Re: [PATCH v3 2/4] Watchdog: sp5100_tco: Refactor MMIO base address initialization

[Terry Bowman <Terry.Bowman@amd.com>]

On 1/25/22 7:45 AM, Jean Delvare wrote:
> Hi Terry,
> 
> Sorry for the late review, I hope you did not send an updated series
> already.
> 

Hi Jean,

No problem. I have not sent another revision yet. I'll add your requested 
changes in the next revision.

> On Tue, 18 Jan 2022 14:22:32 -0600, Terry Bowman wrote:
>> Combine MMIO base address and alternate base address detection. Combine
>> based on layout type. This will simplify the function by eliminating
>> a switch case.
>>
>> Move existing request/release code into functions. This currently only
>> supports port I/O request/release. The move into a separate function
>> will make it ready for adding MMIO region support.
>>
>> (...)
>> +static int __sp5100_tco_prepare_base(struct sp5100_tco *tco,
>> +				     u32 mmio_addr,
>> +				     const char *dev_name)
>> +{
>> +	struct device *dev = tco->wdd.parent;
>> +	int ret = 0;
>> +
>> +	if (!mmio_addr)
>> +		return -ENOMEM;
> 
> Can this actually happen? If it does, is -ENOMEM really the best error
> value?
> 

This can happen if mmio_addr is not assigned in sp5100_tco_setupdevice_mmio() 
before calling sp5100_tco_prepare_base() and __sp5100_tco_prepare_base().

I can move the NULL check out of __sp5100_tco_prepare_base() and into
sp5100_tco_prepare_base() before calling __sp5100_tco_prepare_base().
As you describe below.

The ENOMEM return value should be interpreted as the mmio_addr is not 
available. EBUSY does not describe the failure correctly because EBUSY 
implies the resource is present and normally available but not available 
at this time. Do you have a return value preference ?

> And if it can happen, I think I would prefer if you would simply not
> call this function, knowing it can only fail. In other words, I'd go
> for something like the following in the function below:
> 
> 	/* Check MMIO address conflict */
> 	if (mmio_addr)
> 		ret = __sp5100_tco_prepare_base(tco, mmio_addr, dev_name);
> 
> The intention is clearer and execution is faster too.
> 
Ok

>> +
>> +	if (!devm_request_mem_region(dev, mmio_addr,
>> +				    SP5100_WDT_MEM_MAP_SIZE,
>> +				    dev_name)) {
>> +		dev_dbg(dev, "MMIO address 0x%08x already in use\n",
>> +			mmio_addr);
>> +		return -EBUSY;
>> +	}
>> +
>> +	tco->tcobase = devm_ioremap(dev, mmio_addr,
>> +				    SP5100_WDT_MEM_MAP_SIZE);
>> +	if (!tco->tcobase) {
>> +		dev_dbg(dev, "MMIO address 0x%08x failed mapping.\n",
>> +			mmio_addr);
> 
> Remove trailing dot for consistency with the other messages.
> 

Ok.

>> +		devm_release_mem_region(dev, mmio_addr,
>> +					SP5100_WDT_MEM_MAP_SIZE);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	dev_info(dev, "Using 0x%08x for watchdog MMIO address\n",
>> +		 mmio_addr);
>> +
>> +	return ret;
>> +}
>> +
>> +static int sp5100_tco_prepare_base(struct sp5100_tco *tco,
>> +				   u32 mmio_addr,
>> +				   u32 alt_mmio_addr,
>> +				   const char *dev_name)
>> +{
>> +	struct device *dev = tco->wdd.parent;
>> +	int ret = 0;
>> +
>> +	dev_dbg(dev, "Got 0x%08x from SBResource_MMIO register\n",
>> +		mmio_addr);
>> +
>> +	/* Check MMIO address conflict */
>> +	ret = __sp5100_tco_prepare_base(tco, mmio_addr, dev_name);
>> +
>> +	/* Check alternate MMIO address conflict */
>> +	if (ret)
>> +		ret = __sp5100_tco_prepare_base(tco, alt_mmio_addr,
>> +						dev_name);
>> +
>> +	if (ret)
>> +		dev_err(dev, "Failed to reserve-map MMIO (%X) and alternate MMIO (%X) regions. ret=%X",
>> +			mmio_addr, alt_mmio_addr, ret);
> 
> Format for the addresses is inconsistent with the other messages above,
> please use 0x%08x for consistency. As for the return value (which
> should be preceded by a comma rather than a dot), it should be printed
> as a decimal, not hexadecimal, value.
> 

Ok, I'll correct the address format to use '0x', change the period to a comma,
and display the the return code as decimal.

> (And nitpicking: I'd split after "dev," so as to not make the line
> longer than needed.
> 

I'll move the line break at 'dev,'.

>> +
>> +	return ret;
>> +}
>> +
>>  static int sp5100_tco_timer_init(struct sp5100_tco *tco)
>>  {
>>  	struct watchdog_device *wdd = &tco->wdd;
>> @@ -264,6 +324,7 @@ static int sp5100_tco_setupdevice(struct device *dev,
>>  	struct sp5100_tco *tco = watchdog_get_drvdata(wdd);
>>  	const char *dev_name;
>>  	u32 mmio_addr = 0, val;
>> +	u32 alt_mmio_addr = 0;
>>  	int ret;
>>  
>>  	/* Request the IO ports used by this driver */
>> @@ -282,11 +343,35 @@ static int sp5100_tco_setupdevice(struct device *dev,
>>  		dev_name = SP5100_DEVNAME;
>>  		mmio_addr = sp5100_tco_read_pm_reg32(SP5100_PM_WATCHDOG_BASE) &
>>  								0xfffffff8;
>> +
>> +		/*
>> +		 * Secondly, Find the watchdog timer MMIO address
>> +		 * from SBResource_MMIO register.
>> +		 */
>> +		/* Read SBResource_MMIO from PCI config(PCI_Reg: 9Ch) */
>> +		pci_read_config_dword(sp5100_tco_pci,
>> +				      SP5100_SB_RESOURCE_MMIO_BASE,
>> +				      &alt_mmio_addr);
>> +		if (alt_mmio_addr & ((SB800_ACPI_MMIO_DECODE_EN |
>> +				      SB800_ACPI_MMIO_SEL) !=
>> +				     SB800_ACPI_MMIO_DECODE_EN)) {
>> +			alt_mmio_addr &= ~0xFFF;
>> +			alt_mmio_addr += SB800_PM_WDT_MMIO_OFFSET;
>> +		}
>>  		break;
>>  	case sb800:
>>  		dev_name = SB800_DEVNAME;
>>  		mmio_addr = sp5100_tco_read_pm_reg32(SB800_PM_WATCHDOG_BASE) &
>>  								0xfffffff8;
>> +		/* Read SBResource_MMIO from AcpiMmioEn(PM_Reg: 24h) */
>> +		alt_mmio_addr =
>> +			sp5100_tco_read_pm_reg32(SB800_PM_ACPI_MMIO_EN);
>> +		if (!(alt_mmio_addr & (((SB800_ACPI_MMIO_DECODE_EN |
>> +				       SB800_ACPI_MMIO_SEL)) !=
>> +		      SB800_ACPI_MMIO_DECODE_EN))) {
> 
> The condition is the opposite of the sp5100 case above, which looks
> quite suspicious. As far as I can see, that wasn't the case in the
> original code. Please double check. In any case, please avoid double
> negations, they are too easy to get wrong.
> 

Yes, I found this earlier. I have fix for this in the next revision.

>> +			alt_mmio_addr &= ~0xFFF;
>> +			alt_mmio_addr += SB800_PM_WDT_MMIO_OFFSET;
>> +		}
>>  		break;
>>  	case efch:
>>  		dev_name = SB800_DEVNAME;
>> @@ -305,87 +390,24 @@ static int sp5100_tco_setupdevice(struct device *dev,
>>  		val = sp5100_tco_read_pm_reg8(EFCH_PM_DECODEEN);
>>  		if (val & EFCH_PM_DECODEEN_WDT_TMREN)
>>  			mmio_addr = EFCH_PM_WDT_ADDR;
>> +
>> +		val = sp5100_tco_read_pm_reg8(EFCH_PM_ISACONTROL);
>> +		if (val & EFCH_PM_ISACONTROL_MMIOEN)
>> +			alt_mmio_addr = EFCH_PM_ACPI_MMIO_ADDR +
>> +				EFCH_PM_ACPI_MMIO_WDT_OFFSET;
>>  		break;
>>  	default:
>>  		return -ENODEV;
>>  	}
>> (...)
> 
> Rest looks OK to me.
>