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Date: Mon, 8 Apr 2019 15:53:04 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
David Lechner <david@...hnology.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v4 01/11] clocksource: davinci-timer: new driver
On 08/04/2019 15:49, Bartosz Golaszewski wrote:
> wt., 2 kwi 2019 o 11:21 Daniel Lezcano <daniel.lezcano@...aro.org> napisał(a):
>>
>> On 18/03/2019 13:10, Bartosz Golaszewski wrote:
>>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>
>>> Currently the clocksource and clockevent support for davinci platforms
>>> lives in mach-davinci. It hard-codes many things, uses global variables,
>>> implements functionalities unused by any platform and has code fragments
>>> scattered across many (often unrelated) files.
>>>
>>> Implement a new, modern and simplified timer driver and put it into
>>> drivers/clocksource. We still need to support legacy board files so
>>> export a config structure and a function that allows machine code to
>>> register the timer.
>>>
>>> We don't bother freeing resources on errors in davinci_timer_register()
>>> as the system won't boot without a timer anyway.
>>>
>>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>> Reviewed-by: David Lechner <david@...hnology.com>
>>> ---
>>> drivers/clocksource/Kconfig | 5 +
>>> drivers/clocksource/Makefile | 1 +
>>> drivers/clocksource/timer-davinci.c | 438 ++++++++++++++++++++++++++++
>>> include/clocksource/timer-davinci.h | 44 +++
>>> 4 files changed, 488 insertions(+)
>>> create mode 100644 drivers/clocksource/timer-davinci.c
>>> create mode 100644 include/clocksource/timer-davinci.h
>>>
>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>>> index 171502a356aa..08b1f539cfc4 100644
>>> --- a/drivers/clocksource/Kconfig
>>> +++ b/drivers/clocksource/Kconfig
>>> @@ -42,6 +42,11 @@ config BCM_KONA_TIMER
>>> help
>>> Enables the support for the BCM Kona mobile timer driver.
>>>
>>> +config DAVINCI_TIMER
>>> + bool "Texas Instruments DaVinci timer driver"
>>> + help
>>> + Enables the support for the TI DaVinci timer driver.
>>> +
>>
>> Please make it a silence option only visible with COMPILE_TEST or
>> EXPERT, examples here:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/clocksource/Kconfig#n45
>>
>> or second format:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/clocksource/Kconfig#n459
>>
>>> config DIGICOLOR_TIMER
>>> bool "Digicolor timer driver" if COMPILE_TEST
>>> select CLKSRC_MMIO
>>> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
>>> index be6e0fbc7489..3c73d0e58b45 100644
>>> --- a/drivers/clocksource/Makefile
>>> +++ b/drivers/clocksource/Makefile
>>> @@ -15,6 +15,7 @@ obj-$(CONFIG_SH_TIMER_TMU) += sh_tmu.o
>>> obj-$(CONFIG_EM_TIMER_STI) += em_sti.o
>>> obj-$(CONFIG_CLKBLD_I8253) += i8253.o
>>> obj-$(CONFIG_CLKSRC_MMIO) += mmio.o
>>> +obj-$(CONFIG_DAVINCI_TIMER) += timer-davinci.o
>>> obj-$(CONFIG_DIGICOLOR_TIMER) += timer-digicolor.o
>>> obj-$(CONFIG_OMAP_DM_TIMER) += timer-ti-dm.o
>>> obj-$(CONFIG_DW_APB_TIMER) += dw_apb_timer.o
>>> diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c
>>> new file mode 100644
>>> index 000000000000..46dfc4d457fc
>>> --- /dev/null
>>> +++ b/drivers/clocksource/timer-davinci.c
>>> @@ -0,0 +1,438 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +//
>>> +// TI DaVinci clocksource driver
>>> +//
>>> +// Copyright (C) 2019 Texas Instruments
>>> +// Author: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>> +// (with some parts adopted from code by Kevin Hilman <khilman@...libre.com>)
>>> +#include <linux/clk.h>
>>> +#include <linux/clockchips.h>
>>> +#include <linux/clocksource.h>
>>> +#include <linux/err.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/of_address.h>
>>> +#include <linux/of_irq.h>
>>> +#include <linux/sched_clock.h>
>>> +
>>> +#include <clocksource/timer-davinci.h>
>>> +
>>> +#undef pr_fmt
>>> +#define pr_fmt(fmt) "%s: " fmt "\n", __func__
>>> +
>>> +#define DAVINCI_TIMER_REG_TIM12 0x10
>>> +#define DAVINCI_TIMER_REG_TIM34 0x14
>>> +#define DAVINCI_TIMER_REG_PRD12 0x18
>>> +#define DAVINCI_TIMER_REG_PRD34 0x1c
>>> +#define DAVINCI_TIMER_REG_TCR 0x20
>>> +#define DAVINCI_TIMER_REG_TGCR 0x24
>>> +
>>> +#define DAVINCI_TIMER_TIMMODE_MASK GENMASK(3, 2)
>>> +#define DAVINCI_TIMER_RESET_MASK GENMASK(1, 0)
>>> +#define DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED BIT(2)
>>> +#define DAVINCI_TIMER_UNRESET GENMASK(1, 0)
>>> +
>>> +/* Shift depends on timer. */
>>> +#define DAVINCI_TIMER_ENAMODE_MASK GENMASK(1, 0)
>>> +#define DAVINCI_TIMER_ENAMODE_DISABLED 0x00
>>> +#define DAVINCI_TIMER_ENAMODE_ONESHOT BIT(0)
>>> +#define DAVINCI_TIMER_ENAMODE_PERIODIC BIT(1)
>>> +
>>> +#define DAVINCI_TIMER_ENAMODE_SHIFT_TIM12 6
>>> +#define DAVINCI_TIMER_ENAMODE_SHIFT_TIM34 22
>>> +
>>> +#define DAVINCI_TIMER_MIN_DELTA 0x01
>>> +#define DAVINCI_TIMER_MAX_DELTA 0xfffffffe
>>> +
>>> +#define DAVINCI_TIMER_CLKSRC_BITS 32
>>> +
>>> +#define DAVINCI_TIMER_TGCR_DEFAULT \
>>> + (DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED | DAVINCI_TIMER_UNRESET)
>>> +
>>> +enum {
>>> + DAVINCI_TIMER_MODE_DISABLED = 0,
>>> + DAVINCI_TIMER_MODE_ONESHOT,
>>> + DAVINCI_TIMER_MODE_PERIODIC,
>>> +};
>>> +
>>> +struct davinci_timer_data;
>>> +
>>> +typedef void (*davinci_timer_set_period_func)(struct davinci_timer_data *,
>>> + unsigned int period);
>>> +
>>> +/**
>>> + * struct davinci_timer_regs - timer-specific register offsets
>>> + *
>>> + * @tim_off: timer counter register
>>> + * @prd_off: timer period register
>>> + * @enamode_shift: left bit-shift of the enable register associated
>>> + * with this timer in the TCR register
>>> + */
>>> +struct davinci_timer_regs {
>>> + unsigned int tim_off;
>>> + unsigned int prd_off;
>>> + unsigned int enamode_shift;
>>> +};
>>> +
>>> +struct davinci_timer_data {
>>> + void __iomem *base;
>>> + const struct davinci_timer_regs *regs;
>>> + unsigned int mode;
>>> + davinci_timer_set_period_func set_period;
>>> + unsigned int cmp_off;
>>> +};
>>> +
>>> +struct davinci_timer_clockevent {
>>> + struct clock_event_device dev;
>>> + unsigned int tick_rate;
>>> + struct davinci_timer_data timer;
>>> +};
>>
>> The timer-of API provides the functions and the common structures for
>> the usual operations. Please use them instead of redefining your own
>> structures.
>>
>
> After giving it another thought, I don't think we can use timer-of in
> this driver easily.
>
> It's meant to work both for board files and device-tree. The solution
> with the least code duplication is to take the device_node on DT
> systems and put all relevant properties into the custom structure used
> by board files users. Timer-of maps the memory, enables the clock and
> requests interrupts directly from the device_node. I'd have to do the
> same for board files manually anyway. I think it's better to have a
> single point of entry for the initialization code.
>
> Even if I were just to reuse the timer-of structures without reusing
> the actual code - they are still missing certain fields. We're using
> 32-bit "halves" of timers that are actually 64 bits - the 32-bit
> control register deals with both by using the same layout of bit
> fields but shifted. This is what the struct davinci_timer_regs is for.
> Reusing those structures would also be confusing because of the of_
> prefix in the naming.
>
> I'd prefer to leave it as it is. Let me know what you think.
Sorry for not being responsive, I've been OoO last week. Give me some
days to digest the emails stack I have in my mailbox and I'll tell you
after reviewing how works this timer.
--
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