Re: [PATCH 2/2] media: rc: add driver for IR remote receiver on MT7623 SoC

[Sean Young]

Hi Sean,

Some review comments.

On Fri, Jan 06, 2017 at 12:06:24AM +0800, sean.wang@xxxxxxxxxxxx wrote:
> From: Sean Wang <sean.wang@xxxxxxxxxxxx>
> 
> This patch adds driver for IR controller on
> Mediatek MT7623 SoC. Currently testing successfully
> on NEC and SONY remote controller only but it should
> work on others (lirc, rc-5 and rc-6).
> 
> Signed-off-by: Sean Wang <sean.wang@xxxxxxxxxxxx>
> ---
>  drivers/media/rc/Kconfig   |  10 ++
>  drivers/media/rc/Makefile  |   1 +
>  drivers/media/rc/mtk-cir.c | 319 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 330 insertions(+)
>  create mode 100644 linux-4.8.rc1_p0/drivers/media/rc/mtk-cir.c
> 
> diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
> index 370e16e..626c500 100644
> --- a/drivers/media/rc/Kconfig
> +++ b/drivers/media/rc/Kconfig
> @@ -389,4 +389,14 @@ config IR_SUNXI
>  	   To compile this driver as a module, choose M here: the module will
>  	   be called sunxi-ir.
>  
> +config IR_MTK
> +	tristate "Mediatek IR remote control"
> +	depends on RC_CORE
> +	depends on ARCH_MEDIATEK || COMPILE_TEST
> +	---help---
> +	   Say Y if you want to use Mediatek internal IR Controller
> +
> +	   To compile this driver as a module, choose M here: the module will
> +	   be called mtk-cir.
> +
>  endif #RC_DEVICES
> diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
> index 379a5c0..505908d 100644
> --- a/drivers/media/rc/Makefile
> +++ b/drivers/media/rc/Makefile
> @@ -37,3 +37,4 @@ obj-$(CONFIG_IR_TTUSBIR) += ttusbir.o
>  obj-$(CONFIG_RC_ST) += st_rc.o
>  obj-$(CONFIG_IR_SUNXI) += sunxi-cir.o
>  obj-$(CONFIG_IR_IMG) += img-ir/
> +obj-$(CONFIG_IR_MTK) += mtk-cir.o
> diff --git a/drivers/media/rc/mtk-cir.c b/drivers/media/rc/mtk-cir.c
> new file mode 100644
> index 0000000..4fa4cab
> --- /dev/null
> +++ b/drivers/media/rc/mtk-cir.c
> @@ -0,0 +1,319 @@
> +/*
> + * Driver for Mediatek MT7623 IR Receiver Controller
> + *
> + * Copyright (C) 2017 Sean Wang <sean.wang@xxxxxxxxxxxx>
> + *
> + * 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; either version 2 of
> + * the License, or (at your option) any later version.
> + *
> + * 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/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/reset.h>
> +#include <media/rc-core.h>
> +
> +#define MTK_IR_DEV "mtk-ir"

KBUILD_MODNAME could be used instead. Currently the module is called
mtk-cir but the rc device will have driver name mtk-ir.

> +
> +/* Register to enable PWM and IR */
> +#define MTK_CONFIG_HIGH_REG       0x0c
> +/* Enable IR pulse width detection */
> +#define MTK_PWM_EN		  BIT(13)
> +/* Enable IR hardware function */
> +#define MTK_IR_EN		  BIT(0)
> +
> +/* Register to setting sample period */
> +#define MTK_CONFIG_LOW_REG        0x10
> +/* Field to set sample period */
> +#define CHK_PERIOD		  0xC00
> +#define MTK_CHK_PERIOD            (((CHK_PERIOD) << 8) & (GENMASK(20, 8)))
> +#define MTK_CHK_PERIOD_MASK	  (GENMASK(20, 8))
> +
> +/* Register to clear state of state machine */
> +#define MTK_IRCLR_REG             0x20
> +/* Bit to restart IR receiving */
> +#define MTK_IRCLR		  BIT(0)
> +
> +/* Register containing pulse width data */
> +#define MTK_CHKDATA_REG(i)        (0x88 + 4 * i)
> +
> +/* Register to enable IR interrupt */
> +#define MTK_IRINT_EN_REG          0xcc
> +/* Bit to enable interrupt */
> +#define MTK_IRINT_EN		  BIT(0)
> +
> +/* Register to ack IR interrupt */
> +#define MTK_IRINT_CLR_REG         0xd0
> +/* Bit to clear interrupt status */
> +#define MTK_IRINT_CLR		  BIT(0)
> +
> +/* Number of registers to record the pulse width */
> +#define MTK_CHKDATA_SZ		  17
> +/* Required frequency */
> +#define MTK_IR_BASE_CLK		  273000000
> +/* Frequency after IR internal divider */
> +#define MTK_IR_CLK		  (MTK_IR_BASE_CLK / 4)
> +/* Sample period in ns */
> +#define MTK_IR_SAMPLE		  (((1000000000ul / MTK_IR_CLK) * CHK_PERIOD))
> +/* Indicate the end of IR data*/
> +#define MTK_IR_END(v)		  (v == 0xff)
> +
> +/* struct mtk_ir -	This is the main datasructure for holding the state
> + *			of the driver
> + * @dev:		The device pointer
> + * @ir_lock:		Make sure that synchronization between remove and ISR
> + * @rc:			The rc instrance
> + * @base:		The mapped register i/o base
> + * @irq:		The IRQ that we are using
> + * @clk:		The clock that we are using
> + * @map_name:		The name for keymap lookup
> + */
> +struct mtk_ir {
> +	struct device   *dev;
> +	/*Protect concurrency between driver removal and ISR*/
> +	spinlock_t      ir_lock;
> +	struct rc_dev   *rc;
> +	void __iomem    *base;
> +	int             irq;
> +	struct clk      *clk;
> +	const char      *map_name;

irq and map_name don't need to be stored here, they're only used in 
mtk_ir_probe.

> +};
> +
> +static void mtk_w32_mask(struct mtk_ir *ir, u32 val, u32 mask, unsigned int reg)
> +{
> +	u32 tmp;
> +
> +	tmp = __raw_readl(ir->base + reg);
> +	tmp = (tmp & ~mask) | val;
> +	__raw_writel(tmp, ir->base + reg);
> +}
> +
> +static void mtk_w32(struct mtk_ir *ir, u32 val, unsigned int reg)
> +{
> +	__raw_writel(val, ir->base + reg);
> +}
> +
> +static u32 mtk_r32(struct mtk_ir *ir, unsigned int reg)
> +{
> +	return __raw_readl(ir->base + reg);
> +}
> +
> +static inline void mtk_irq_disable(struct mtk_ir *ir, u32 mask)
> +{
> +	u32 val;
> +
> +	val = mtk_r32(ir, MTK_IRINT_EN_REG);
> +	mtk_w32(ir, val & ~mask, MTK_IRINT_EN_REG);
> +}
> +
> +static inline void mtk_irq_enable(struct mtk_ir *ir, u32 mask)
> +{
> +	u32 val;
> +
> +	val = mtk_r32(ir, MTK_IRINT_EN_REG);
> +	mtk_w32(ir, val | mask, MTK_IRINT_EN_REG);
> +}
> +
> +static irqreturn_t mtk_ir_irq(int irqno, void *dev_id)
> +{
> +	struct mtk_ir *ir = dev_id;
> +	u8  wid = 0;
> +	u32 i, j, val;
> +	DEFINE_IR_RAW_EVENT(rawir);
> +
> +	spin_lock(&ir->ir_lock);
> +
> +	mtk_irq_disable(ir, MTK_IRINT_EN);
> +
> +	/* Reset decoder state machine */
> +	ir_raw_event_reset(ir->rc);
> +
> +	/* First message must be pulse */
> +	rawir.pulse = false;
> +
> +	/* Handle pulse and space until end of message */
> +	for (i = 0 ; i < MTK_CHKDATA_SZ ; i++) {
> +		val = mtk_r32(ir, MTK_CHKDATA_REG(i));
> +		dev_dbg(ir->dev, "@reg%d=0x%08x\n", i, val);
> +
> +		for (j = 0 ; j < 4 ; j++) {
> +			wid = (val & (0xff << j * 8)) >> j * 8;
> +			rawir.pulse = !rawir.pulse;
> +			rawir.duration = wid * (MTK_IR_SAMPLE + 1);
> +			ir_raw_event_store_with_filter(ir->rc, &rawir);
> +
> +			if (MTK_IR_END(wid))
> +				goto end_msg;
> +		}
> +	}

If I read this correctly, there is a maximum of 17 * 4 = 68 edges per
IR message. The rc6 mce key 0 (scancode 0x800f0400) is 69 edges, so that
won't work.

> +end_msg:
> +	/* Restart the next receive */
> +	mtk_w32_mask(ir, 0x1, MTK_IRCLR, MTK_IRCLR_REG);
> +
> +	ir_raw_event_set_idle(ir->rc, true);
> +	ir_raw_event_handle(ir->rc);
> +
> +	/* Clear interrupt status */
> +	mtk_w32_mask(ir, 0x1, MTK_IRINT_CLR, MTK_IRINT_CLR_REG);
> +
> +	/* Enable interrupt */
> +	mtk_irq_enable(ir, MTK_IRINT_EN);
> +
> +	spin_unlock(&ir->ir_lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int mtk_ir_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *dn = dev->of_node;
> +	struct resource *res;
> +	struct mtk_ir *ir;
> +	u32 val;
> +	int ret = 0;
> +
> +	ir = devm_kzalloc(dev, sizeof(struct mtk_ir), GFP_KERNEL);
> +	if (!ir)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&ir->ir_lock);
> +
> +	ir->dev = dev;
> +
> +	if (!of_device_is_compatible(dn, "mediatek,mt7623-ir"))
> +		return -ENODEV;
> +
> +	ir->clk = devm_clk_get(dev, "clk");
> +	if (IS_ERR(ir->clk)) {
> +		dev_err(dev, "failed to get a ir clock.\n");
> +		return PTR_ERR(ir->clk);
> +	}
> +
> +	if (clk_prepare_enable(ir->clk)) {
> +		dev_err(dev, "try to enable ir_clk failed\n");
> +		ret = -EINVAL;
> +		goto exit_clkdisable_clk;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	ir->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(ir->base)) {
> +		dev_err(dev, "failed to map registers\n");
> +		ret = PTR_ERR(ir->base);
> +		goto exit_clkdisable_clk;
> +	}
> +
> +	ir->rc = rc_allocate_device();
> +	if (!ir->rc) {
> +		dev_err(dev, "failed to allocate device\n");
> +		ret = -ENOMEM;
> +		goto exit_clkdisable_clk;
> +	}
> +
> +	ir->rc->priv = ir;
> +	ir->rc->input_name = MTK_IR_DEV;
> +	ir->rc->input_phys = "mtk-ir/input0";
> +	ir->rc->input_id.bustype = BUS_HOST;
> +	ir->rc->input_id.vendor = 0x0001;
> +	ir->rc->input_id.product = 0x0001;
> +	ir->rc->input_id.version = 0x0001;
> +	ir->map_name = of_get_property(dn, "linux,rc-map-name", NULL);
> +	ir->rc->map_name = ir->map_name ?: RC_MAP_EMPTY;
> +	ir->rc->dev.parent = dev;
> +	ir->rc->driver_type = RC_DRIVER_IR_RAW;
> +	ir->rc->driver_name = MTK_IR_DEV;
> +	ir->rc->allowed_protocols = RC_BIT_ALL;
> +	ir->rc->rx_resolution = MTK_IR_SAMPLE;
> +
> +	ret = rc_register_device(ir->rc);
> +	if (ret) {
> +		dev_err(dev, "failed to register rc device\n");
> +		goto exit_free_dev;
> +	}
> +
> +	platform_set_drvdata(pdev, ir);
> +
> +	ir->irq = platform_get_irq(pdev, 0);
> +	if (ir->irq < 0) {
> +		dev_err(dev, "no irq resource\n");
> +		ret = ir->irq;

>From here on onwards the errors paths should call rc_unregister_device(),
and no longer call rc_free_device(). Note that current master has
devm_rc_allocate_device() and devm_rc_register_device() which would
simplify this code.

> +		goto exit_free_dev;
> +	}
> +
> +	ret = devm_request_irq(dev, ir->irq, mtk_ir_irq, 0, MTK_IR_DEV, ir);
> +	if (ret) {
> +		dev_err(dev, "failed request irq\n");
> +		goto exit_free_dev;
> +	}
> +
> +	mtk_irq_disable(ir, MTK_IRINT_EN);
> +
> +	val = mtk_r32(ir, MTK_CONFIG_HIGH_REG);
> +	val |= MTK_PWM_EN | MTK_IR_EN;
> +	mtk_w32(ir, val, MTK_CONFIG_HIGH_REG);
> +
> +	/* Setting sample period */
> +	mtk_w32_mask(ir, MTK_CHK_PERIOD, MTK_CHK_PERIOD_MASK,
> +		     MTK_CONFIG_LOW_REG);
> +
> +	mtk_irq_enable(ir, MTK_IRINT_EN);
> +
> +	dev_info(dev, "initialized MT7623 IR driver\n");
> +	return 0;
> +
> +exit_free_dev:
> +	rc_free_device(ir->rc);
> +exit_clkdisable_clk:
> +	clk_disable_unprepare(ir->clk);
> +
> +	return ret;
> +}
> +
> +static int mtk_ir_remove(struct platform_device *pdev)
> +{
> +	unsigned long flags;
> +
> +	struct mtk_ir *ir = platform_get_drvdata(pdev);
> +
> +	spin_lock_irqsave(&ir->ir_lock, flags);
> +
> +	mtk_irq_disable(ir, MTK_IRINT_EN);
> +
> +	clk_disable_unprepare(ir->clk);
> +
> +	spin_unlock_irqrestore(&ir->ir_lock, flags);

I'm not convinced the ir_lock is helping to prevent any race condition. An
irq might still already have occurred which will now try to use ir->rc 
which is freed. You can remove the spinlock completely and call 
sychronize_irq() after disabling the mtk interrupt. That way you're sure
the remove is safe to complete.

> +
> +	rc_unregister_device(ir->rc);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id mtk_ir_match[] = {
> +	{ .compatible = "mediatek,mt7623-ir" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, mtk_ir_match);
> +
> +static struct platform_driver mtk_ir_driver = {
> +	.probe          = mtk_ir_probe,
> +	.remove         = mtk_ir_remove,
> +	.driver = {
> +		.name = MTK_IR_DEV,
> +		.of_match_table = mtk_ir_match,
> +	},
> +};
> +
> +module_platform_driver(mtk_ir_driver);
> +
> +MODULE_DESCRIPTION("Mediatek MT7623 IR Receiver Controller Driver");
> +MODULE_AUTHOR("Sean Wang <sean.wang@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> -- 
> 1.9.1
>