Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Sender: Guenter Roeck <groeck7@gmail.com>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        Terry Bowman <terry.bowman@amd.com>
Cc:     linux-watchdog@vger.kernel.org, Jean Delvare <jdelvare@suse.com>,
        linux-i2c <linux-i2c@vger.kernel.org>,
        Wolfram Sang <wsa@kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Robert Richter <rrichter@amd.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@amd.com>,
        Basavaraj Natikar <Basavaraj.Natikar@amd.com>,
        Shyam Sundar S K <Shyam-sundar.S-k@amd.com>,
        Mario Limonciello <Mario.Limonciello@amd.com>
References: <20220118202234.410555-1-terry.bowman@amd.com>
 <20220118202234.410555-3-terry.bowman@amd.com>
 <CAHp75VdBFN+QMJpYDp8ytGGrBKYyjxU8u=Xrn44Lc3UGLPRQOA@mail.gmail.com>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v3 2/4] Watchdog: sp5100_tco: Refactor MMIO base address
 initialization
Message-ID: <b4f66a42-6f25-7e93-2a3b-5d73af39e72e@roeck-us.net>
Date:   Wed, 19 Jan 2022 07:46:52 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.14.0
MIME-Version: 1.0
In-Reply-To: <CAHp75VdBFN+QMJpYDp8ytGGrBKYyjxU8u=Xrn44Lc3UGLPRQOA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 1/19/22 3:53 AM, Andy Shevchenko wrote:
> On Tue, Jan 18, 2022 at 10:23 PM Terry Bowman <terry.bowman@amd.com> 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.
> 
> ...
> 
>> To: Guenter Roeck <linux@roeck-us.net>
>> To: linux-watchdog@vger.kernel.org
>> To: Jean Delvare <jdelvare@suse.com>
>> To: linux-i2c@vger.kernel.org
>> To: Wolfram Sang <wsa@kernel.org>
>> To: Andy Shevchenko <andy.shevchenko@gmail.com>
>> To: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Cc: linux-kernel@vger.kernel.org
>> Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
>> Cc: Robert Richter <rrichter@amd.com>
>> Cc: Thomas Lendacky <thomas.lendacky@amd.com>
> 
> Same comment to all your patches.
> 
> ...
> 
>> +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;
> 
> Not really used variable.
> 
>> +       if (!mmio_addr)
>> +               return -ENOMEM;
>> +
>> +       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);

Talking about line splits, is this one necessary ?

>> +       if (!tco->tcobase) {
>> +               dev_dbg(dev, "MMIO address 0x%08x failed mapping.\n",
>> +                       mmio_addr);
> 
>> +               devm_release_mem_region(dev, mmio_addr,
>> +                                       SP5100_WDT_MEM_MAP_SIZE);
> 
> Why? If it's a short live mapping, do not use devm.
> 

This is not short lived; it is needed by the driver. The release
is an artifact of calling this function twice and ignoring the error
from devm_ioremap() if the first call fails. devm_release_mem_region()
isn't strictly needed but that would result in keeping the memory
region reserved even though it isn't used by the driver.

There is a functional difference to the original code, though.
The failing devm_ioremap() causes the code to try the alternate
address. I am not sure if that really adds value; devm_ioremap()
fails because the system is out of virtual memory, and calling
it again on a different address doesn't seem to add much value.
I preferred the original code, which would only call devm_ioremap()
after successfully reserving a memory region.

>> +               return -ENOMEM;
>> +       }
> 
>> +       dev_info(dev, "Using 0x%08x for watchdog MMIO address\n",
>> +                mmio_addr);
> 
> Unneeded noise.
> 
>> +       return ret;
> 
> On top of above it's a NIH devm_ioremap_resource().
> 

Not sure what NIH means, but if you refer to the lack of
devm_release_mem_region(), again, it isn't short lived.

>> +}
> 
> 
> ...
> 
>> +       int ret = 0;
> 
> Redundant assignment.
> 
> ...
> 
>> +       /* Check MMIO address conflict */
>> +       ret = __sp5100_tco_prepare_base(tco, mmio_addr, dev_name);
> 
>> +
>> +       /* Check alternate MMIO address conflict */
> 
> Unify this with the previous comment.
> 

Why ? It refers to the code below. If that is a single or two comments
is really just POV.

>> +       if (ret)
>> +               ret = __sp5100_tco_prepare_base(tco, alt_mmio_addr,
>> +                                               dev_name);
> 
> ...
> 
>> +               if (alt_mmio_addr & ((SB800_ACPI_MMIO_DECODE_EN |
>> +                                     SB800_ACPI_MMIO_SEL) !=
>> +                                    SB800_ACPI_MMIO_DECODE_EN)) {
> 
> The split looks ugly. Consider to use temporary variables or somehow
> rearrange the condition that it doesn't break in the middle of the one
> logical token.

Split at the &, maybe.

> 
>> +                       alt_mmio_addr &= ~0xFFF;
> 
> Why capital letters?
> 
>> +                       alt_mmio_addr += SB800_PM_WDT_MMIO_OFFSET;
>> +               }
> 
> ...
> 
>> +               if (!(alt_mmio_addr & (((SB800_ACPI_MMIO_DECODE_EN |
>> +                                      SB800_ACPI_MMIO_SEL)) !=
>> +                     SB800_ACPI_MMIO_DECODE_EN))) {
> 
> Ditto.
> 
>> +                       alt_mmio_addr &= ~0xFFF;
> 
> Ditto.
> 
>> +                       alt_mmio_addr += SB800_PM_WDT_MMIO_OFFSET;
> 
> ...
> 
> Okay, I see this is the original code like this... Perhaps it makes
> sense to reshuffle them (indentation-wise) at the same time and
> mention this in the changelog.
> 
> ...
> 
>>          release_region(SP5100_IO_PM_INDEX_REG, SP5100_PM_IOPORTS_SIZE);
> 
> Is it still needed? I have no context to say if devm_iomap() and this
> are not colliding, please double check the correctness.
> 
Not sure I understand. This is the release of the io region reserved with
request_muxed_region() at the beginning of this function. Why would it no
longer be necessary to release that region ?

Guenter