linux-kernel - Re: [PATCH v2 4/9] arm: twr-k70f120m: timer driver for Kinetis SoC

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Message-ID: <alpine.LNX.2.00.1507011330070.11339@localhost.localdomain>
Date:	Wed, 1 Jul 2015 13:44:46 +0200 (CEST)
From:	Paul Osmialowski <pawelo@...g.net.pl>
To:	Arnd Bergmann <arnd@...db.de>
cc:	linux-arm-kernel@...ts.infradead.org,
	Paul Osmialowski <pawelo@...g.net.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Jiri Slaby <jslaby@...e.cz>, Kumar Gala <galak@...eaurora.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Vinod Koul <vinod.koul@...el.com>,
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-serial@...r.kernel.org,
	devicetree@...r.kernel.org, dmaengine@...r.kernel.org,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Sergei Poselenov <sposelenov@...raft.com>,
	Paul Bolle <pebolle@...cali.nl>,
	Jingchang Lu <jingchang.lu@...escale.com>,
	Yuri Tikhonov <yur@...raft.com>,
	Rob Herring <r.herring@...escale.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>,
	Alexander Potashev <aspotashev@...raft.com>,
	Frank Li <Frank.Li@...escale.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Anson Huang <b20788@...escale.com>
Subject: Re: [PATCH v2 4/9] arm: twr-k70f120m: timer driver for Kinetis SoC

Hi Arnd,

Again, thanks for your remarks. I'm attaching timer patch candidate for 
the third iteration.

Following your advices, I've changed following things:

- not abusing aliases (same goes to pinctrl driver)
- ranges for addressing particular timers (no change in code though, it's
   just up to the .dts implementor)
- *_RD and *_WR macros removed; whole this big-endian issue was a mistake,
   I guess I overdid it a bit trying to make my drivers as universal as
   fsl-edma driver...
- *_SET and *_RESET macros removed - they were giving false sense of
   security hiding potential race.

Any comments are welcome.

On Tue, 30 Jun 2015, Arnd Bergmann wrote:

> On Tuesday 30 June 2015 14:27:25 Paul Osmialowski wrote:
>
>> +Example:
>> +
>> +aliases {
>> +	pit0 = &pit0;
>> +	pit1 = &pit1;
>> +	pit2 = &pit2;
>> +	pit3 = &pit3;
>> +};
>> +
>> +pit@...37000 {
>> +	compatible = "fsl,kinetis-pit-timer";
>> +	reg = <0x40037000 0x100>;
>> +	clocks = <&mcg_pclk_gate 5 23>;
>> +	#address-cells = <1>;
>> +	#size-cells = <1>;
>> +	ranges;
>
> All the subnodes seem to fall inside of the device's own register
> area, so I think it would be nicer to use a specific 'ranges'
> property that only translates the registers in question.
>
>>  / {
>> +	aliases {
>> +		pit0 = &pit0;
>> +		pit1 = &pit1;
>> +		pit2 = &pit2;
>> +		pit3 = &pit3;
>> +	};
>> +
>>  	soc {
>> +		pit@...37000 {
>> +			compatible = "fsl,kinetis-pit-timer";
>> +			reg = <0x40037000 0x100>;
>> +			clocks = <&mcg_pclk_gate 5 23>;
>> +			#address-cells = <1>;
>> +			#size-cells = <1>;
>> +			ranges;
>> +
>> +			pit0: timer@...37100 {
>> +				reg = <0x40037100 0x10>;
>> +				interrupts = <68>;
>> +				status = "disabled";
>> +			};
>
> I don't think it's necessary to have both an alias
> and a label here. What do you use the alias for?
>
>> +
>> +#define KINETIS_PITMCR_PTR(base, reg) \
>> +	(&(((struct kinetis_pit_mcr_regs *)(base))->reg))
>> +#define KINETIS_PITMCR_RD(be, base, reg) \
>> +		((be) ? ioread32be(KINETIS_PITMCR_PTR(base, reg)) \
>> +		      : ioread32(KINETIS_PITMCR_PTR(base, reg)))
>> +#define KINETIS_PITMCR_WR(be, base, reg, val) do { \
>> +		if (be) \
>> +			iowrite32be((val), KINETIS_PITMCR_PTR(base, reg)); \
>> +		else \
>> +			iowrite32((val), KINETIS_PITMCR_PTR(base, reg)); \
>> +	} while (0)
>
> These should really be written as inline functions. Can you
> explain why you need to deal with a big-endian version of this
> hardware? Can you configure the endianess of this register block
> and just set it to one of the two at boot time?
>
>> +#define KINETIS_PIT_PTR(base, reg) \
>> +	(&(((struct kinetis_pit_channel_regs *)(base))->reg))
>> +#define KINETIS_PIT_RD(be, base, reg) \
>> +		((be) ? ioread32be(KINETIS_PIT_PTR(base, reg)) \
>> +		      : ioread32(KINETIS_PIT_PTR(base, reg)))
>> +#define KINETIS_PIT_WR(be, base, reg, val) do { \
>> +		if (be) \
>> +			iowrite32be((val), KINETIS_PIT_PTR(base, reg)); \
>> +		else \
>> +			iowrite32((val), KINETIS_PIT_PTR(base, reg)); \
>> +	} while (0)
>> +#define KINETIS_PIT_SET(be, base, reg, mask) \
>> +		KINETIS_PIT_WR(be, base, reg, \
>> +			KINETIS_PIT_RD(be, base, reg) | (mask))
>> +#define KINETIS_PIT_RESET(be, base, reg, mask) \
>> +		KINETIS_PIT_WR(be, base, reg, \
>> +			KINETIS_PIT_RD(be, base, reg) & (~(mask)))
>
>
> Functions again. Also, just pass a pointer to your own data structure
> into the function, instead of the 'be' and 'base' values.
>
> The 'set' and 'reset' functions look like they need a spinlock
> to avoid races.
>
> 	Arnd
>
View attachment "0004-arm-twr-k70f120m-timer-driver-for-Kinetis-SoC.patch" of type "TEXT/x-diff" (12866 bytes)