linux-kernel - Re: [PATCH] memory: tegra210-emc: Support Device Tree EMC Tables

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Message-ID: <0dcf786f-d93a-4526-bdc6-e11d59347f98@kernel.org>
Date: Sun, 4 May 2025 15:37:58 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: webgeek1234@...il.com, Thierry Reding <thierry.reding@...il.com>,
 Jonathan Hunter <jonathanh@...dia.com>
Cc: linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH] memory: tegra210-emc: Support Device Tree EMC Tables

On 30/04/2025 19:52, Aaron Kling via B4 Relay wrote:
> +#undef EMC_READ_PROP
> +#undef EMC_READ_STRING
> +#undef EMC_READ_PROP_ARRAY
> +
> +	return 0;
> +}
> +
> +#define NOMINAL_COMPATIBLE "nvidia,tegra21-emc-table"
> +#define DERATED_COMPATIBLE "nvidia,tegra21-emc-table-derated"

No, you cannot add undocumented compatibles. Missing bindings.

> +static int tegra210_emc_load_timings_from_dt(struct tegra210_emc *emc,
> +					     struct device_node *node)
> +{
> +	struct tegra210_emc_timing *timing;
> +	unsigned int num_nominal = 0, num_derated = 0;
> +	int err;
> +
> +	emc->num_timings = 0;
> +	for_each_child_of_node_scoped(node, child) {
> +		if (of_device_is_compatible(child, NOMINAL_COMPATIBLE))
> +			emc->num_timings++;
> +		else if (of_device_is_compatible(child, DERATED_COMPATIBLE))
> +			num_derated++;
> +	}
> +
> +	if (!emc->num_timings || (num_derated && (emc->num_timings != num_derated)))
> +		return -EINVAL;
> +
> +	emc->nominal = devm_kcalloc(emc->dev, emc->num_timings, sizeof(*timing),
> +				    GFP_KERNEL);
> +	if (!emc->nominal)
> +		return -ENOMEM;
> +
> +	if (num_derated) {
> +		num_derated = 0;
> +		emc->derated = devm_kcalloc(emc->dev, emc->num_timings, sizeof(*timing),
> +					    GFP_KERNEL);
> +		if (!emc->derated)
> +			return -ENOMEM;
> +	}
> +
> +	for_each_child_of_node_scoped(node, child) {
> +		if (of_device_is_compatible(child, NOMINAL_COMPATIBLE))
> +			timing = &emc->nominal[num_nominal++];
> +		else if (of_device_is_compatible(child, DERATED_COMPATIBLE))
> +			timing = &emc->derated[num_derated++];
> +		else
> +			continue;
> +
> +		err = load_one_timing_from_dt(emc, timing, child);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int tegra210_emc_parse_dt(struct tegra210_emc *emc)
> +{
> +	struct device_node *node, *np = emc->dev->of_node;
> +	int ram_code, ret = 0;
> +
> +	if (!np) {
> +		dev_err(emc->dev, "Unable to find emc node\n");
> +		return -ENODEV;
> +	}
> +
> +	if (of_find_property(np, "nvidia,use-ram-code", NULL)) {

I cannot find the bindings for this. Where is your DTS? Was it tested?

It seems nothing here is documented.

Best regards,
Krzysztof