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

[Sean Wang]

Hi Sean,

Thanks for your effort for code reviewing. I add comments inline. 

On Thu, 2017-01-05 at 17:12 +0000, Sean Young wrote:
> 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.


okay. i will use this instead of this insistent coding.

> > +
> > +/* 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.
> 

I will remove map_name , but keep irq for synchronize_irq call needs.

> > +};
> > +
> > +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.
> 
Uh, this is related to hardware limitation. Maximum number hardware
holds indeed is only 68 edges as you said :( 

For the case, I will try change the logic into that the whole message 
is dropped if no end of message is seen within 68 counts to avoid
wasting CPU for decoding. 
	
> > +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.


okay, i will use devm_rc_register_device to have simplified 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.

Okay, it's great suggestion. I will use sychronize_irq instead of the my
bad one :) 

> > +
> > +	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
> >