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Date:   Fri, 3 Nov 2017 17:37:34 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     Kaihua Zhong <zhongkaihua@...wei.com>, mturquette@...libre.com,
        sboyd@...eaurora.org, robh+dt@...nel.org, mark.rutland@....com,
        xuwei5@...ilicon.com, catalin.marinas@....com, will.deacon@....com,
        xuejiancheng@...ilicon.com, wenpan@...ilicon.com,
        leo.yan@...aro.org, zhangfei.gao@...aro.org, guodong.xu@...aro.org,
        chenjun14@...wei.com
Cc:     linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        suzhuangluan@...ilicon.com, xuezhiliang@...ilicon.com,
        kevin.wangtao@...ilicon.com
Subject: Re: [PATCH 2/3] clk: hisilicon: Add support for Hi3660 stub clocks

Hi Kaihua,

On 03/11/17 07:25, Kaihua Zhong wrote:
> Hi3660 has four stub clocks, which are big and LITTLE cluster clocks,
> GPU clock and DDR clock.  These clocks ask MCU for frequency scaling
> by sending message through mailbox.
> 
> This commit adds support for stub clocks, it requests the dedicated
> mailbox channel at initialization; then later uses this channel to send
> message to MCU to execute frequency scaling. The four stub clocks share
> the same mailbox channel, but every stub clock has its own command id so
> MCU can distinguish the requirement coming for which clock.
> 
> A shared memory is used to present effective frequency value, so the
> clock driver uses I/O mapping for the memory and reads back rate value.
> 
> Reviewed-by: Leo Yan <leo.yan@...aro.org>
> Signed-off-by: Kai Zhao <zhaokai1@...ilicon.com>
> Signed-off-by: Kevin Wang <kevin.wangtao@...ilicon.com>
> Signed-off-by: Ruyi Wang <wangruyi@...wei.com>
> Signed-off-by: Kaihua Zhong <zhongkaihua@...wei.com>
> ---
>   drivers/clk/hisilicon/Kconfig            |   6 +
>   drivers/clk/hisilicon/Makefile           |   1 +
>   drivers/clk/hisilicon/clk-hi3660-stub.c  | 195 +++++++++++++++++++++++++++++++
>   include/dt-bindings/clock/hi3660-clock.h |   7 ++
>   4 files changed, 209 insertions(+)
>   create mode 100644 drivers/clk/hisilicon/clk-hi3660-stub.c
> 
> diff --git a/drivers/clk/hisilicon/Kconfig b/drivers/clk/hisilicon/Kconfig
> index 7098bfd..1bd4355 100644
> --- a/drivers/clk/hisilicon/Kconfig
> +++ b/drivers/clk/hisilicon/Kconfig
> @@ -49,3 +49,9 @@ config STUB_CLK_HI6220
>   	default ARCH_HISI
>   	help
>   	  Build the Hisilicon Hi6220 stub clock driver.
> +
> +config STUB_CLK_HI3660
> +	bool "Hi3660 Stub Clock Driver"
> +	depends on COMMON_CLK_HI3660 && MAILBOX
> +	help
> +	  Build the Hisilicon Hi3660 stub clock driver.
> diff --git a/drivers/clk/hisilicon/Makefile b/drivers/clk/hisilicon/Makefile
> index 1e4c3dd..0a5b499 100644
> --- a/drivers/clk/hisilicon/Makefile
> +++ b/drivers/clk/hisilicon/Makefile
> @@ -14,3 +14,4 @@ obj-$(CONFIG_COMMON_CLK_HI3798CV200)	+= crg-hi3798cv200.o
>   obj-$(CONFIG_COMMON_CLK_HI6220)	+= clk-hi6220.o
>   obj-$(CONFIG_RESET_HISI)	+= reset.o
>   obj-$(CONFIG_STUB_CLK_HI6220)	+= clk-hi6220-stub.o
> +obj-$(CONFIG_STUB_CLK_HI3660)	+= clk-hi3660-stub.o
> diff --git a/drivers/clk/hisilicon/clk-hi3660-stub.c b/drivers/clk/hisilicon/clk-hi3660-stub.c
> new file mode 100644
> index 0000000..0a21c91
> --- /dev/null
> +++ b/drivers/clk/hisilicon/clk-hi3660-stub.c
> @@ -0,0 +1,195 @@
> +/*
> + * Hisilicon clock driver
> + *
> + * Copyright (c) 2013-2017 Hisilicon Limited.
> + * Copyright (c) 2017 Linaro Limited.
> + *
> + * Author: Kai Zhao <zhaokai1@...ilicon.com>
> + * Author: Tao Wang <kevin.wangtao@...ilicon.com>
> + * Author: Leo Yan <leo.yan@...aro.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/mailbox_client.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <dt-bindings/clock/hi3660-clock.h>
> +
> +#define HI3660_STUB_CLOCK_DATA		(0x70)
> +#define MHZ				(1000 * 1000)
> +
> +#define DEFINE_CLK_STUB(_id, _cmd, _name)			\
> +	{							\
> +		.id = (_id),					\
> +		.cmd = (_cmd),					\
> +		.hw.init = &(struct clk_init_data) {		\
> +			.name = #_name,				\
> +			.ops = &hi3660_stub_clk_ops,		\
> +			.num_parents = 0,			\
> +			.flags = CLK_GET_RATE_NOCACHE,		\
> +		},						\
> +	},
> +
> +#define to_stub_clk(_hw) container_of(_hw, struct hi3660_stub_clk, hw)
> +
> +struct hi3660_stub_clk_chan {
> +	struct mbox_client cl;
> +	struct mbox_chan *mbox;
> +};
> +
> +struct hi3660_stub_clk {
> +	unsigned int id;
> +	struct device *dev;

I don't understand why you need to keep this. The only place it is used 
it for the debug message in hi3660_stub_clk_set_rate and you could get 
the device pointer by doing chan->cl.dev since all the stub_clk point to 
the same device.

> +	struct clk_hw hw;
> +	unsigned int cmd;
> +	unsigned int msg[8];
> +	unsigned int rate;
> +};
> +
> +static void __iomem *freq_reg;
> +static struct hi3660_stub_clk_chan *chan;

I would suggest having a slightly longer name than "chan" as this can 
easily get shadowed which is bad for a non-local variable.

Also, maybe you could not declare it as a pointer and avoid the need for 
kzalloc in the probe function.

> +
> +static unsigned long hi3660_stub_clk_recalc_rate(struct clk_hw *hw,
> +						 unsigned long parent_rate)
> +{
> +	struct hi3660_stub_clk *stub_clk = to_stub_clk(hw);
> +
> +	/*
> +	 * LPM3 writes back the CPU frequency in shared SRAM so read
> +	 * back the frequency.
> +	 */
> +	stub_clk->rate = readl(freq_reg + (stub_clk->id << 2)) * MHZ;
> +	return stub_clk->rate;
> +}
> +
> +static long hi3660_stub_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> +				       unsigned long *prate)
> +{
> +	/*
> +	 * LPM3 handles rate rounding so just return whatever
> +	 * rate is requested.
> +	 */
> +	return rate;
> +}
> +
> +static int hi3660_stub_clk_set_rate(struct clk_hw *hw, unsigned long rate,
> +				    unsigned long parent_rate)
> +{
> +	struct hi3660_stub_clk *stub_clk = to_stub_clk(hw);
> +
> +	stub_clk->msg[0] = stub_clk->cmd;
> +	stub_clk->msg[1] = rate / MHZ;
> +
> +	dev_dbg(stub_clk->dev, "set rate msg[0]=0x%x msg[1]=0x%x\n",
> +		stub_clk->msg[0], stub_clk->msg[1]);
> +
> +	mbox_send_message(chan->mbox, stub_clk->msg);
> +	mbox_client_txdone(chan->mbox, 0);
> +
> +	stub_clk->rate = rate;
> +	return 0;
> +}
> +
> +static const struct clk_ops hi3660_stub_clk_ops = {
> +	.recalc_rate    = hi3660_stub_clk_recalc_rate,
> +	.round_rate     = hi3660_stub_clk_round_rate,
> +	.set_rate       = hi3660_stub_clk_set_rate,
> +};
> +
> +static struct hi3660_stub_clk hi3660_stub_clks[HI3660_CLK_STUB_NUM] = {
> +	DEFINE_CLK_STUB(HI3660_CLK_STUB_CLUSTER0, 0x0001030A, "cpu-cluster.0")
> +	DEFINE_CLK_STUB(HI3660_CLK_STUB_CLUSTER1, 0x0002030A, "cpu-cluster.1")
> +	DEFINE_CLK_STUB(HI3660_CLK_STUB_GPU, 0x0003030A, "clk-g3d")
> +	DEFINE_CLK_STUB(HI3660_CLK_STUB_DDR, 0x00040309, "clk-ddrc")
> +};
> +
> +static struct clk_hw *hi3660_stub_clk_hw_get(struct of_phandle_args *clkspec,
> +					     void *data)
> +{
> +	unsigned int idx = clkspec->args[0];
> +
> +	if (idx > HI3660_CLK_STUB_NUM) {
> +		pr_err("%s: invalid index %u\n", __func__, idx);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return &hi3660_stub_clks[idx].hw;
> +}
> +
> +static int hi3660_stub_clk_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct resource *res;
> +	unsigned int i;
> +	int ret;
> +
> +	chan = devm_kzalloc(dev, sizeof(*chan), GFP_KERNEL);
> +	if (!chan)
> +		return -ENOMEM;
> +
> +	/* Use mailbox client without blocking */
> +	chan->cl.dev = dev;
> +	chan->cl.tx_done = NULL;
> +	chan->cl.tx_block = false;
> +	chan->cl.knows_txdone = false;
> +
> +	/* Allocate mailbox channel */
> +	chan->mbox = mbox_request_channel(&chan->cl, 0);
> +	if (IS_ERR(chan->mbox))
> +		return PTR_ERR(chan->mbox);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	freq_reg = devm_ioremap(dev, res->start, resource_size(res));
> +	if (IS_ERR(freq_reg))
> +		return -ENOMEM;
> +
> +	freq_reg += HI3660_STUB_CLOCK_DATA;
> +
> +	for (i = 0; i < HI3660_CLK_STUB_NUM; i++) {
> +		hi3660_stub_clks[i].dev = dev;
> +		ret = devm_clk_hw_register(&pdev->dev, &hi3660_stub_clks[i].hw);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = of_clk_add_hw_provider(pdev->dev.of_node, hi3660_stub_clk_hw_get,
> +				     hi3660_stub_clks);
> +	if (ret)
> +		return ret;
> +
> +	return 0;

Hmmm, you could just return ret here without needing the branch.

Cheers,

-- 
Julien Thierry

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