Message-ID: <5566AB68.8000108@xilinx.com>
Date:	Thu, 28 May 2015 07:45:12 +0200
From:	Michal Simek <michal.simek@...inx.com>
To:	Moritz Fischer <moritz.fischer@...us.com>,
	<jassisinghbrar@...il.com>
CC:	<linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<michal.simek@...inx.com>, <soren.brinkmann@...inx.com>,
	<akpm@...ux-foundation.org>, <gregkh@...uxfoundation.org>,
	<mchehab@....samsung.com>, <arnd@...db.de>, <joe@...ches.com>,
	<jingoohan1@...il.com>, <devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv2 2/2] mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

On 05/27/2015 08:35 PM, Moritz Fischer wrote:
> 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 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@...us.com>
> ---
>  MAINTAINERS                      |   7 +
>  drivers/mailbox/Kconfig          |   8 +
>  drivers/mailbox/Makefile         |   2 +
>  drivers/mailbox/mailbox-xilinx.c | 349 ++++++++++++++++++++++++++++++++++
>  4 files changed, 366 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f8e0afb..f1f0d10 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -10986,6 +10986,13 @@ M:	John Linn <John.Linn@...inx.com>
>  S:	Maintained
>  F:	drivers/net/ethernet/xilinx/xilinx_axienet*
>  
> +XILINX MAILBOX DRIVER
> +M:	Moritz Fischer <moritz.fischer@...us.com>
> +L:	linux-kernel@...r.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@...site.dk>
>  L:	linux-serial@...r.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..fd1cdf2
> --- /dev/null
> +++ b/drivers/mailbox/mailbox-xilinx.c
> @@ -0,0 +1,349 @@
> +/*
> + * 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);

empty line here please.

> +	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);
> +			goto polling; /* use polling if failed */

This is the problematic path. For case that request_irq failed - you are
using polling mode but in shutdown below mbox_irq > 0 and you will
free_irq not call del_timer_sync.
I understand that you want to be smart here but it should be enough just
to return error here and you are done. But up2you I expect that this
path wasn't tested.


> +		}
> +
> +		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;
> +	}
> +
> +polling:
> +	/* 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) {

look below.

> +		/* 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");
> +	clk_prepare_enable(mbox->clk);

huh you should probably check error first before enabling.
Also if you call enable there, you should also call
clk_disable_unprepare when any error here happen.
Probably make sense to move this clock enabling below.


> +	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)

0 also suggest error - it means here should be just > 0;

> +		mbox->controller.txdone_irq = true;


missing {} around if - look at coding style guide

> +	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;
> +
> +	ret = mbox_controller_register(&mbox->controller);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Register mailbox failed\n");
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, mbox);
> +
> +	return 0;
> +}
> +
> +

remove this one empty line.

> +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@...us.com>");
> +MODULE_ALIAS("platform:xilinx-mailbox");
> 

Thanks,
Michal

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