linux-kernel - Re: [PATCH v6 3/3] watchdog: mt7621-wdt: avoid ralink architecture dependent code

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Date:   Tue, 14 Feb 2023 04:10:00 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Sergio Paracuellos <sergio.paracuellos@...il.com>,
        linux-watchdog@...r.kernel.org
Cc:     wim@...ux-watchdog.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, matthias.bgg@...il.com,
        arinc.unal@...nc9.com, tsbogend@...ha.franken.de,
        p.zabel@...gutronix.de, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH v6 3/3] watchdog: mt7621-wdt: avoid ralink architecture
 dependent code

On 2/14/23 00:31, Krzysztof Kozlowski wrote:
> On 13/02/2023 21:05, Sergio Paracuellos wrote:
>> MT7621 SoC has a system controller node. Watchdog need to access to reset
>> status register. Ralink architecture and related driver are old and from
>> the beggining they are using some architecture dependent operations for
>> accessing this shared registers through 'asm/mach-ralink/ralink_regs.h'
>> header file. However this is not ideal from a driver perspective which can
>> just access to the system controller registers in an arch independent way
>> using regmap syscon APIs. Update Kconfig accordingly to select new added
>> dependencies and allow driver to be compile tested.
>>
>> Signed-off-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
>> ---
>>   drivers/watchdog/Kconfig      |  4 +++-
>>   drivers/watchdog/mt7621_wdt.c | 18 +++++++++++++-----
>>   2 files changed, 16 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>> index b64bc49c7..cf752ad64 100644
>> --- a/drivers/watchdog/Kconfig
>> +++ b/drivers/watchdog/Kconfig
>> @@ -1865,7 +1865,9 @@ config GXP_WATCHDOG
>>   config MT7621_WDT
>>   	tristate "Mediatek SoC watchdog"
>>   	select WATCHDOG_CORE
>> -	depends on SOC_MT7620 || SOC_MT7621
>> +	select REGMAP_MMIO
>> +	select MFD_SYSCON
>> +	depends on SOC_MT7620 || SOC_MT7621 || COMPILE_TEST
>>   	help
>>   	  Hardware driver for the Mediatek/Ralink MT7621/8 SoC Watchdog Timer.
>>   
>> diff --git a/drivers/watchdog/mt7621_wdt.c b/drivers/watchdog/mt7621_wdt.c
>> index 40fb2c9ba..22e979bdd 100644
>> --- a/drivers/watchdog/mt7621_wdt.c
>> +++ b/drivers/watchdog/mt7621_wdt.c
>> @@ -15,8 +15,8 @@
>>   #include <linux/moduleparam.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/mod_devicetable.h>
>> -
>> -#include <asm/mach-ralink/ralink_regs.h>
>> +#include <linux/mfd/syscon.h>
>> +#include <linux/regmap.h>
>>   
>>   #define SYSC_RSTSTAT			0x38
>>   #define WDT_RST_CAUSE			BIT(1)
>> @@ -34,6 +34,7 @@
>>   struct mt7621_wdt_data {
>>   	void __iomem *base;
>>   	struct reset_control *rst;
>> +	struct regmap *sysc;
>>   	struct watchdog_device wdt;
>>   };
>>   
>> @@ -104,9 +105,12 @@ static int mt7621_wdt_stop(struct watchdog_device *w)
>>   	return 0;
>>   }
>>   
>> -static int mt7621_wdt_bootcause(void)
>> +static int mt7621_wdt_bootcause(struct mt7621_wdt_data *d)
>>   {
>> -	if (rt_sysc_r32(SYSC_RSTSTAT) & WDT_RST_CAUSE)
>> +	u32 val;
>> +
>> +	regmap_read(d->sysc, SYSC_RSTSTAT, &val);
>> +	if (val & WDT_RST_CAUSE)
>>   		return WDIOF_CARDRESET;
>>   
>>   	return 0;
>> @@ -143,6 +147,10 @@ static int mt7621_wdt_probe(struct platform_device *pdev)
>>   	if (!drvdata)
>>   		return -ENOMEM;
>>   
>> +	drvdata->sysc = syscon_regmap_lookup_by_compatible("mediatek,mt7621-sysc");
>> +	if (IS_ERR(drvdata->sysc))
>> +		return PTR_ERR(drvdata->sysc);
> 
> This should be the backup/error path for original code using syscon
> property. Looking up by compatible is really not portable/re-usable.
> 

I really disagree here.

$ git grep syscon_regmap_lookup_by_compatible | wc
      90     326    8940

I have not yet reviewed this code, but I do not accept this argument against it.

Guenter