linux-kernel - Re: [PATCH v2] memory: tegra: Add support for DBB clock on Tegra264

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Message-ID: <7510a358-608a-475f-9f71-50fa72a72d27@nvidia.com>
Date: Fri, 16 Jan 2026 13:15:11 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Thierry Reding <thierry.reding@...il.com>,
 Krzysztof Kozlowski <krzk@...nel.org>
Cc: linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] memory: tegra: Add support for DBB clock on Tegra264


On 16/01/2026 12:37, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> The DBB clock is needed by many IP blocks in order to access system
> memory via the data backbone. The memory controller and external memory
> controllers are the central place where these accesses are managed, so
> make sure that the clock can be controlled from the corresponding
> driver.
> 
> Note that not all drivers fully register bandwidth requests, and hence
> the EMC driver doesn't have enough information to know when it's safe to
> switch the clock off, so for now it will be kept on permanently.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
> Changes in v2:
> - convert to dev_err_probe() (Krzysztof)
> 
>   drivers/memory/tegra/tegra186-emc.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/memory/tegra/tegra186-emc.c b/drivers/memory/tegra/tegra186-emc.c
> index dfddceecdd1a..03ebab6fbe68 100644
> --- a/drivers/memory/tegra/tegra186-emc.c
> +++ b/drivers/memory/tegra/tegra186-emc.c
> @@ -22,6 +22,7 @@ struct tegra186_emc {
>   	struct tegra_bpmp *bpmp;
>   	struct device *dev;
>   	struct clk *clk;
> +	struct clk *clk_dbb;
>   
>   	struct tegra186_emc_dvfs *dvfs;
>   	unsigned int num_dvfs;
> @@ -328,6 +329,13 @@ static int tegra186_emc_probe(struct platform_device *pdev)
>   		goto put_bpmp;
>   	}
>   
> +	emc->clk_dbb = devm_clk_get_optional_enabled(&pdev->dev, "dbb");
> +	if (IS_ERR(emc->clk_dbb)) {
> +		err = dev_err_probe(&pdev->dev, PTR_ERR(emc->clk_dbb),
> +				    "failed to get DBB clock\n");
> +		goto put_bpmp;
> +	}
> +
>   	platform_set_drvdata(pdev, emc);
>   	emc->dev = &pdev->dev;
>   

Looks good to me!

Reviewed-by: Jon Hunter <jonathanh@...dia.com>

Cheers
Jon

-- 
nvpublic