[PATCH v3 1/2] watchdog: NXP LPC18xx Watchdog Timer Driver

Fri Jul 24 13:57:46 PDT 2015

El 24/07/15 a las 11:04, Guenter Roeck escibió:
> On 07/24/2015 06:54 AM, Ariel D'Alessandro wrote:
>>
>>
>> El 23/07/15 a las 18:21, Guenter Roeck escibió:
>>> On 07/23/2015 01:38 PM, Ariel D'Alessandro wrote:
>>>> Hi Guenter,
>>>>
>>>> El 21/07/15 a las 21:51, Guenter Roeck escibió:
>>>>> On 07/14/2015 05:50 PM, Ariel D'Alessandro wrote:
>>>>>> This commit adds support for the watchdog timer found in NXP LPC SoCs
>>>>>> family, which includes LPC18xx/LPC43xx. Other SoCs in that family may
>>>>>> share the same watchdog hardware.
>>>>>>
>>>>>> Watchdog driver registers a restart handler that will restart the
>>>>>> system
>>>>>> by performing an incorrect feed after ensuring the watchdog is
>>>>>> enabled in
>>>>>> reset mode.
>>>>>>
>>>>>> As watchdog cannot be disabled in hardware, driver's stop routine
>>>>>> will
>>>>>> regularly send a keepalive ping using a timer.
>>>>>>
>>>>>> Signed-off-by: Ariel D'Alessandro <ariel at vanguardiasur.com.ar>
>>>>>
>>>>> Hi Ariel,
>>>>>
>>>>> sorry for the delayed response. Comments below.
>>>>>
>>>>> Guenter
>>>>>
>>>>>> ---
>>>>>>     drivers/watchdog/Kconfig       |  11 ++
>>>>>>     drivers/watchdog/Makefile      |   1 +
>>>>>>     drivers/watchdog/lpc18xx_wdt.c | 344
>>>>>> +++++++++++++++++++++++++++++++++++++++++
>>>>>>     3 files changed, 356 insertions(+)
>>>>>>     create mode 100644 drivers/watchdog/lpc18xx_wdt.c
>>>>>>
>>>>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>>>>> index 742fbbc..af5e2e3 100644
>>>>>> --- a/drivers/watchdog/Kconfig
>>>>>> +++ b/drivers/watchdog/Kconfig
>>>>>> @@ -547,6 +547,17 @@ config DIGICOLOR_WATCHDOG
>>>>>>           To compile this driver as a module, choose M here: the
>>>>>>           module will be called digicolor_wdt.
>>>>>>
>>>>>> +config LPC18XX_WATCHDOG
>>>>>> +    tristate "LPC18xx/43xx Watchdog"
>>>>>> +    depends on ARCH_LPC18XX || COMPILE_TEST
>>>>>> +    select WATCHDOG_CORE
>>>>>> +    help
>>>>>> +      Say Y here if to include support for the watchdog timer
>>>>>> +      in NXP LPC SoCs family, which includes LPC18xx/LPC43xx
>>>>>> +      processors.
>>>>>> +      To compile this driver as a module, choose M here: the
>>>>>> +      module will be called lpc18xx_wdt.
>>>>>> +
>>>>>>     # AVR32 Architecture
>>>>>>
>>>>>>     config AT32AP700X_WDT
>>>>>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
>>>>>> index 59ea9a1..1b0ef48 100644
>>>>>> --- a/drivers/watchdog/Makefile
>>>>>> +++ b/drivers/watchdog/Makefile
>>>>>> @@ -66,6 +66,7 @@ obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
>>>>>>     obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
>>>>>>     obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
>>>>>>     obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
>>>>>> +obj-$(CONFIG_LPC18XX_WATCHDOG) += lpc18xx_wdt.o
>>>>>>
>>>>>>     # AVR32 Architecture
>>>>>>     obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
>>>>>> diff --git a/drivers/watchdog/lpc18xx_wdt.c
>>>>>> b/drivers/watchdog/lpc18xx_wdt.c
>>>>>> new file mode 100644
>>>>>> index 0000000..2b489fc
>>>>>> --- /dev/null
>>>>>> +++ b/drivers/watchdog/lpc18xx_wdt.c
>>>>>> @@ -0,0 +1,344 @@
>>>>>> +/*
>>>>>> + * NXP LPC18xx Watchdog Timer (WDT)
>>>>>> + *
>>>>>> + * Copyright (c) 2015 Ariel D'Alessandro <ariel at vanguardiasur.com>
>>>>>> + *
>>>>>> + * This program is free software; you can redistribute it and/or
>>>>>> modify it
>>>>>> + * under the terms of the GNU General Public License version 2 as
>>>>>> published by
>>>>>> + * the Free Software Foundation.
>>>>>> + *
>>>>>> + * Notes
>>>>>> + * -----
>>>>>> + * The Watchdog consists of a fixed divide-by-4 clock pre-scaler and
>>>>>> a 24-bit
>>>>>> + * counter which decrements on every clock cycle.
>>>>>> + *
>>>>>> + */
>>>>>> +
>>>>>> +#include <linux/clk.h>
>>>>>> +#include <linux/io.h>
>>>>>> +#include <linux/module.h>
>>>>>> +#include <linux/of.h>
>>>>>> +#include <linux/platform_device.h>
>>>>>> +#include <linux/reboot.h>
>>>>>> +#include <linux/watchdog.h>
>>>>>> +
>>>>>> +/* Registers */
>>>>>> +#define LPC18XX_WDT_MOD            0x00
>>>>>> +#define LPC18XX_WDT_MOD_WDEN        BIT(0)
>>>>>> +#define LPC18XX_WDT_MOD_WDRESET        BIT(1)
>>>>>> +#define LPC18XX_WDT_MOD_WDTOF_MASK    0x04
>>>>>
>>>>> Not used.
>>>>
>>>> That's right. I'll remove it.
>>>>
>>>>>
>>>>>> +
>>>>>> +#define LPC18XX_WDT_TC            0x04
>>>>>> +#define LPC18XX_WDT_TC_MIN        0xff
>>>>>> +#define LPC18XX_WDT_TC_MAX        0xffffff
>>>>>> +
>>>>>> +#define LPC18XX_WDT_FEED        0x08
>>>>>> +#define LPC18XX_WDT_FEED_MAGIC1        0xaa
>>>>>> +#define LPC18XX_WDT_FEED_MAGIC2        0x55
>>>>>> +
>>>>>> +#define LPC18XX_WDT_TV            0x0c
>>>>>> +
>>>>>> +/* Clock pre-scaler */
>>>>>> +#define LPC18XX_WDT_CLK_DIV        4
>>>>>> +
>>>>>> +/* Timeout values in seconds */
>>>>>> +#define LPC18XX_WDT_DEF_TIMEOUT        5
>>>>>> +
>>>>>
>>>>> This is (still) really low for Linux. Something like min(30,
>>>>> max_timeout)
>>>>> might make more sense.
>>>>
>>>> Remember that hardware limits timeout to a maximum value of 5.
>>>>
>>>> As you said before we could use a soft timer, but I not sure that's a
>>>> good idea. As Ezequiel said [0], it might be adding bloat and we must
>>>> consider that this watchdog controller is included in cortex-M MCUs.
>>>>
>>>> [0] http://www.spinics.net/lists/linux-watchdog/msg06904.html
>>>>
>>>
>>> Further down you have
>>>      lpc18xx_wdt->wdt_dev.max_timeout = (LPC18XX_WDT_TC_MAX *
>>>                            LPC18XX_WDT_CLK_DIV) / clk_rate;
>>>
>>> which seems to contradict this statement. If the maximum timeout is 5
>>> seconds,
>>> why don't you set max_timeout to a fixed value of 5 seconds ?
>>
>> Well, I think that's the less hardcoded way. It might allow the driver
>> to be extended to another HW variant that configures the wdt clk rate.
>>
>> I see what's your point. As you proposed, using the same criterion I
>> should do this:
>>
>> #define LPC18XX_WDT_DEF_TIMEOUT         (unsigned int)30
>>
>> and further down, in probe function:
>>
>> lpc18xx_wdt->wdt_dev.timeout = min(LPC18XX_WDT_DEF_TIMEOUT,
>>                    lpc18xx_wdt->wdt_dev.max_timeout);
>>
>> Is this close enough to your solution?
>>
> Yes, but why the typecast for LPC18XX_WDT_DEF_TIMEOUT ?
> 

Otherwise the compiler will warn about a comparison of distinct pointer
types in expansion of the macro 'min'.

Should it be casted when using it better than in definition?