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SubjectRe: [PATCH 2/2] reset: Add Broadcom STB RESCAL reset controller
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Hi Florian, Jim,

On Tue, 2019-12-10 at 11:59 -0800, Florian Fainelli wrote:
> From: Jim Quinlan <jim2101024@gmail.com>
>
> On BCM7216 there is a special purpose reset controller named RESCAL
> (reset calibration) which is necessary for SATA and PCIe0/1 to operate
> correctly. This commit adds support for such a reset controller to be
> available.
>
> Signed-off-by: Jim Quinlan <im2101024@gmail.com>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> drivers/reset/Kconfig | 7 ++
> drivers/reset/Makefile | 1 +
> drivers/reset/reset-brcmstb-rescal.c | 124 +++++++++++++++++++++++++++
> 3 files changed, 132 insertions(+)
> create mode 100644 drivers/reset/reset-brcmstb-rescal.c
>
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index 12f5c897788d..b7cc0a2049d9 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -49,6 +49,13 @@ config RESET_BRCMSTB
> This enables the reset controller driver for Broadcom STB SoCs using
> a SUN_TOP_CTRL_SW_INIT style controller.
>
> +config RESET_BRCMSTB_RESCAL
> + bool "Broadcom STB RESCAL reset controller"
> + default ARCH_BRCMSTB || COMPILE_TEST
> + help
> + This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on
> + BCM7216.
> +
> config RESET_HSDK
> bool "Synopsys HSDK Reset Driver"
> depends on HAS_IOMEM
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 00767c03f5f2..1e4291185c52 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_RESET_ATH79) += reset-ath79.o
> obj-$(CONFIG_RESET_AXS10X) += reset-axs10x.o
> obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
> obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
> +obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
> obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
> obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
> obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
> diff --git a/drivers/reset/reset-brcmstb-rescal.c b/drivers/reset/reset-brcmstb-rescal.c
> new file mode 100644
> index 000000000000..58a30e624a14
> --- /dev/null
> +++ b/drivers/reset/reset-brcmstb-rescal.c
> @@ -0,0 +1,124 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2018 Broadcom */
> +
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +#include <linux/types.h>
> +
> +#define BRCM_RESCAL_START 0
> +#define BRCM_RESCAL_START_BIT BIT(0)
> +#define BRCM_RESCAL_CTRL 4
> +#define BRCM_RESCAL_STATUS 8
> +#define BRCM_RESCAL_STATUS_BIT BIT(0)

Is there any reason the start bit is indented but the status bit is not?

> +
> +struct brcm_rescal_reset {
> + void __iomem *base;
> + struct device *dev;
> + struct reset_controller_dev rcdev;
> +};
> +
> +static int brcm_rescal_reset_assert(struct reset_controller_dev *rcdev,
> + unsigned long id)
> +{
> + return 0;
> +}

Please do not implement the assert operation if it doesn't cause a reset
line to be asserted afterwards.
The reset core will return 0 from reset_control_assert() for shared
reset controls if .assert is not implemented.

> +
> +static int brcm_rescal_reset_deassert(struct reset_controller_dev *rcdev,
> + unsigned long id)
> +{
> + struct brcm_rescal_reset *data =
> + container_of(rcdev, struct brcm_rescal_reset, rcdev);
> + void __iomem *base = data->base;
> + const int NUM_RETRIES = 10;
> + u32 reg;
> + int i;
> +
> + reg = readl(base + BRCM_RESCAL_START);
> + writel(reg | BRCM_RESCAL_START_BIT, base + BRCM_RESCAL_START);
> + reg = readl(base + BRCM_RESCAL_START);

Are there any other fields beside the START_BIT in this register?

> + if (!(reg & BRCM_RESCAL_START_BIT)) {
> + dev_err(data->dev, "failed to start sata/pcie rescal\n");
> + return -EIO;
> + }
> +
> + reg = readl(base + BRCM_RESCAL_STATUS);
> + for (i = NUM_RETRIES; i >= 0 && !(reg & BRCM_RESCAL_STATUS_BIT); i--) {
> + udelay(100);
> + reg = readl(base + BRCM_RESCAL_STATUS);
> + }

This timeout loop should be replaced by a single readl_poll_timeout().
At 100 µs waits per iteration this could use the sleeping variant.

> + if (!(reg & BRCM_RESCAL_STATUS_BIT)) {
> + dev_err(data->dev, "timedout on sata/pcie rescal\n");
> + return -ETIMEDOUT;
> + }
> +
> + reg = readl(base + BRCM_RESCAL_START);
> + writel(reg ^ BRCM_RESCAL_START_BIT, base + BRCM_RESCAL_START);

Please use &= ~BRCM_RESCAL_START_BIT instead.

> + reg = readl(base + BRCM_RESCAL_START);
> + dev_dbg(data->dev, "sata/pcie rescal success\n");
> +
> + return 0;
> +}

This whole function looks a lot like it doesn't just deassert a reset
line, but actually issues a complete reset procedure of some kind. Do
you have some insight on what actually happens in the hardware when the
start bit is triggered? I suspect this should be implemented with the
.reset operation.

> +
> +static int brcm_rescal_reset_xlate(struct reset_controller_dev *rcdev,
> + const struct of_phandle_args *reset_spec)
> +{
> + /* This is needed if #reset-cells == 0. */
> + return 0;
> +}
> +
> +static const struct reset_control_ops brcm_rescal_reset_ops = {
> + .assert = brcm_rescal_reset_assert,
> + .deassert = brcm_rescal_reset_deassert,
> +};
> +
> +static int brcm_rescal_reset_probe(struct platform_device *pdev)
> +{
> + struct brcm_rescal_reset *data;
> + struct resource *res;
> +
> + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + data->base = devm_ioremap_resource(&pdev->dev, res);
> +
> + if (IS_ERR(data->base))
> + return PTR_ERR(data->base);
> +
> + platform_set_drvdata(pdev, data);
> +
> + data->rcdev.owner = THIS_MODULE;
> + data->rcdev.nr_resets = 1;
> + data->rcdev.ops = &brcm_rescal_reset_ops;
> + data->rcdev.of_node = pdev->dev.of_node;
> + data->rcdev.of_xlate = brcm_rescal_reset_xlate;
> + data->dev = &pdev->dev;
> +
> + return devm_reset_controller_register(&pdev->dev, &data->rcdev);
> +}
> +
> +static const struct of_device_id brcm_rescal_reset_of_match[] = {
> + { .compatible = "brcm,bcm7216-pcie-sata-rescal" },
> + { },
> +};
> +MODULE_DEVICE_TABLE(of, brcm_rescal_reset_of_match);
> +
> +static struct platform_driver brcm_rescal_reset_driver = {
> + .probe = brcm_rescal_reset_probe,
> + .driver = {
> + .name = "brcm-rescal-reset",
> + .of_match_table = brcm_rescal_reset_of_match,
> + }
> +};
> +module_platform_driver(brcm_rescal_reset_driver);
> +
> +MODULE_AUTHOR("Broadcom");
> +MODULE_DESCRIPTION("Broadcom Sata/PCIe rescal reset controller");
> +MODULE_LICENSE("GPL v2");

regards
Philipp

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