At 2022-06-22 14:50:41, "Krzysztof Kozlowski" <krzysztof.kozlowski@xxxxxxxxxx> wrote: >On 22/06/2022 06:28, Liang He wrote: >> of_find_node_by_name() will decrease the refcount of its first arg and >> we need to add a of_node_put() to keep refcount balance. > >We do NOT need to add an of_node_put? > Sorry, this is a typo, I want to say we need to add a 'of_node_get()' >Anyway why do you add of_node_get which is not explained here? > This is a common mistake that missing the of_node_get(X) before we call of_find_node_by_name(X,..) as the of_find_xxx will decrease the refcount of X. A similar error is: https://lore.kernel.org/all/20200720152806.443262648@xxxxxxxxxxxxxxxxxxx/ If I am wrong, please correct me, thanks. >> >> Besides, during the 'for' loop execution, the refcount of 'np' will be >> automatically increased and decreased. There is no need to call >> of_node_put() again. >> >> Signed-off-by: Liang He <windhl@xxxxxxx> >> --- >> drivers/memory/tegra/tegra20-emc.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/memory/tegra/tegra20-emc.c b/drivers/memory/tegra/tegra20-emc.c >> index 25ba3c5e4ad6..e43a5f8e188e 100644 >> --- a/drivers/memory/tegra/tegra20-emc.c >> +++ b/drivers/memory/tegra/tegra20-emc.c >> @@ -477,6 +477,7 @@ tegra_emc_find_node_by_ram_code(struct tegra_emc *emc) >> >> ram_code = tegra_read_ram_code(); >> >> + of_get_node(dev->of_node); >> for (np = of_find_node_by_name(dev->of_node, "emc-tables"); np; >> np = of_find_node_by_name(np, "emc-tables")) { >> err = of_property_read_u32(np, "nvidia,ram-code", &value); >> @@ -484,6 +485,7 @@ tegra_emc_find_node_by_ram_code(struct tegra_emc *emc) >> struct device_node *lpddr2_np; >> bool cfg_mismatches = false; >> >> + of_node_get(np); >> lpddr2_np = of_find_node_by_name(np, "lpddr2"); >> if (lpddr2_np) { >> const struct lpddr2_info *info; >> @@ -521,7 +523,6 @@ tegra_emc_find_node_by_ram_code(struct tegra_emc *emc) >> } >> >> if (cfg_mismatches) { >> - of_node_put(np); >> continue; >> } >> } > > >Best regards, >Krzysztof
