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Date: Mon, 29 Nov 2021 22:24:25 +0100
From: Luca Ceresoli <luca@...aceresoli.net>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Chanwoo Choi <cw00.choi@...sung.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
Alessandro Zummo <a.zummo@...ertech.it>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
Wim Van Sebroeck <wim@...ux-watchdog.org>,
devicetree@...r.kernel.org, linux-rtc@...r.kernel.org,
linux-watchdog@...r.kernel.org,
Chiwoong Byun <woong.byun@...sung.com>,
Laxman Dewangan <ldewangan@...dia.com>,
Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v4 7/9] watchdog: max77620: add support for the max77714
variant
Hi Guenter,
thanks for you review!
On 29/11/21 16:53, Guenter Roeck wrote:
> On Sat, Nov 20, 2021 at 04:57:05PM +0100, Luca Ceresoli wrote:
>> The MAX77714 is a MFD chip whose watchdog has the same programming
>> procedures as the MAX77620 watchdog, but most register offsets and bit
>> masks are different, as well as some features.
>>
>> Support the MAX77714 watchdog by adding a variant description table holding
>> the differences.
>>
>> All the features implemented by this driver are available on the MAX77714
>> except for the lack of a WDTOFFC bit. Instead of using a "HAS_*" flag we
>> handle this by holding in the cnfg_glbl2_cfg_bits struct field the bits
>> (i.e. the features) to enable in the CNFG_GLBL2 register. These bits differ
>> among the two models. This implementation allows to avoid any conditional
>> code, keeping the execution flow unchanged.
>>
>> Signed-off-by: Luca Ceresoli <luca@...aceresoli.net>
>> ---
>>
>> This patch is new in v4. It replaces v3 patch 7 ("watchdog: max77714: add
>> driver for the watchdog in the MAX77714 PMIC") by adding MAX77714 wdog
>> support to the existing MAX77620 wdog driver instead of adding a new
>> driver. Suggested by Guenter Roeck and Krzysztof Kozlowski.
>> ---
>> drivers/watchdog/Kconfig | 2 +-
>> drivers/watchdog/max77620_wdt.c | 96 +++++++++++++++++++++++++--------
>> 2 files changed, 75 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>> index a6d97f30325a..f920ad271dde 100644
>> --- a/drivers/watchdog/Kconfig
>> +++ b/drivers/watchdog/Kconfig
>> @@ -677,7 +677,7 @@ config MAX63XX_WATCHDOG
>>
>> config MAX77620_WATCHDOG
>> tristate "Maxim Max77620 Watchdog Timer"
>> - depends on MFD_MAX77620 || COMPILE_TEST
>> + depends on MFD_MAX77620 || MFD_MAX77714 || COMPILE_TEST
>> select WATCHDOG_CORE
>> help
>> This is the driver for the Max77620 watchdog timer.
>> diff --git a/drivers/watchdog/max77620_wdt.c b/drivers/watchdog/max77620_wdt.c
>> index be6a53c30002..06b48295fab6 100644
>> --- a/drivers/watchdog/max77620_wdt.c
>> +++ b/drivers/watchdog/max77620_wdt.c
>> @@ -3,8 +3,10 @@
>> * Maxim MAX77620 Watchdog Driver
>> *
>> * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
>> + * Copyright (C) 2021 Luca Ceresoli
>> *
>> * Author: Laxman Dewangan <ldewangan@...dia.com>
>> + * Author: Luca Ceresoli <luca@...aceresoli.net>
>> */
>>
>> #include <linux/err.h>
>> @@ -13,6 +15,7 @@
>> #include <linux/module.h>
>> #include <linux/mod_devicetable.h>
>> #include <linux/mfd/max77620.h>
>> +#include <linux/mfd/max77714.h>
>> #include <linux/platform_device.h>
>> #include <linux/regmap.h>
>> #include <linux/slab.h>
>> @@ -20,17 +23,66 @@
>>
>> static bool nowayout = WATCHDOG_NOWAYOUT;
>>
>> +/**
>> + * struct max77620_variant - Data specific to a chip variant
>> + * @wdt_info: watchdog descriptor
>> + * @reg_onoff_cnfg2: ONOFF_CNFG2 register offset
>> + * @reg_cnfg_glbl2: CNFG_GLBL2 register offset
>> + * @reg_cnfg_glbl3: CNFG_GLBL3 register offset
>> + * @wdtc_mask: WDTC bit mask in CNFG_GLBL3 (=bits to update to ping the watchdog)
>> + * @bit_wd_rst_wk: WD_RST_WK bit offset within ONOFF_CNFG2
>> + * @cnfg_glbl2_cfg_bits: configuration bits to enable in CNFG_GLBL2 register
>> + */
>> +struct max77620_variant {
>> + const struct watchdog_info wdt_info;
>> + u8 reg_onoff_cnfg2;
>> + u8 reg_cnfg_glbl2;
>> + u8 reg_cnfg_glbl3;
>> + u8 wdtc_mask;
>> + u8 bit_wd_rst_wk;
>> + u8 cnfg_glbl2_cfg_bits;
>> +};
>> +
>> struct max77620_wdt {
>> struct device *dev;
>> struct regmap *rmap;
>> + const struct max77620_variant *drv_data;
>> struct watchdog_device wdt_dev;
>> };
>>
>> +static const struct max77620_variant max77620_wdt_data = {
>> + .wdt_info = {
>> + .identity = "max77620-watchdog",
>> + .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
>> + },
>
> That does not have to be, and should not be, part of device specific data,
> just because of the identity string.
Ok, no problem, will fix, but I have two questions.
First, what's the reason? Coding style or a functional difference?
Usually const data is preferred to runtime assignment.
Second: it's not clear how you expect it to be done. Looking into the
kernel it looks like almost all drivers set a constant string. I could
find only one exception, f71808e_wdt:
https://elixir.bootlin.com/linux/v5.16-rc3/source/drivers/watchdog/f71808e_wdt.c#L471
> Either keep the current identity string,
> mark max77620_wdt_info as __ro_after_init and overwrite the identity string
> there during probe
And also remove 'static' I guess. Hm, I don't love this, as above I tend
to prefer static const when possible for file-scoped data.
> or add the structure to max77620_wdt and fill it out there.
Do you mean like the following, untested, kind-of-pseudocode?
struct max77620_wdt {
struct device *dev;
struct regmap *rmap;
const struct max77620_variant *drv_data;
+ struct watchdog_info info; /* not a pointer! */
struct watchdog_device wdt_dev;
};
and then, in probe:
wdt->dev = dev;
wdt->drv_data = (const struct max77620_variant *)id->driver_data;
/* ... assign other wdt fields ... */
+ strlcpy(wdt_dev->info.identity, id->name, \
+ sizeof(wdt_dev->info.identity));
+ wdt_dev->info.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | \
+ WDIOF_MAGICCLOSE;
Finally, what about simply:
static const struct max77620_variant max77620_wdt_data = {
.wdt_info = {
- .identity = "max77620-watchdog",
+ .identity = "max77xxx-watchdog",
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | ...
},
and always use that struct unconditionally? The max63xx_wdt.c driver
seems to do that. Or, if this is an issue for backward compatibility (is
it?), just leave max77620_wdt_data and the .identity field will always
be "max77620-watchdog" even when using a MAX77714.
Thanks for you patience in reading so far.
--
Luca (slightly confused, but very open to learning)
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