Re: [PATCH v8 11/26] memory: tegra124-emc: Make driver modular

[Krzysztof Kozlowski <krzk@kernel.org>]

On Wed, Nov 11, 2020 at 04:14:41AM +0300, Dmitry Osipenko wrote:
> Add modularization support to the Tegra124 EMC driver, which now can be
> compiled as a loadable kernel module.
> 
> Note that EMC clock must be registered at clk-init time, otherwise PLLM
> will be disabled as unused clock at boot time if EMC driver is compiled
> as a module. Hence add a prepare/complete callbacks. similarly to what is
> done for the Tegra20/30 EMC drivers.
> 
> Tested-by: Nicolas Chauvet <kwizart@gmail.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/clk/tegra/Makefile           |  3 +-
>  drivers/clk/tegra/clk-tegra124-emc.c | 41 ++++++++++++++++++++++++----
>  drivers/clk/tegra/clk-tegra124.c     | 27 ++++++++++++++++--
>  drivers/clk/tegra/clk.h              | 16 +++--------
>  drivers/memory/tegra/Kconfig         |  2 +-
>  drivers/memory/tegra/tegra124-emc.c  | 31 ++++++++++++++-------
>  include/linux/clk/tegra.h            |  8 ++++++
>  include/soc/tegra/emc.h              | 16 -----------
>  8 files changed, 96 insertions(+), 48 deletions(-)
>  delete mode 100644 include/soc/tegra/emc.h
> 
> diff --git a/drivers/clk/tegra/Makefile b/drivers/clk/tegra/Makefile
> index eec2313fd37e..53b76133e905 100644
> --- a/drivers/clk/tegra/Makefile
> +++ b/drivers/clk/tegra/Makefile
> @@ -22,7 +22,8 @@ obj-$(CONFIG_ARCH_TEGRA_3x_SOC)		+= clk-tegra20-emc.o
>  obj-$(CONFIG_ARCH_TEGRA_114_SOC)	+= clk-tegra114.o
>  obj-$(CONFIG_ARCH_TEGRA_124_SOC)	+= clk-tegra124.o
>  obj-$(CONFIG_TEGRA_CLK_DFLL)		+= clk-tegra124-dfll-fcpu.o
> -obj-$(CONFIG_TEGRA124_EMC)		+= clk-tegra124-emc.o
> +obj-$(CONFIG_ARCH_TEGRA_124_SOC)	+= clk-tegra124-emc.o
> +obj-$(CONFIG_ARCH_TEGRA_132_SOC)	+= clk-tegra124-emc.o

How is it related to modularization? It looks like different issue is
fixed here.

>  obj-$(CONFIG_ARCH_TEGRA_132_SOC)	+= clk-tegra124.o
>  obj-y					+= cvb.o
>  obj-$(CONFIG_ARCH_TEGRA_210_SOC)	+= clk-tegra210.o
> diff --git a/drivers/clk/tegra/clk-tegra124-emc.c b/drivers/clk/tegra/clk-tegra124-emc.c
> index 745f9faa98d8..bdf6f4a51617 100644
> --- a/drivers/clk/tegra/clk-tegra124-emc.c
> +++ b/drivers/clk/tegra/clk-tegra124-emc.c
> @@ -11,7 +11,9 @@
>  #include <linux/clk-provider.h>
>  #include <linux/clk.h>
>  #include <linux/clkdev.h>
> +#include <linux/clk/tegra.h>
>  #include <linux/delay.h>
> +#include <linux/export.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/of_address.h>
> @@ -21,7 +23,6 @@
>  #include <linux/string.h>
>  
>  #include <soc/tegra/fuse.h>
> -#include <soc/tegra/emc.h>
>  
>  #include "clk.h"
>  
> @@ -80,6 +81,9 @@ struct tegra_clk_emc {
>  	int num_timings;
>  	struct emc_timing *timings;
>  	spinlock_t *lock;
> +
> +	tegra124_emc_prepare_timing_change_cb *prepare_timing_change;
> +	tegra124_emc_complete_timing_change_cb *complete_timing_change;
>  };
>  
>  /* Common clock framework callback implementations */
> @@ -176,6 +180,9 @@ static struct tegra_emc *emc_ensure_emc_driver(struct tegra_clk_emc *tegra)
>  	if (tegra->emc)
>  		return tegra->emc;
>  
> +	if (!tegra->prepare_timing_change || !tegra->complete_timing_change)
> +		return NULL;
> +
>  	if (!tegra->emc_node)
>  		return NULL;
>  
> @@ -241,7 +248,7 @@ static int emc_set_timing(struct tegra_clk_emc *tegra,
>  
>  	div = timing->parent_rate / (timing->rate / 2) - 2;
>  
> -	err = tegra_emc_prepare_timing_change(emc, timing->rate);
> +	err = tegra->prepare_timing_change(emc, timing->rate);
>  	if (err)
>  		return err;
>  
> @@ -259,7 +266,7 @@ static int emc_set_timing(struct tegra_clk_emc *tegra,
>  
>  	spin_unlock_irqrestore(tegra->lock, flags);
>  
> -	tegra_emc_complete_timing_change(emc, timing->rate);
> +	tegra->complete_timing_change(emc, timing->rate);
>  
>  	clk_hw_reparent(&tegra->hw, __clk_get_hw(timing->parent));
>  	clk_disable_unprepare(tegra->prev_parent);
> @@ -473,8 +480,8 @@ static const struct clk_ops tegra_clk_emc_ops = {
>  	.get_parent = emc_get_parent,
>  };
>  
> -struct clk *tegra_clk_register_emc(void __iomem *base, struct device_node *np,
> -				   spinlock_t *lock)
> +struct clk *tegra124_clk_register_emc(void __iomem *base, struct device_node *np,
> +				      spinlock_t *lock)
>  {
>  	struct tegra_clk_emc *tegra;
>  	struct clk_init_data init;
> @@ -538,3 +545,27 @@ struct clk *tegra_clk_register_emc(void __iomem *base, struct device_node *np,
>  
>  	return clk;
>  };
> +
> +void tegra124_clk_set_emc_callbacks(tegra124_emc_prepare_timing_change_cb *prep_cb,
> +				    tegra124_emc_complete_timing_change_cb *complete_cb)
> +{
> +	struct clk *clk = __clk_lookup("emc");
> +	struct tegra_clk_emc *tegra;
> +	struct clk_hw *hw;
> +
> +	if (clk) {
> +		hw = __clk_get_hw(clk);
> +		tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +		tegra->prepare_timing_change = prep_cb;
> +		tegra->complete_timing_change = complete_cb;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(tegra124_clk_set_emc_callbacks);
> +
> +bool tegra124_clk_emc_driver_available(struct clk_hw *hw)
> +{
> +	struct tegra_clk_emc *tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +	return tegra->prepare_timing_change && tegra->complete_timing_change;
> +}
> diff --git a/drivers/clk/tegra/clk-tegra124.c b/drivers/clk/tegra/clk-tegra124.c
> index e931319dcc9d..b4f2ae4066a6 100644
> --- a/drivers/clk/tegra/clk-tegra124.c
> +++ b/drivers/clk/tegra/clk-tegra124.c
> @@ -929,6 +929,7 @@ static struct tegra_clk tegra124_clks[tegra_clk_max] __initdata = {
>  	[tegra_clk_audio4_mux] = { .dt_id = TEGRA124_CLK_AUDIO4_MUX, .present = true },
>  	[tegra_clk_spdif_mux] = { .dt_id = TEGRA124_CLK_SPDIF_MUX, .present = true },
>  	[tegra_clk_cec] = { .dt_id = TEGRA124_CLK_CEC, .present = true },
> +	[tegra_clk_emc] = { .dt_id = TEGRA124_CLK_EMC, .present = false },
>  };
>  
>  static struct tegra_devclk devclks[] __initdata = {
> @@ -1500,6 +1501,26 @@ static void __init tegra124_132_clock_init_pre(struct device_node *np)
>  	writel(plld_base, clk_base + PLLD_BASE);
>  }
>  
> +static struct clk *tegra124_clk_src_onecell_get(struct of_phandle_args *clkspec,
> +						void *data)
> +{
> +	struct clk_hw *hw;
> +	struct clk *clk;
> +
> +	clk = of_clk_src_onecell_get(clkspec, data);
> +	if (IS_ERR(clk))
> +		return clk;
> +
> +	hw = __clk_get_hw(clk);
> +
> +	if (clkspec->args[0] == TEGRA124_CLK_EMC) {
> +		if (!tegra124_clk_emc_driver_available(hw))
> +			return ERR_PTR(-EPROBE_DEFER);
> +	}
> +
> +	return clk;
> +}
> +
>  /**
>   * tegra124_132_clock_init_post - clock initialization postamble for T124/T132
>   * @np: struct device_node * of the DT node for the SoC CAR IP block
> @@ -1516,10 +1537,10 @@ static void __init tegra124_132_clock_init_post(struct device_node *np)
>  				  &pll_x_params);
>  	tegra_init_special_resets(1, tegra124_reset_assert,
>  				  tegra124_reset_deassert);
> -	tegra_add_of_provider(np, of_clk_src_onecell_get);
> +	tegra_add_of_provider(np, tegra124_clk_src_onecell_get);
>  
> -	clks[TEGRA124_CLK_EMC] = tegra_clk_register_emc(clk_base, np,
> -							&emc_lock);
> +	clks[TEGRA124_CLK_EMC] = tegra124_clk_register_emc(clk_base, np,
> +							   &emc_lock);
>  
>  	tegra_register_devclks(devclks, ARRAY_SIZE(devclks));
>  
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index 6b565f6b5f66..2da7c93c1a6c 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -881,18 +881,6 @@ void tegra_super_clk_gen5_init(void __iomem *clk_base,
>  			void __iomem *pmc_base, struct tegra_clk *tegra_clks,
>  			struct tegra_clk_pll_params *pll_params);
>  
> -#ifdef CONFIG_TEGRA124_EMC
> -struct clk *tegra_clk_register_emc(void __iomem *base, struct device_node *np,
> -				   spinlock_t *lock);
> -#else
> -static inline struct clk *tegra_clk_register_emc(void __iomem *base,
> -						 struct device_node *np,
> -						 spinlock_t *lock)
> -{
> -	return NULL;
> -}
> -#endif

Why clock changes are so tightly coupled with making an EMC driver
modular? Usually this should be a separate change - you adjust any
dependencies to accept late or deferred probing, exported symbols,
loosen the coupling between drivers, etc. and then you convert something
to module.

Best regards,
Krzysztof