Quoting Lee Jones (2015-02-18 08:15:00)
> Much h/w contain clocks which if turned off would prove fatal. The
> only way to recover is to restart the board(s). This driver takes
> references to clocks which are required to be always-on in order to
> prevent the common clk framework from trying to turn them off during
> the clk_disabled_unused() procedure.
>
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
> drivers/clk/Makefile | 1 +
> drivers/clk/clkdomain.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 64 insertions(+)
> create mode 100644 drivers/clk/clkdomain.c
>
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index d5fba5b..d9e2718 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -3,6 +3,7 @@ obj-$(CONFIG_HAVE_CLK) += clk-devres.o
> obj-$(CONFIG_CLKDEV_LOOKUP) += clkdev.o
> obj-$(CONFIG_COMMON_CLK) += clk.o
> obj-$(CONFIG_COMMON_CLK) += clk-divider.o
> +obj-$(CONFIG_COMMON_CLK) += clkdomain.o
> obj-$(CONFIG_COMMON_CLK) += clk-fixed-factor.o
> obj-$(CONFIG_COMMON_CLK) += clk-fixed-rate.o
> obj-$(CONFIG_COMMON_CLK) += clk-gate.o
> diff --git a/drivers/clk/clkdomain.c b/drivers/clk/clkdomain.c
> new file mode 100644
> index 0000000..8c83f99
> --- /dev/null
> +++ b/drivers/clk/clkdomain.c
Naming is hard. I'm not sure clkdomain.c is the best expression. Maybe
clk-alwon.c? I see ALWON used alot amongst hardware people who live in a
world of eight-character naming limitations.
> @@ -0,0 +1,63 @@
> +/*
> + * ST Clock Domain
> + *
> + * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
> + *
> + * Author: Lee Jones <lee.jones@xxxxxxxxxx>
> + *
> + * 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.
> + */
> +
> +#include <linux/clk-private.h>
If this header still existed I would berate you mercilessly. Luckily for
you it no longer exists and only causes a compile error ;-)
> +#include <linux/clk-provider.h>
> +#include <linux/of_address.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +static void ao_clock_domain_hog_clock(struct platform_device *pdev, int index)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + struct clk *clk;
> + int ret;
> +
> + clk = of_clk_get(np, index);
> + if (IS_ERR(clk)) {
> + dev_warn(&pdev->dev, "Failed get clock %s[%d]: %li\n",
> + np->full_name, index, PTR_ERR(clk));
> + return;
> + }
> +
> + ret = clk_prepare_enable(clk);
> + if (ret)
> + dev_warn(&pdev->dev, "Failed to enable clock: %s\n", clk->name);
> +}
> +
> +static int ao_clock_domain_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + int nclks, i;
> +
> + nclks = of_count_phandle_with_args(np, "clocks", "#clock-cells");
Minor nitpick: please use of_clk_get_parent_count. I spent a solid 5
minutes writing that function and I need people to use it so I can get a
return on my investment.
Otherwise the patch looks good. I believe that this method is targeting
always-on clock in a production environment, which is different from the
CLK_IGNORE_UNUSED stuff which typically is helpful while bringing up new
hardware or dealing with a platform that has incomplete driver support.
I wonder if there is a clever way for existing clock providers
(expressed in DT) to use this without having to create a separate node
of clocks with the "always-on-clk-domain" flag. Possibly the common
clock binding could declare some always-on flag that is standardized?
Then the framework core could use this code easily. Not sure if that is
a good idea though...
Regards,
Mike
> +
> + for (i = 0; i < nclks; i++)
> + ao_clock_domain_hog_clock(pdev, i);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id ao_clock_domain_match[] = {
> + { .compatible = "always-on-clk-domain" },
> + { },
> +};
> +
> +static struct platform_driver ao_clock_domain_driver = {
> + .probe = ao_clock_domain_probe,
> + .driver = {
> + .name = "always-on-clk-domain",
> + .of_match_table = ao_clock_domain_match,
> + },
> +};
> +module_platform_driver(ao_clock_domain_driver);
> --
> 1.9.1
>
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