changes from v3:
> - Changed reg size to 0x100
> 
> Changes from v2:
> - Addressed Michal's stylistic comments
> - Fixed typo in compatible string
> 
> Changes from v1:
> - Added common clock framework support
> 
> Changes from v0:
> - Fixed example bindings
> 
> Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
> Acked-by: Michal Simek <michal.simek@xilinx.com>
> ---
>  .../bindings/mailbox/xilinx-mailbox.txt         | 44 ++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt b/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
> new file mode 100644
> index 0000000..f9ec46d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
> @@ -0,0 +1,44 @@
> +Xilinx Mailbox Driver
> +=====================
> +
> +Required properties:
> +- compatible       : "xlnx,mailbox-2.1".
> +- reg              :  physical base address of the mailbox and length of
> +                      memory mapped region.
> +- #mbox-cells      :  common mailbox binding property to identify the number
> +                      of cells required for the mailbox specifier, should be 1

It seems strange to me to require #mbox-cells = <1>, when this hardware
only supports a single channel.  Why not #mbox-cells = <0>; ?

  Josh

[-- Attachment #2: Type: application/pgp-signature, Size: 473 bytes --]

[PATCHv4 2/2] mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

[Moritz Fischer]

The Xilinx LogiCORE IP mailbox is a FPGA core that allows for
interprocessor communication via AXI4 memory mapped / AXI4 stream
interfaces.

It is single channel per core and allows for transmit and receive.

Changes from v3:
- Stylistic

Changes from v2:
- Fixed error handling for IRQ from >= 0 to > 0
- Fixed error handling for clock enabling
- Addressed Michal's stylistic comments

Changes from v1:
- Added common clock framework support
- Deal with IRQs that happend before driver load,
  since HW will not let us know about them when we enable IRQs

Changes from v0:
- Several stylistic issues
- Dropped superfluous intr_mode member
- Really masking the IRQs on mailbox_shutdown
- No longer using polling by accident in non-IRQ mode
- Swapped doc and driver commits

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
---
 MAINTAINERS                      |   7 +
 drivers/mailbox/Kconfig          |   8 +
 drivers/mailbox/Makefile         |   2 +
 drivers/mailbox/mailbox-xilinx.c | 352 ++++++++++++++++++++++++++++++++++
 4 files changed, 369 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index f8e0afb..f1f0d10 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10986,6 +10986,13 @@ M:	John Linn <John.Linn@xilinx.com>
 S:	Maintained
 F:	drivers/net/ethernet/xilinx/xilinx_axienet*
 
+XILINX MAILBOX DRIVER
+M:	Moritz Fischer <moritz.fischer@ettus.com>
+L:	linux-kernel@vger.kernel.org
+S:	Maintained
+F:	drivers/mailbox/mailbox-xilinx.c
+F:	Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
+
 XILINX UARTLITE SERIAL DRIVER
 M:	Peter Korsgaard <jacmet@sunsite.dk>
 L:	linux-serial@vger.kernel.org
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 84b0a2d..e11e4b2 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -60,4 +60,12 @@ config ALTERA_MBOX
 	  An implementation of the Altera Mailbox soft core. It is used
 	  to send message between processors. Say Y here if you want to use the
 	  Altera mailbox support.
+
+config XILINX_MBOX
+	tristate "Xilinx Mailbox"
+	help
+	  An implementation of the Xilinx Mailbox soft core. It is used
+	  to send message between processors. Say Y here if you want to use the
+	  Xilinx mailbox support.
+
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index b18201e..d28a028 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -11,3 +11,5 @@ obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o
 obj-$(CONFIG_PCC)		+= pcc.o
 
 obj-$(CONFIG_ALTERA_MBOX)	+= mailbox-altera.o
+
+obj-$(CONFIG_XILINX_MBOX)	+= mailbox-xilinx.o
diff --git a/drivers/mailbox/mailbox-xilinx.c b/drivers/mailbox/mailbox-xilinx.c
new file mode 100644
index 0000000..f1c88e4
--- /dev/null
+++ b/drivers/mailbox/mailbox-xilinx.c
@@ -0,0 +1,352 @@
+/*
+ * Copyright (c) 2015, National Instruments Corp. All rights reserved.
+ *
+ * Driver for the Xilinx LogiCORE mailbox IP block
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define DRIVER_NAME "xilinx-mailbox"
+
+/* register offsets */
+#define MAILBOX_REG_WRDATA	0x00
+#define MAILBOX_REG_RDDATA	0x08
+#define MAILBOX_REG_STATUS	0x10
+#define MAILBOX_REG_ERROR	0x14
+#define MAILBOX_REG_SIT	0x18
+#define MAILBOX_REG_RIT	0x1c
+#define MAILBOX_REG_IS	0x20
+#define MAILBOX_REG_IE	0x24
+#define MAILBOX_REG_IP	0x28
+
+/* status register */
+#define STS_RTA	BIT(3)
+#define STS_STA	BIT(2)
+#define STS_FULL	BIT(1)
+#define STS_EMPTY	BIT(0)
+
+/* error register */
+#define ERR_FULL	BIT(1)
+#define ERR_EMPTY	BIT(0)
+
+/* mailbox interrupt status register */
+#define INT_STATUS_ERR	BIT(2)
+#define INT_STATUS_RTI	BIT(1)
+#define INT_STATUS_STI	BIT(0)
+
+/* mailbox interrupt enable register */
+#define INT_ENABLE_ERR	BIT(2)
+#define INT_ENABLE_RTI	BIT(1)
+#define INT_ENABLE_STI	BIT(0)
+
+#define MBOX_POLLING_MS		5	/* polling interval 5ms */
+
+struct xilinx_mbox {
+	int irq;
+	void __iomem *mbox_base;
+	struct clk *clk;
+	struct device *dev;
+	struct mbox_controller controller;
+
+	/* if the controller supports only RX polling mode */
+	struct timer_list rxpoll_timer;
+};
+
+static struct xilinx_mbox *mbox_chan_to_xilinx_mbox(struct mbox_chan *chan)
+{
+	if (!chan || !chan->con_priv)
+		return NULL;
+
+	return (struct xilinx_mbox *)chan->con_priv;
+}
+
+static inline bool xilinx_mbox_full(struct xilinx_mbox *mbox)
+{
+	u32 status;
+
+	status = readl_relaxed(mbox->mbox_base + MAILBOX_REG_STATUS);
+
+	return status & STS_FULL;
+}
+
+static inline bool xilinx_mbox_pending(struct xilinx_mbox *mbox)
+{
+	u32 status;
+
+	status = readl_relaxed(mbox->mbox_base + MAILBOX_REG_STATUS);
+
+	return !(status & STS_EMPTY);
+}
+
+static void xilinx_mbox_intmask(struct xilinx_mbox *mbox, u32 mask, bool enable)
+{
+	u32 mask_reg;
+
+	mask_reg = readl_relaxed(mbox->mbox_base + MAILBOX_REG_IE);
+	if (enable)
+		mask_reg |= mask;
+	else
+		mask_reg &= ~mask;
+
+	writel_relaxed(mask_reg, mbox->mbox_base + MAILBOX_REG_IE);
+}
+
+
+static inline void xilinx_mbox_rx_intmask(struct xilinx_mbox *mbox, bool enable)
+{
+	xilinx_mbox_intmask(mbox, INT_ENABLE_RTI, enable);
+}
+
+static inline void xilinx_mbox_tx_intmask(struct xilinx_mbox *mbox, bool enable)
+{
+	xilinx_mbox_intmask(mbox, INT_ENABLE_STI, enable);
+}
+
+static void xilinx_mbox_rx_data(struct mbox_chan *chan)
+{
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+	u32 data;
+
+	if (xilinx_mbox_pending(mbox)) {
+		data = readl_relaxed(mbox->mbox_base + MAILBOX_REG_RDDATA);
+		mbox_chan_received_data(chan, (void *)data);
+	}
+}
+
+static void xilinx_mbox_poll_rx(unsigned long data)
+{
+	struct mbox_chan *chan = (struct mbox_chan *)data;
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	xilinx_mbox_rx_data(chan);
+
+	mod_timer(&mbox->rxpoll_timer,
+		  jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
+}
+
+static irqreturn_t xilinx_mbox_interrupt(int irq, void *p)
+{
+	u32 mask;
+	struct mbox_chan *chan = (struct mbox_chan *)p;
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	mask = readl_relaxed(mbox->mbox_base + MAILBOX_REG_IS);
+	if (mask & INT_STATUS_RTI)
+		xilinx_mbox_rx_data(chan);
+
+	/* mask irqs *before* notifying done, require tx_block=true */
+	if (mask & INT_STATUS_STI) {
+		xilinx_mbox_tx_intmask(mbox, false);
+		mbox_chan_txdone(chan, 0);
+	}
+
+	writel_relaxed(mask, mbox->mbox_base + MAILBOX_REG_IS);
+
+	return IRQ_HANDLED;
+}
+
+static int xilinx_mbox_startup(struct mbox_chan *chan)
+{
+	int ret;
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	if (mbox->irq > 0) {
+		ret = request_irq(mbox->irq, xilinx_mbox_interrupt, 0,
+				  dev_name(mbox->dev), chan);
+		if (unlikely(ret)) {
+			dev_err(mbox->dev,
+				"failed to register mailbox interrupt:%d\n",
+				ret);
+			return ret;
+		}
+
+		xilinx_mbox_rx_intmask(mbox, true);
+
+		/* if fifo was full already, we didn't get an interrupt */
+		while (xilinx_mbox_pending(mbox))
+			xilinx_mbox_rx_data(chan);
+
+		return 0;
+	}
+
+	/* setup polling timer */
+	setup_timer(&mbox->rxpoll_timer, xilinx_mbox_poll_rx,
+		    (unsigned long)chan);
+	mod_timer(&mbox->rxpoll_timer,
+		  jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
+
+	return 0;
+}
+
+static int xilinx_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+	u32 *udata = (u32 *)data;
+
+	if (!mbox || !data)
+		return -EINVAL;
+
+	if (xilinx_mbox_full(mbox))
+		return -EBUSY;
+
+	/* enable interrupt before send */
+	if (mbox->irq >= 0)
+		xilinx_mbox_tx_intmask(mbox, true);
+
+	writel_relaxed(*udata, mbox->mbox_base + MAILBOX_REG_WRDATA);
+
+	return 0;
+}
+
+static bool xilinx_mbox_last_tx_done(struct mbox_chan *chan)
+{
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	/* return false if mailbox is full */
+	return !xilinx_mbox_full(mbox);
+}
+
+static bool xilinx_mbox_peek_data(struct mbox_chan *chan)
+{
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	return xilinx_mbox_pending(mbox);
+}
+
+static void xilinx_mbox_shutdown(struct mbox_chan *chan)
+{
+	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
+
+	if (mbox->irq > 0) {
+		/* mask all interrupts */
+		writel_relaxed(0, mbox->mbox_base + MAILBOX_REG_IE);
+		free_irq(mbox->irq, chan);
+	} else {
+		del_timer_sync(&mbox->rxpoll_timer);
+	}
+}
+
+static struct mbox_chan_ops xilinx_mbox_ops = {
+	.send_data = xilinx_mbox_send_data,
+	.startup = xilinx_mbox_startup,
+	.shutdown = xilinx_mbox_shutdown,
+	.last_tx_done = xilinx_mbox_last_tx_done,
+	.peek_data = xilinx_mbox_peek_data,
+};
+
+static int xilinx_mbox_probe(struct platform_device *pdev)
+{
+	struct xilinx_mbox *mbox;
+	struct resource	*regs;
+	struct mbox_chan *chans;
+	int ret;
+
+	mbox = devm_kzalloc(&pdev->dev, sizeof(*mbox), GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+
+	/* get clk and enable */
+	mbox->clk = devm_clk_get(&pdev->dev, "mbox");
+	if (IS_ERR(mbox->clk)) {
+		dev_err(&pdev->dev, "Couldn't get clk.\n");
+		return PTR_ERR(mbox->clk);
+	}
+
+	/* allocated one channel */
+	chans = devm_kzalloc(&pdev->dev, sizeof(*chans), GFP_KERNEL);
+	if (!chans)
+		return -ENOMEM;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+	mbox->mbox_base = devm_ioremap_resource(&pdev->dev, regs);
+	if (IS_ERR(mbox->mbox_base))
+		return PTR_ERR(mbox->mbox_base);
+
+	mbox->irq = platform_get_irq(pdev, 0);
+	/* if irq is present, we can use it, otherwise, poll */
+	if (mbox->irq > 0) {
+		mbox->controller.txdone_irq = true;
+	} else {
+		dev_info(&pdev->dev, "IRQ not found, fallback to polling.\n");
+		mbox->controller.txdone_poll = true;
+		mbox->controller.txpoll_period = MBOX_POLLING_MS;
+	}
+
+	mbox->dev = &pdev->dev;
+
+	/* hardware supports only one channel. */
+	chans[0].con_priv = mbox;
+	mbox->controller.dev = mbox->dev;
+	mbox->controller.num_chans = 1;
+	mbox->controller.chans = chans;
+	mbox->controller.ops = &xilinx_mbox_ops;
+
+	/* prep and enable the clock */
+	clk_prepare_enable(mbox->clk);
+
+	ret = mbox_controller_register(&mbox->controller);
+	if (ret) {
+		dev_err(&pdev->dev, "Register mailbox failed\n");
+		clk_disable_unprepare(mbox->clk);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, mbox);
+
+	return 0;
+}
+
+static int xilinx_mbox_remove(struct platform_device *pdev)
+{
+	struct xilinx_mbox *mbox = platform_get_drvdata(pdev);
+
+	if (!mbox)
+		return -EINVAL;
+
+	mbox_controller_unregister(&mbox->controller);
+
+	clk_disable_unprepare(mbox->clk);
+
+	return 0;
+}
+
+static const struct of_device_id xilinx_mbox_match[] = {
+	{ .compatible = "xlnx,mailbox-2.1" },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, xilinx_mbox_match);
+
+static struct platform_driver xilinx_mbox_driver = {
+	.probe	= xilinx_mbox_probe,
+	.remove	= xilinx_mbox_remove,
+	.driver	= {
+		.name	= DRIVER_NAME,
+		.of_match_table	= xilinx_mbox_match,
+	},
+};
+
+module_platform_driver(xilinx_mbox_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Xilinx mailbox specific functions");
+MODULE_AUTHOR("Moritz Fischer <moritz.fischer@ettus.com>");
+MODULE_ALIAS("platform:xilinx-mailbox");
-- 
2.4.1

Re: [PATCHv4 2/2] mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

[Joe Perches]

On Mon, 2015-06-01 at 09:18 -0700, Moritz Fischer wrote:
> The Xilinx LogiCORE IP mailbox is a FPGA core that allows for
> interprocessor communication via AXI4 memory mapped / AXI4 stream
> interfaces.

trivia:

> diff --git a/drivers/mailbox/mailbox-xilinx.c b/drivers/mailbox/mailbox-xilinx.c
[]
> +static int xilinx_mbox_startup(struct mbox_chan *chan)
> +{
[]
> +			dev_err(mbox->dev,
> +				"failed to register mailbox interrupt:%d\n",
> +				ret);
[]
> +static int xilinx_mbox_probe(struct platform_device *pdev)
> +{
[]
> +		dev_err(&pdev->dev, "Couldn't get clk.\n");
[]
> +		dev_info(&pdev->dev, "IRQ not found, fallback to polling.\n");
[]
> +		dev_err(&pdev->dev, "Register mailbox failed\n");

Perhaps it' be nicer to consistently use a "no-period"
message style.


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Re: [PATCHv4 2/2] mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

[Josh Cartwright]

[-- Attachment #1: Type: text/plain, Size: 8871 bytes --]

Hey Moritz-

A few comments below:

On Mon, Jun 01, 2015 at 09:18:27AM -0700, Moritz Fischer wrote:
[..]
> +++ b/drivers/mailbox/mailbox-xilinx.c
> @@ -0,0 +1,352 @@
> +/*
> + * Copyright (c) 2015, National Instruments Corp. All rights reserved.
> + *
> + * Driver for the Xilinx LogiCORE mailbox IP block
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +#define DRIVER_NAME "xilinx-mailbox"

Does KBUILD_MODNAME already give you what you need?

> +
> +/* register offsets */
> +#define MAILBOX_REG_WRDATA	0x00
> +#define MAILBOX_REG_RDDATA	0x08
> +#define MAILBOX_REG_STATUS	0x10
> +#define MAILBOX_REG_ERROR	0x14
> +#define MAILBOX_REG_SIT	0x18
> +#define MAILBOX_REG_RIT	0x1c
> +#define MAILBOX_REG_IS	0x20
> +#define MAILBOX_REG_IE	0x24
> +#define MAILBOX_REG_IP	0x28
> +
> +/* status register */
> +#define STS_RTA	BIT(3)
> +#define STS_STA	BIT(2)
> +#define STS_FULL	BIT(1)
> +#define STS_EMPTY	BIT(0)
> +
> +/* error register */
> +#define ERR_FULL	BIT(1)
> +#define ERR_EMPTY	BIT(0)
> +
> +/* mailbox interrupt status register */
> +#define INT_STATUS_ERR	BIT(2)
> +#define INT_STATUS_RTI	BIT(1)
> +#define INT_STATUS_STI	BIT(0)
> +
> +/* mailbox interrupt enable register */
> +#define INT_ENABLE_ERR	BIT(2)
> +#define INT_ENABLE_RTI	BIT(1)
> +#define INT_ENABLE_STI	BIT(0)
> +
> +#define MBOX_POLLING_MS		5	/* polling interval 5ms */
> +
> +struct xilinx_mbox {
> +	int irq;
> +	void __iomem *mbox_base;
> +	struct clk *clk;
> +	struct device *dev;
> +	struct mbox_controller controller;
> +
> +	/* if the controller supports only RX polling mode */
> +	struct timer_list rxpoll_timer;
> +};
> +
> +static struct xilinx_mbox *mbox_chan_to_xilinx_mbox(struct mbox_chan *chan)
> +{
> +	if (!chan || !chan->con_priv)

The chan->con_priv check is unnecessary.

> +		return NULL;
> +
> +	return (struct xilinx_mbox *)chan->con_priv;

Nit: Unnecessary cast.

[..]
> +static int xilinx_mbox_startup(struct mbox_chan *chan)
> +{
> +	int ret;
> +	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
> +
> +	if (mbox->irq > 0) {
> +		ret = request_irq(mbox->irq, xilinx_mbox_interrupt, 0,
> +				  dev_name(mbox->dev), chan);
> +		if (unlikely(ret)) {
> +			dev_err(mbox->dev,
> +				"failed to register mailbox interrupt:%d\n",
> +				ret);
> +			return ret;
> +		}
> +
> +		xilinx_mbox_rx_intmask(mbox, true);
> +
> +		/* if fifo was full already, we didn't get an interrupt */
> +		while (xilinx_mbox_pending(mbox))
> +			xilinx_mbox_rx_data(chan);
> +
> +		return 0;
> +	}
> +
> +	/* setup polling timer */
> +	setup_timer(&mbox->rxpoll_timer, xilinx_mbox_poll_rx,
> +		    (unsigned long)chan);
> +	mod_timer(&mbox->rxpoll_timer,
> +		  jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
> +
> +	return 0;
> +}
> +
> +static int xilinx_mbox_send_data(struct mbox_chan *chan, void *data)
> +{
> +	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
> +	u32 *udata = (u32 *)data;

Nit: Unnecessary cast.

> +
> +	if (!mbox || !data)
> +		return -EINVAL;
> +
> +	if (xilinx_mbox_full(mbox))
> +		return -EBUSY;
> +
> +	/* enable interrupt before send */
> +	if (mbox->irq >= 0)

You seem to be inconsistent in checking mbox->irq >=0 (here) vs. >0 (in
probe).

> +		xilinx_mbox_tx_intmask(mbox, true);
> +
> +	writel_relaxed(*udata, mbox->mbox_base + MAILBOX_REG_WRDATA);
> +
> +	return 0;
> +}
> +
> +static bool xilinx_mbox_last_tx_done(struct mbox_chan *chan)
> +{
> +	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
> +
> +	/* return false if mailbox is full */
> +	return !xilinx_mbox_full(mbox);
> +}
> +
> +static bool xilinx_mbox_peek_data(struct mbox_chan *chan)
> +{
> +	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
> +
> +	return xilinx_mbox_pending(mbox);

> +
> +static void xilinx_mbox_shutdown(struct mbox_chan *chan)
> +{
> +	struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
> +
> +	if (mbox->irq > 0) {
> +		/* mask all interrupts */
> +		writel_relaxed(0, mbox->mbox_base + MAILBOX_REG_IE);
> +		free_irq(mbox->irq, chan);
> +	} else {
> +		del_timer_sync(&mbox->rxpoll_timer);
> +	}
> +}
> +
> +static struct mbox_chan_ops xilinx_mbox_ops = {

const?

I'm also wondering if it's a bit cleaner to define two mbox_ops, one for
polling and one for when the device is interrupt driven.

> +	.send_data = xilinx_mbox_send_data,
> +	.startup = xilinx_mbox_startup,
> +	.shutdown = xilinx_mbox_shutdown,
> +	.last_tx_done = xilinx_mbox_last_tx_done,
> +	.peek_data = xilinx_mbox_peek_data,
> +};
> +
> +static int xilinx_mbox_probe(struct platform_device *pdev)
> +{
> +	struct xilinx_mbox *mbox;
> +	struct resource	*regs;
> +	struct mbox_chan *chans;
> +	int ret;
> +
> +	mbox = devm_kzalloc(&pdev->dev, sizeof(*mbox), GFP_KERNEL);
> +	if (!mbox)
> +		return -ENOMEM;
> +
> +	/* get clk and enable */
> +	mbox->clk = devm_clk_get(&pdev->dev, "mbox");
> +	if (IS_ERR(mbox->clk)) {
> +		dev_err(&pdev->dev, "Couldn't get clk.\n");
> +		return PTR_ERR(mbox->clk);
> +	}
> +
> +	/* allocated one channel */
> +	chans = devm_kzalloc(&pdev->dev, sizeof(*chans), GFP_KERNEL);
> +	if (!chans)
> +		return -ENOMEM;

You know statically the number of channels (one), so why not just
include the struct mbox_chan in struct xilinx_mbox (admittedly, I'm not
too familiar with the mailbox subsystem's lifetime guarantees).

> +
> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +
> +	mbox->mbox_base = devm_ioremap_resource(&pdev->dev, regs);
> +	if (IS_ERR(mbox->mbox_base))
> +		return PTR_ERR(mbox->mbox_base);
> +
> +	mbox->irq = platform_get_irq(pdev, 0);
> +	/* if irq is present, we can use it, otherwise, poll */
> +	if (mbox->irq > 0) {
> +		mbox->controller.txdone_irq = true;
> +	} else {
> +		dev_info(&pdev->dev, "IRQ not found, fallback to polling.\n");
> +		mbox->controller.txdone_poll = true;
> +		mbox->controller.txpoll_period = MBOX_POLLING_MS;
> +	}
> +
> +	mbox->dev = &pdev->dev;
> +
> +	/* hardware supports only one channel. */
> +	chans[0].con_priv = mbox;
> +	mbox->controller.dev = mbox->dev;
> +	mbox->controller.num_chans = 1;
> +	mbox->controller.chans = chans;
> +	mbox->controller.ops = &xilinx_mbox_ops;
> +
> +	/* prep and enable the clock */
> +	clk_prepare_enable(mbox->clk);

I know you've already moved where clock management has been done once,
but I'm wondering if clock management be done in startup/shutdown
instead of in probe()?

> +	ret = mbox_controller_register(&mbox->controller);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Register mailbox failed\n");
> +		clk_disable_unprepare(mbox->clk);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, mbox);
> +
> +	return 0;
> +}
> +
> +static int xilinx_mbox_remove(struct platform_device *pdev)
> +{
> +	struct xilinx_mbox *mbox = platform_get_drvdata(pdev);
> +
> +	if (!mbox)

How could this happen?

> +		return -EINVAL;
> +
> +	mbox_controller_unregister(&mbox->controller);
> +
> +	clk_disable_unprepare(mbox->clk);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id xilinx_mbox_match[] = {
> +	{ .compatible = "xlnx,mailbox-2.1" },
> +	{ /* sentinel */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, xilinx_mbox_match);
> +
> +static struct platform_driver xilinx_mbox_driver = {
> +	.probe	= xilinx_mbox_probe,
> +	.remove	= xilinx_mbox_remove,
> +	.driver	= {
> +		.name	= DRIVER_NAME,
> +		.of_match_table	= xilinx_mbox_match,
> +	},
> +};
> +
> +module_platform_driver(xilinx_mbox_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Xilinx mailbox specific functions");
> +MODULE_AUTHOR("Moritz Fischer <moritz.fischer@ettus.com>");
> +MODULE_ALIAS("platform:xilinx-mailbox");
> -- 
> 2.4.1
> 
> --
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