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Date:   Tue, 2 Jun 2020 10:21:18 +0200
From:   Krzysztof Kozlowski <krzk@kernel.org>
To:     Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc:     georgi.djakov@linaro.org, cw00.choi@samsung.com,
        a.swigon@samsung.com, myungjoo.ham@samsung.com,
        inki.dae@samsung.com, sw0312.kim@samsung.com,
        b.zolnierkie@samsung.com, m.szyprowski@samsung.com,
        linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v5 2/6] interconnect: Add generic interconnect driver
 for Exynos SoCs
Message-ID: <20200602082118.GB8216@kozik-lap>
References: <20200529163200.18031-1-s.nawrocki@samsung.com>
 <CGME20200529163223eucas1p2f663280abb499b4114b2f2930b43a4e5@eucas1p2.samsung.com>
 <20200529163200.18031-3-s.nawrocki@samsung.com>
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On Fri, May 29, 2020 at 06:31:56PM +0200, Sylwester Nawrocki wrote:
> This patch adds a generic interconnect driver for Exynos SoCs in order
> to provide interconnect functionality for each "samsung,exynos-bus"
> compatible device.
> 
> The SoC topology is a graph (or more specifically, a tree) and its
> edges are specified using the 'samsung,interconnect-parent' in the
> DT. Due to unspecified relative probing order, -EPROBE_DEFER may be
> propagated to ensure that the parent is probed before its children.
> 
> Each bus is now an interconnect provider and an interconnect node as
> well (cf. Documentation/interconnect/interconnect.rst), i.e. every bus
> registers itself as a node. Node IDs are not hardcoded but rather
> assigned dynamically at runtime. This approach allows for using this
> driver with various Exynos SoCs.
> 
> Frequencies requested via the interconnect API for a given node are
> propagated to devfreq using dev_pm_qos_update_request(). Please note
> that it is not an error when CONFIG_INTERCONNECT is 'n', in which
> case all interconnect API functions are no-op.
> 
> Signed-off-by: Artur Świgoń <a.swigon@samsung.com>
> Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
> 
> Changes for v5:
>  - adjust to renamed exynos,interconnect-parent-node property,
>  - use automatically generated platform device id as the interconect
>    node id instead of a now unavailable devfreq->id field,
>  - add icc_ prefix to some variables to make the code more self-commenting,
>  - use icc_nodes_remove() instead of icc_node_del() + icc_node_destroy(),
>  - adjust to exynos,interconnect-parent-node property rename to
>    samsung,interconnect-parent,
>  - converted to a separate platform driver in drivers/interconnect.
> ---
>  drivers/interconnect/Kconfig         |   1 +
>  drivers/interconnect/Makefile        |   1 +
>  drivers/interconnect/exynos/Kconfig  |   6 ++
>  drivers/interconnect/exynos/Makefile |   4 +
>  drivers/interconnect/exynos/exynos.c | 185 +++++++++++++++++++++++++++++++++++
>  5 files changed, 197 insertions(+)
>  create mode 100644 drivers/interconnect/exynos/Kconfig
>  create mode 100644 drivers/interconnect/exynos/Makefile
>  create mode 100644 drivers/interconnect/exynos/exynos.c
> 
> diff --git a/drivers/interconnect/Kconfig b/drivers/interconnect/Kconfig
> index 5b7204e..eca6eda 100644
> --- a/drivers/interconnect/Kconfig
> +++ b/drivers/interconnect/Kconfig
> @@ -11,6 +11,7 @@ menuconfig INTERCONNECT
>  
>  if INTERCONNECT
>  
> +source "drivers/interconnect/exynos/Kconfig"
>  source "drivers/interconnect/imx/Kconfig"
>  source "drivers/interconnect/qcom/Kconfig"
>  
> diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile
> index 4825c28..2ba1de6 100644
> --- a/drivers/interconnect/Makefile
> +++ b/drivers/interconnect/Makefile
> @@ -4,5 +4,6 @@ CFLAGS_core.o				:= -I$(src)
>  icc-core-objs				:= core.o
>  
>  obj-$(CONFIG_INTERCONNECT)		+= icc-core.o
> +obj-$(CONFIG_INTERCONNECT_EXYNOS)	+= exynos/
>  obj-$(CONFIG_INTERCONNECT_IMX)		+= imx/
>  obj-$(CONFIG_INTERCONNECT_QCOM)		+= qcom/
> diff --git a/drivers/interconnect/exynos/Kconfig b/drivers/interconnect/exynos/Kconfig
> new file mode 100644
> index 0000000..e51e52e
> --- /dev/null
> +++ b/drivers/interconnect/exynos/Kconfig
> @@ -0,0 +1,6 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config INTERCONNECT_EXYNOS
> +	tristate "Exynos generic interconnect driver"
> +	depends on ARCH_EXYNOS || COMPILE_TEST
> +	help
> +	  Generic interconnect driver for Exynos SoCs.
> diff --git a/drivers/interconnect/exynos/Makefile b/drivers/interconnect/exynos/Makefile
> new file mode 100644
> index 0000000..e19d1df
> --- /dev/null
> +++ b/drivers/interconnect/exynos/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0
> +exynos-interconnect-objs		:= exynos.o
> +
> +obj-$(CONFIG_INTERCONNECT_EXYNOS)	+= exynos-interconnect.o
> diff --git a/drivers/interconnect/exynos/exynos.c b/drivers/interconnect/exynos/exynos.c
> new file mode 100644
> index 0000000..8278194
> --- /dev/null
> +++ b/drivers/interconnect/exynos/exynos.c
> @@ -0,0 +1,185 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Exynos generic interconnect provider driver
> + *
> + * Copyright (c) 2020 Samsung Electronics Co., Ltd.
> + *
> + * Authors: Artur Świgoń <a.swigon@samsung.com>
> + *          Sylwester Nawrocki <s.nawrocki@samsung.com>
> + */
> +#include <linux/device.h>
> +#include <linux/interconnect-provider.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_qos.h>
> +
> +#define kbps_to_khz(x) ((x) / 8)
> +
> +struct exynos_icc_priv {
> +	struct device *dev;
> +
> +	/* One interconnect node per provider */
> +	struct icc_provider provider;
> +	struct icc_node *node;
> +
> +	struct dev_pm_qos_request qos_req;
> +};
> +
> +static struct icc_node *exynos_icc_get_parent(struct device_node *np)
> +{
> +	struct of_phandle_args args;
> +	int num, ret;
> +
> +	num = of_count_phandle_with_args(np, "samsung,interconnect-parent",
> +					"#interconnect-cells");
> +	if (num != 1)
> +		return NULL; /* parent nodes are optional */
> +
> +	ret = of_parse_phandle_with_args(np, "samsung,interconnect-parent",
> +					"#interconnect-cells", 0, &args);
> +	if (ret < 0)
> +		return ERR_PTR(ret);
> +
> +	of_node_put(args.np);
> +
> +	return of_icc_get_from_provider(&args);

I think of_node_put() should happen after of_icc_get_from_provider().

Best regards,
Krzysztof