Re: [PATCH v5 3/8] clk: tegra: Implement Tegra210 EMC clock

From: Dmitry Osipenko <digetx@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Jon Hunter <jonathanh@nvidia.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Joseph Lo <josephl@nvidia.com>,
	devicetree@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 3/8] clk: tegra: Implement Tegra210 EMC clock
Date: Tue, 10 Mar 2020 20:44:38 +0300	[thread overview]
Message-ID: <a5c9e3d6-2b65-ec93-d8f1-7c7680092e53@gmail.com> (raw)
In-Reply-To: <20200310152003.2945170-4-thierry.reding@gmail.com>

10.03.2020 18:19, Thierry Reding пишет:
> From: Joseph Lo <josephl@nvidia.com>
> 
> The EMC clock needs to carefully coordinate with the EMC controller
> programming to make sure external memory can be properly clocked. Do so
> by hooking up the EMC clock with an EMC provider that will specify which
> rates are supported by the EMC and provide a callback to use for setting
> the clock rate at the EMC.
> 
> Based on work by Peter De Schrijver <pdeschrijver@nvidia.com>.
> 
> Signed-off-by: Joseph Lo <josephl@nvidia.com>
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
> Changes in v5:
> - major rework and cleanup

...
> +static u8 tegra210_clk_emc_get_parent(struct clk_hw *hw)
> +{
> +	struct tegra210_clk_emc *emc = to_tegra210_clk_emc(hw);
> +	u32 value;
> +	u8 src;
> +
> +	value = readl_relaxed(emc->regs + CLK_SOURCE_EMC);
> +	src = (value >> CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT) &
> +			CLK_SOURCE_EMC_2X_CLK_SRC_MASK;

What about to use a generic FIELD_GET/PREP()?

> +static int tegra210_clk_emc_set_rate(struct clk_hw *hw, unsigned long rate,
> +				     unsigned long parent_rate)
> +{
> +	struct tegra210_clk_emc *emc = to_tegra210_clk_emc(hw);
> +	struct tegra210_clk_emc_provider *provider = emc->provider;
> +	struct tegra210_clk_emc_config *config;
> +	struct device *dev = provider->dev;
> +	struct clk_hw *old, *new, *parent;
> +	u8 old_idx, new_idx, index;
> +	struct clk *clk;
> +	unsigned int i;
> +	int err;
> +
> +	if (!provider || !provider->configs || provider->num_configs == 0)
> +		return -EINVAL;

Why all these checks are needed? I don't think it ever could fail,
couldn't it?

> +static int emc_table_lookup(struct tegra_emc *emc, unsigned long rate)
> +{
> +	int i;

unsigned int

Same for all other occurrences in the code.