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

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Date:   Wed, 19 Jan 2022 13:53:13 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Terry Bowman <terry.bowman@....com>
Cc:     Guenter Roeck <linux@...ck-us.net>, linux-watchdog@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Wolfram Sang <wsa@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Robert Richter <rrichter@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@....com>,
        Basavaraj Natikar <Basavaraj.Natikar@....com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Mario Limonciello <Mario.Limonciello@....com>
Subject: Re: [PATCH v3 2/4] Watchdog: sp5100_tco: Refactor MMIO base address initialization

On Tue, Jan 18, 2022 at 10:23 PM Terry Bowman <terry.bowman@....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@...ck-us.net>
> To: linux-watchdog@...r.kernel.org
> To: Jean Delvare <jdelvare@...e.com>
> To: linux-i2c@...r.kernel.org
> To: Wolfram Sang <wsa@...nel.org>
> To: Andy Shevchenko <andy.shevchenko@...il.com>
> To: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>
> Cc: Robert Richter <rrichter@....com>
> Cc: Thomas Lendacky <thomas.lendacky@....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);
> +       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.

> +               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().

> +}


...

> +       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.

> +       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.

> +                       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.

-- 
With Best Regards,
Andy Shevchenko