Re: [PATCH v2 1/2] soc: rockchip: Register a soc_device to retrieve revision

["Heiko Stübner" <heiko@sntech.de>]

Hi Mylène,

Am Mittwoch, 1. April 2020, 17:35:12 CEST schrieb Mylène Josserand:
> Determine which revision of rk3288 by checking the HDMI version.
> According to the Rockchip BSP kernel/u-boot, on rk3288w, the HDMI
> revision equals 0x1A which is not the case for the rk3288.
> 
> As these SOC have some differences, this driver will help us
> to know on which revision we are by using 'soc_device' registration
> to be able to use 'soc_device_match' to detect rk3288/rk3288w.
> 
> Signed-off-by: Mylène Josserand <mylene.josserand@collabora.com>

I like your new approach quite a lot :-)

There are some things we need to take into account though, see below.


> ---
>  drivers/soc/rockchip/Makefile |   1 +
>  drivers/soc/rockchip/rk3288.c | 125 ++++++++++++++++++++++++++++++++++
>  2 files changed, 126 insertions(+)
>  create mode 100644 drivers/soc/rockchip/rk3288.c
> 
> diff --git a/drivers/soc/rockchip/Makefile b/drivers/soc/rockchip/Makefile
> index afca0a4c4b72..9dbf12913512 100644
> --- a/drivers/soc/rockchip/Makefile
> +++ b/drivers/soc/rockchip/Makefile
> @@ -2,5 +2,6 @@
>  #
>  # Rockchip Soc drivers
>  #
> +obj-$(CONFIG_ARCH_ROCKCHIP) += rk3288.o
>  obj-$(CONFIG_ROCKCHIP_GRF) += grf.o
>  obj-$(CONFIG_ROCKCHIP_PM_DOMAINS) += pm_domains.o
> diff --git a/drivers/soc/rockchip/rk3288.c b/drivers/soc/rockchip/rk3288.c

I'd really like this to be a soc.c instead of rk3288.c ;-)


> new file mode 100644
> index 000000000000..83379ba2b31b
> --- /dev/null
> +++ b/drivers/soc/rockchip/rk3288.c
> @@ -0,0 +1,125 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2020 Collabora Ltd
> + * Author: Mylene Josserand <mylene.josserand@collabora.com>
> + */
> +
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/sys_soc.h>
> +#include <linux/slab.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +
> +#define RK3288_HDMI_REV_REG	0x04
> +#define RK3288W_HDMI_REV	0x1A
> +
> +enum rk3288_soc_rev {
> +	RK3288_SOC_REV_NOT_DETECT,
> +	RK3288_SOC_REV_RK3288,
> +	RK3288_SOC_REV_RK3288W,
> +};
> +
> +static int rk3288_revision(void)
> +{
> +	static int revision = RK3288_SOC_REV_NOT_DETECT;
> +	struct device_node *dn;
> +	void __iomem *hdmi_base;
> +
> +	if (revision != RK3288_SOC_REV_NOT_DETECT)
> +		return revision;
> +
> +	dn = of_find_compatible_node(NULL, NULL, "rockchip,rk3288-dw-hdmi");
> +	if (!dn) {
> +		pr_err("%s: Couldn't find HDMI node\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	hdmi_base = of_iomap(dn, 0);
> +	of_node_put(dn);
> +
> +	if (!hdmi_base) {
> +		pr_err("%s: Couldn't map %pOF regs\n", __func__,
> +		       hdmi_base);
> +		return -ENXIO;
> +	}

The possible problem I see here is clocking and power-domain of the hdmi
controller in corner-cases. In the past we already had a lot of fun with
kexec, which also indicates that people actually use kexec productively.

So while all clocks are ungated and all power-domains are powered on first
boot, on a system without graphics the pclk+power-domain could be off when
doing a kexec into a second kernel, which then would probably hang here.


Of course with the hdmi-pclk being sourced from hclk_vio we run into a
chicken-egg-problem, as we need pclk_hdmi_ctrl to register hclk_vio at all.

So I guess one way out of this could be to
- amend rk3288_clk_shutdown() to also ungate the hdmi-pclk on shutdown
- add a shutdown mechanism to the power-domain driver so that it can
  enable PD_VIO on shutdown

> +
> +	if (readl_relaxed(hdmi_base + RK3288_HDMI_REV_REG)
> +	    == RK3288W_HDMI_REV)

nit: a nicer look would be something like
	val = readl_relaxed(hdmi_base + RK3288_HDMI_REV_REG);
	if (val == RK3288W_HDMI_REV)

> +		revision = RK3288_SOC_REV_RK3288W;
> +	else
> +		revision = RK3288_SOC_REV_RK3288;
> +
> +	iounmap(hdmi_base);
> +
> +	return revision;
> +}
> +
> +static const char *rk3288_socinfo_revision(u32 rev)
> +{
> +	const char *soc_rev;
> +
> +	switch (rev) {
> +	case RK3288_SOC_REV_RK3288:
> +		soc_rev = "RK3288";
> +		break;
> +
> +	case RK3288_SOC_REV_RK3288W:
> +		soc_rev = "RK3288w";

can we maybe use lower-case letters for all here?

> +		break;
> +
> +	case RK3288_SOC_REV_NOT_DETECT:
> +		soc_rev = "";
> +		break;
> +
> +	default:
> +		soc_rev = "unknown";
> +		break;
> +	}
> +
> +	return kstrdup_const(soc_rev, GFP_KERNEL);
> +}
> +
> +static const struct of_device_id rk3288_soc_match[] = {
> +	{ .compatible = "rockchip,rk3288", },
> +	{ }
> +};
> +
> +static int __init rk3288_soc_init(void)

as noted at the top, I'd really like to see this more generalized so that
other socs can just hook in there with a revision callback in a
rockchip_soc_data struct.


> +{
> +	struct soc_device_attribute *soc_dev_attr;
> +	struct soc_device *soc_dev;
> +	struct device_node *np;
> +
> +	np = of_find_matching_node(NULL, rk3288_soc_match);
> +	if (!np)
> +		return -ENODEV;
> +
> +	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
> +	if (!soc_dev_attr)
> +		return -ENOMEM;
> +
> +	soc_dev_attr->family = "Rockchip";
> +	soc_dev_attr->soc_id = "RK32xx";

nit: rk3288 instead of "32xx" please

> +
> +	np = of_find_node_by_path("/");
> +	of_property_read_string(np, "model", &soc_dev_attr->machine);
> +	of_node_put(np);
> +
> +	soc_dev_attr->revision = rk3288_socinfo_revision(rk3288_revision());
> +
> +	soc_dev = soc_device_register(soc_dev_attr);
> +	if (IS_ERR(soc_dev)) {
> +		kfree_const(soc_dev_attr->revision);
> +		kfree_const(soc_dev_attr->soc_id);
> +		kfree(soc_dev_attr);
> +		return PTR_ERR(soc_dev);
> +	}
> +
> +	dev_info(soc_device_to_device(soc_dev), "Rockchip %s %s detected\n",
> +		 soc_dev_attr->soc_id, soc_dev_attr->revision);

nit: dev_dbg should be enough, that information doesn't really matter for
most people, as it's only relevant to clock internals.


Heiko