On 18 December 2017 at 20:44, Arnd Bergmann [off-list ref] wrote:

On Mon, Dec 18, 2017 at 7:54 AM, Baolin Wang [off-list ref] wrote:

quoted

On 15 December 2017 at 21:13, Arnd Bergmann [off-list ref] wrote:

quoted

On Fri, Dec 15, 2017 at 11:42 AM, Lee Jones [off-list ref] wrote:

quoted

quoted

@@ -87,6 +88,30 @@ static struct syscon *of_syscon_register(struct device_node *np)
      if (ret)
              reg_io_width = 4;

+     ret = of_hwspin_lock_get_id(np, 0);
+     if (ret > 0) {
+             syscon_config.hwlock_id = ret;
+             syscon_config.hwlock_mode = HWLOCK_IRQSTATE;
+     } else {
+             switch (ret) {
+             case -ENOENT:
+                     /* Ignore missing hwlock, it's optional. */
+                     break;
+             case 0:
+                     /* In case of the HWSPINLOCK is not enabled. */
+                     if (!IS_ENABLED(CONFIG_HWSPINLOCK))
+                             break;
+
+                     ret = -EINVAL;
+                     /* fall-through */
+             default:
+                     pr_err("Failed to retrieve valid hwlock: %d\n", ret);
+                     /* fall-through */
+             case -EPROBE_DEFER:
+                     goto err_regmap;
+             }

The 'case 0' seems odd here, are we sure that this is always a failure?
From the of_hwspin_lock_get_id() definition it looks like zero might
be valid, and the !CONFIG_HWSPINLOCK implementation appears
to be written so that we should consider '0' valid but unused and
silently continue with that. If that is generally not the intended
use, it should probably return -EINVAL or something like that.

Yes, 0 is valid for of_hwspin_lock_get_id(), but if we pass 'hwlock id
= 0' to regmap, the regmap core will not regard it as a valid hwlock
id to request the hwlock and will use default mutex lock instead of
hwlock, which will cause problems. Meanwhile if we silently continue
with case 0, users will not realize that they set one invalid hwlock
id to regmap core, so here we regarded case 0 as one invalid id to
print error messages for users.

Something else still seems wrong then: If regmap doesn't accept a zero
lock-id, then of_hwspin_lock_get_id() should never return that as a
valid ID, right?

Um, why regmap doesn't accept a zero lock-id, that because regmap will
reguest hwlock depending on the 'regmap_config->hwlock_id' is not
zero, if regmap regard a zero lock-id as valid which will affect other
'struct regmap_config' definition. So users should not assign the zero
lock-id to regmap.

Now of_hwspin_lock_get_id() can return 0 as valid, which depend on
what is the base id registered by hwspinlock driver. So you think we
should not regard 0 as valid from of_hwspin_lock_get_id(), I can try
to send another patch to fix.

But for this patch I still think we need regard the zero lock-id as
invalid and gave error messages to users.

-- 
Baolin.wang
Best Regards
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