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Date: Mon, 14 Sep 2015 09:14:19 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc: Simon <horms@...ge.net.au>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...eaurora.org>,
linux-clk <linux-clk@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Magnus <magnus.damm@...il.com>,
Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH] clk: add CS2000 Fractional-N driver
Hi Morimoto-san,
On Mon, Sep 14, 2015 at 4:55 AM, Kuninori Morimoto
<kuninori.morimoto.gx@...esas.com> wrote:
> From: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
>
> This patch adds CS2000 Fractional-N driver as clock provider.
> It is useful if it supports runtime clock setting, but it supports
> fixed clock rate only at this point.
>
> Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Thanks for your patch!
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/cs2000-cp.txt
> @@ -0,0 +1,20 @@
> +CIRRUS LOGIC Fractional-N Clock Synthesizer & Clock Multiplier
> +
> +Required properties:
> +
> +- compatible: "cirrus,cs2000-cp"
> +- reg: The chip select number on the I2C bus
> +- clocks: common clock binding for CLK_IN, XTI/REF_CLK
As you have multiple inputs, I think it makes sense to use "clock-names".
> --- /dev/null
> +++ b/drivers/clk/clk-cs2000-cp.c
> @@ -0,0 +1,379 @@
> +/*
> + * CS2000 -- CIRRUS LOGIC Fractional-N Clock Synthesizer & Clock Multiplier
> + *
> + * Copyright (C) 2015 Renesas Electronics Corporation
> + * Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#include <linux/clk-provider.h>
> +#include <linux/delay.h>
> +#include <linux/clk.h>
> +#include <linux/i2c.h>
> +#include <linux/of_device.h>
> +#include <linux/module.h>
> +
> +#define CLK_MAIN 0 /* CLK_IN on datasheet */
> +#define CLK_IN 1 /* REF_CLK on datasheet */
Why do you call them differently from the datasheet?
Especially the different CLK_IN can be confusing.
> +#define cs2000_read(c, addr) i2c_smbus_read_byte_data(c, addr)
> +static void cs2000_write(struct i2c_client *client, u8 addr, u8 val)
> +{
> + struct device *dev = &client->dev;
> +
> + dev_dbg(dev, "0x%02x : 0x%02x\n", addr, val);
> +
> + i2c_smbus_write_byte_data(client, addr, val);
This can fail, so the error should be propagated, and checked in all
callers of cs2000_write().
> +}
> +
> +static void cs2000_bset(struct i2c_client *client, u8 addr, u8 mask, u8 val)
> +{
> + u32 data;
i2c_smbus_read_byte_data returns s32, and the return value will be
negative in case of a failure.
> + data = cs2000_read(client, addr);
Should check for failure.
> + data &= ~mask;
> + data |= (val & mask);
> +
> + cs2000_write(client, addr, data);
> +}
> +static int cs2000_ratio_set(struct i2c_client *client,
> + int ch, u32 rate_in, u64 rate_out)
> +{
> + u32 val;
> + int i;
unsigned int i
> + if (CH_ERR(ch))
I think it's more readable to drop the CH_ERR() macro, and open code
"(ch < 0) || (ch >= CH_MAX)" (also in cs2000_ratio_select()).
> + return -EINVAL;
> +
> + /*
> + * ratio = rate_out / rate_in * 2^20
> + *
> + * To avoid over flow, rate_out is u64
> + * The result should be u32
> + */
> +
> + val = rate_out * (1 << 20) / rate_in;
Please use do_div() for 64-by-32 divides, as full 64-bit divisions are
usually not available on 32-bit architectures.
> +static int cs2000_clk_get(struct i2c_client *client,
> + u32 *rate_in, u32 *rate_out)
> +{
> + struct cs2000_priv *priv = i2c_get_clientdata(client);
> + struct device *dev = &client->dev;
> + struct device_node *np = dev->of_node;
> + struct clk *clk_main, *clk_in;
> +
> + clk_main = of_clk_get(np, CLK_MAIN);
> + /* not yet provided */
> + if (IS_ERR(clk_main))
> + return -EPROBE_DEFER;
> +
> + clk_in = of_clk_get(np, CLK_IN);
> + if (IS_ERR(clk_in))
> + return PTR_ERR(clk_in);
Named clk_get(), for both?
> +static int cs2000_wait_pll_lock(struct i2c_client *client)
> +{
> + struct device *dev = &client->dev;
> + u32 val;
> + int i;
unsigned int
> +static int cs2000_version_print(struct i2c_client *client)
> +{
> + struct device *dev = &client->dev;
> + u32 val = cs2000_read(client, DEVICE_ID);
"s32 val", and please check for failures.
> + char *revision;
const char *revision;
> + /* CS2000 should be 0x0 */
> + if (0 != (val >> 3))
> + return -EIO;
> +
> + switch (val & 0x7) {
> + case 0x4:
> + revision = "B2 / B3";
> + break;
> + case 0x6:
> + revision = "C1";
> + break;
> + default:
> + return -EIO;
> + }
> +
> + dev_info(dev, "revision - %s\n", revision);
> +
> + return 0;
> +}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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