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Message-ID: <a55ca093-d8d1-6821-1cb9-18343c6f1fd0@amd.com>
Date: Tue, 25 Jan 2022 09:18:59 -0600
From: Terry Bowman <Terry.Bowman@....com>
To: Jean Delvare <jdelvare@...e.de>
Cc: linux@...ck-us.net, linux-watchdog@...r.kernel.org,
linux-i2c@...r.kernel.org, wsa@...nel.org,
andy.shevchenko@...il.com, rafael.j.wysocki@...el.com,
linux-kernel@...r.kernel.org, wim@...ux-watchdog.org,
rrichter@....com, thomas.lendacky@....com,
Nehal-bakulchandra.Shah@....com, Basavaraj.Natikar@....com,
Shyam-sundar.S-k@....com, Mario.Limonciello@....com
Subject: Re: [PATCH v3 2/4] Watchdog: sp5100_tco: Refactor MMIO base address
initialization
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.
>
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