Re: [PATCH 2/8] soc: ti: add initial PRM driver with reset control support

[Suman Anna <s-anna@ti.com>]

Hi Tero,

On 8/19/19 4:32 AM, Tero Kristo wrote:
> On 08/08/2019 08:26, Keerthy wrote:
>>
>>
>> On 07/08/19 1:18 PM, Tero Kristo wrote:
>>> Add initial PRM (Power and Reset Management) driver for TI OMAP class
>>> SoCs. Initially this driver only supports reset control, but can be
>>> extended to support rest of the functionality, like powerdomain
>>> control, PRCM irq support etc.
>>>
>>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>>> ---
>>>   arch/arm/mach-omap2/Kconfig |   1 +
>>>   drivers/soc/ti/Makefile     |   1 +
>>>   drivers/soc/ti/omap_prm.c   | 216
>>> ++++++++++++++++++++++++++++++++++++++++++++
>>>   3 files changed, 218 insertions(+)
>>>   create mode 100644 drivers/soc/ti/omap_prm.c
>>>
>>> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
>>> index fdb6743..42ad063 100644
>>> --- a/arch/arm/mach-omap2/Kconfig
>>> +++ b/arch/arm/mach-omap2/Kconfig
>>> @@ -109,6 +109,7 @@ config ARCH_OMAP2PLUS
>>>       select TI_SYSC
>>>       select OMAP_IRQCHIP
>>>       select CLKSRC_TI_32K
>>> +    select RESET_CONTROLLER

Use ARCH_HAS_RESET_CONTROLLER instead.

>>>       help
>>>         Systems based on OMAP2, OMAP3, OMAP4 or OMAP5
>>> diff --git a/drivers/soc/ti/Makefile b/drivers/soc/ti/Makefile
>>> index b3868d3..788b5cd 100644
>>> --- a/drivers/soc/ti/Makefile
>>> +++ b/drivers/soc/ti/Makefile
>>> @@ -6,6 +6,7 @@ obj-$(CONFIG_KEYSTONE_NAVIGATOR_QMSS)    += knav_qmss.o
>>>   knav_qmss-y := knav_qmss_queue.o knav_qmss_acc.o
>>>   obj-$(CONFIG_KEYSTONE_NAVIGATOR_DMA)    += knav_dma.o
>>>   obj-$(CONFIG_AMX3_PM)            += pm33xx.o
>>> +obj-$(CONFIG_ARCH_OMAP2PLUS)        += omap_prm.o
>>>   obj-$(CONFIG_WKUP_M3_IPC)        += wkup_m3_ipc.o
>>>   obj-$(CONFIG_TI_SCI_PM_DOMAINS)        += ti_sci_pm_domains.o
>>>   obj-$(CONFIG_TI_SCI_INTA_MSI_DOMAIN)    += ti_sci_inta_msi.o
>>> diff --git a/drivers/soc/ti/omap_prm.c b/drivers/soc/ti/omap_prm.c
>>> new file mode 100644
>>> index 0000000..7c89eb8
>>> --- /dev/null
>>> +++ b/drivers/soc/ti/omap_prm.c
>>> @@ -0,0 +1,216 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * OMAP2+ PRM driver
>>> + *
>>> + * Copyright (C) 2019 Texas Instruments Incorporated -
>>> http://www.ti.com/
>>> + *    Tero Kristo <t-kristo@ti.com>
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/module.h>
>>> +#include <linux/device.h>
>>> +#include <linux/io.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/reset-controller.h>
>>> +#include <linux/delay.h>
>>> +
>>> +struct omap_rst_map {
>>> +    s8 rst;
>>> +    s8 st;
>>> +};
>>> +
>>> +struct omap_prm_data {
>>> +    u32 base;
>>> +    const char *name;
>>> +    u16 pwstctrl;
>>> +    u16 pwstst;
>>> +    u16 rstctl;

Minor nit, can you use rstctrl instead here so that it is in sync with
the other variables and with the register names used in TRM.

>>> +    u16 rstst;
>>> +    struct omap_rst_map *rstmap;
>>> +    u8 flags;
>>> +};
>>> +
>>> +struct omap_prm {
>>> +    const struct omap_prm_data *data;
>>> +    void __iomem *base;
>>> +};
>>> +
>>> +struct omap_reset_data {
>>> +    struct reset_controller_dev rcdev;
>>> +    struct omap_prm *prm;
>>> +};
>>> +
>>> +#define to_omap_reset_data(p) container_of((p), struct
>>> omap_reset_data, rcdev)
>>> +
>>> +#define OMAP_MAX_RESETS        8
>>> +#define OMAP_RESET_MAX_WAIT    10000
>>> +
>>> +#define OMAP_PRM_NO_RSTST    BIT(0)
>>> +
>>> +static const struct of_device_id omap_prm_id_table[] = {
>>> +    { },
>>> +};
>>
>> This table is blank and we are doing of_match_device against it.
> 
> Yes, it gets populated with other patches in series, one entry per soc.
> 
>>
>>> +
>>> +static int omap_reset_status(struct reset_controller_dev *rcdev,
>>> +                 unsigned long id)
>>> +{
>>> +    struct omap_reset_data *reset = to_omap_reset_data(rcdev);
>>> +    u32 v;
>>> +
>>> +    v = readl_relaxed(reset->prm->base + reset->prm->data->rstst);
>>> +    v &= 1 << id;
>>> +    v >>= id;
>>> +
>>> +    return v;
>>> +}
>>> +
>>> +static int omap_reset_assert(struct reset_controller_dev *rcdev,
>>> +                 unsigned long id)
>>> +{
>>> +    struct omap_reset_data *reset = to_omap_reset_data(rcdev);
>>> +    u32 v;
>>> +
>>> +    /* assert the reset control line */
>>> +    v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
>>> +    v |= 1 << id;
>>> +    writel_relaxed(v, reset->prm->base + reset->prm->data->rstctl);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static int omap_reset_get_st_bit(struct omap_reset_data *reset,
>>> +                 unsigned long id)
>>> +{
>>> +    struct omap_rst_map *map = reset->prm->data->rstmap;
>>> +
>>> +    while (map && map->rst >= 0) {
>>> +        if (map->rst == id)
>>> +            return map->st;
>>> +
>>> +        map++;
>>> +    }
>>> +
>>> +    return id;
>>> +}
>>> +
>>> +/*
>>> + * Note that status will not change until clocks are on, and clocks
>>> cannot be
>>> + * enabled until reset is deasserted. Consumer drivers must check
>>> status
>>> + * separately after enabling clocks.
>>> + */
>>> +static int omap_reset_deassert(struct reset_controller_dev *rcdev,
>>> +                   unsigned long id)
>>> +{
>>> +    struct omap_reset_data *reset = to_omap_reset_data(rcdev);
>>> +    u32 v;
>>> +    int st_bit = id;

No need to initialize this, will always get overwritten below.

>>> +    bool has_rstst;
>>> +
>>> +    /* check the current status to avoid de-asserting the line twice */
>>> +    v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
>>> +    if (!(v & BIT(id)))
>>> +        return -EEXIST;
>>> +
>>> +    has_rstst = !(reset->prm->data->flags & OMAP_PRM_NO_RSTST);
>>> +
>>> +    if (has_rstst) {
>>> +        st_bit = omap_reset_get_st_bit(reset, id);
>>> +
>>> +        /* Clear the reset status by writing 1 to the status bit */
>>> +        v = readl_relaxed(reset->prm->base + reset->prm->data->rstst);
>>> +        v |= 1 << st_bit;
>>> +        writel_relaxed(v, reset->prm->base + reset->prm->data->rstst);
>>> +    }
>>> +
>>> +    /* de-assert the reset control line */
>>> +    v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
>>> +    v &= ~(1 << id);
>>> +    writel_relaxed(v, reset->prm->base + reset->prm->data->rstctl);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct reset_control_ops omap_reset_ops = {
>>> +    .assert        = omap_reset_assert,
>>> +    .deassert    = omap_reset_deassert,
>>> +    .status        = omap_reset_status,
>>> +};
>>> +
>>> +static int omap_prm_reset_probe(struct platform_device *pdev,
>>> +                struct omap_prm *prm)

Call this omap_prm_reset_init or something similar to avoid confusion.

>>> +{
>>> +    struct omap_reset_data *reset;
>>> +
>>> +    /*
>>> +     * Check if we have resets. If either rstctl or rstst is
>>> +     * non-zero, we have reset registers in place. Additionally
>>> +     * the flag OMAP_PRM_NO_RSTST implies that we have resets.
>>> +     */
>>> +    if (!prm->data->rstctl && !prm->data->rstst &&
>>> +        !(prm->data->flags & OMAP_PRM_NO_RSTST))
>>> +        return 0;
>>> +
>>> +    reset = devm_kzalloc(&pdev->dev, sizeof(*reset), GFP_KERNEL);
>>> +    if (!reset)
>>> +        return -ENOMEM;
>>> +
>>> +    reset->rcdev.owner = THIS_MODULE;
>>> +    reset->rcdev.ops = &omap_reset_ops;
>>> +    reset->rcdev.of_node = pdev->dev.of_node;
>>> +    reset->rcdev.nr_resets = OMAP_MAX_RESETS;

Suggest adding a number of resets to prm->data, and using it so that we
don't even entertain any resets beyond the actual number of resets.

You actually seem to be using the bit-position directly in client data
instead of a reset number. I am not sure if this is accepted practice
with reset controllers, do you incur any memory wastage?

>>> +
>>> +    reset->prm = prm;
>>> +
>>> +    return devm_reset_controller_register(&pdev->dev, &reset->rcdev);
>>> +}
>>> +
>>> +static int omap_prm_probe(struct platform_device *pdev)
>>> +{
>>> +    struct resource *res;
>>> +    const struct omap_prm_data *data;
>>> +    struct omap_prm *prm;
>>> +    const struct of_device_id *match;
>>> +
>>> +    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> +    if (!res)
>>> +        return -ENODEV;
>>> +
>>> +    match = of_match_device(omap_prm_id_table, &pdev->dev);
>>> +    if (!match)
>>> +        return -ENOTSUPP;

Use of_device_get_match_data() instead to do both match and get the
data. That can perhaps be the first block.

>>> +
>>> +    prm = devm_kzalloc(&pdev->dev, sizeof(*prm), GFP_KERNEL);
>>> +    if (!prm)
>>> +        return -ENOMEM;

Perhaps move the allocate after the match check to streamline.

>>> +
>>> +    data = match->data;
>>> +
>>> +    while (data->base != res->start) {
>>> +        if (!data->base)
>>> +            return -EINVAL;
>>> +        data++;
>>> +    }
>>> +
>>> +    prm->data = data;
>>> +
>>> +    prm->base = devm_ioremap_resource(&pdev->dev, res);
>>> +    if (!prm->base)
>>> +        return -ENOMEM;
>>> +
>>> +    return omap_prm_reset_probe(pdev, prm);
>>> +}
>>> +
>>> +static struct platform_driver omap_prm_driver = {
>>> +    .probe = omap_prm_probe,
>>> +    .driver = {
>>> +        .name        = KBUILD_MODNAME,
>>> +        .of_match_table    = omap_prm_id_table,
>>> +    },
>>> +};
>>> +builtin_platform_driver(omap_prm_driver);
>>> +
>>> +MODULE_ALIAS("platform:prm");

Drop this and use MODULE_DEVICE_TABLE instead on omap_prm_id_table if
retaining, but I don't think these need to be defined.

regards
Suman

>>> +MODULE_LICENSE("GPL v2");
>>> +MODULE_DESCRIPTION("omap2+ prm driver");
>>
>> It is a builtin_platform_driver so do we need the MODULE*?
> 
> Well, thats debatable, however some existing drivers do introduce this
> even if they are builtin.
> 
> -Tero
> -- 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki


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