linux-kernel - Re: [PATCH] memory/tegra: Add missing of_node_get() in tegra_emc_find_node_by_ram

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Message-ID: <bdfc94d0-c634-c391-d74b-2104cbf82b22@linaro.org>
Date:   Wed, 22 Jun 2022 08:50:41 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Liang He <windhl@....com>, thierry.reding@...il.com,
        jonathanh@...dia.com
Cc:     linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH] memory/tegra: Add missing of_node_get() in
 tegra_emc_find_node_by_ram_code

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?

Anyway why do you add of_node_get which is not explained here?

> 
> 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@....com>
> ---
>  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