Re: [PATCH v3 3/4] clocksource/drivers/timer-vt8500: Prepare for watchdog functionality

On Sun, May 18, 2025 at 5:24 AM kernel test robot [off-list ref] wrote:

Hi Alexey,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 92a09c47464d040866cf2b4cd052bc60555185fb]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexey-Charkov/dt-bindings-timer-via-vt8500-timer-Convert-to-YAML/20250516-025729
base:   92a09c47464d040866cf2b4cd052bc60555185fb
patch link:    https://lore.kernel.org/r/20250515-vt8500-timer-updates-v3-3-2197a1b062bd%40gmail.com
patch subject: [PATCH v3 3/4] clocksource/drivers/timer-vt8500: Prepare for watchdog functionality
config: loongarch-randconfig-r123-20250517 (https://download.01.org/0day-ci/archive/20250518/202505180911.hDevFA1N-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 14.2.0
reproduce: (https://download.01.org/0day-ci/archive/20250518/202505180911.hDevFA1N-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot [off-list ref]
| Closes: https://lore.kernel.org/oe-kbuild-all/202505180911.hDevFA1N-lkp@intel.com/ (local)

sparse warnings: (new ones prefixed by >>)

quoted

quoted

drivers/clocksource/timer-vt8500.c:201:51: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void *platform_data @@     got void [noderef] __iomem *static [assigned] [toplevel] regbase @@

   drivers/clocksource/timer-vt8500.c:201:51: sparse:     expected void *platform_data
   drivers/clocksource/timer-vt8500.c:201:51: sparse:     got void [noderef] __iomem *static [assigned] [toplevel] regbase

vim +201 drivers/clocksource/timer-vt8500.c

   175
   176  /*
   177   * This probe gets called after the timer is already up and running. This will create
   178   * the watchdog device as a child since the registers are shared.
   179   */
   180  static int vt8500_timer_probe(struct platform_device *pdev)
   181  {
   182          struct platform_device *vt8500_watchdog_device;
   183          struct device *dev = &pdev->dev;
   184          int ret;
   185
   186          if (!sys_timer_ch) {
   187                  dev_info(dev, "Not enabling watchdog: only one irq was given");
   188                  return 0;
   189          }
   190
   191          if (!regbase)
   192                  return dev_err_probe(dev, -ENOMEM,
   193                          "Timer not initialized, cannot create watchdog");
   194
   195          vt8500_watchdog_device = platform_device_alloc("vt8500-wdt", -1);
   196          if (!vt8500_watchdog_device)
   197                  return dev_err_probe(dev, -ENOMEM,
   198                          "Failed to allocate vt8500-wdt");
   199
   200          /* Pass the base address as platform data and nothing else */
 > 201          vt8500_watchdog_device->dev.platform_data = regbase;

Frankly, given that this driver only applies to VT8500 (which is ARM
based), the warning appears a bit overzealous. After all, on ARM MMIO
addresses are in the same physical address space as normal memory
addresses, and furthermore this platform_data is never dereferenced
directly anyway.

I could silence the warning either by more aggressive casting or by
wrapping the pointer into some struct, but both of those sound a bit
overreaching. Would appreciate guidance from the list on how to best
approach this.

Best regards,
Alexey