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Message-ID: <ff0ee500-8910-32e3-3933-2f9ca0981db3@kernel.org>
Date:   Tue, 15 Aug 2023 13:14:40 +0300
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Subject: Re: [PATCH v4 3/5] net: ti: icss-iep: Add IEP driver
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To:     "Anwar, Md Danish" <a0501179@ti.com>,
        MD Danish Anwar <danishanwar@ti.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Simon Horman <simon.horman@corigine.com>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Richard Cochran <richardcochran@gmail.com>,
        Conor Dooley <conor+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>
Cc:     nm@ti.com, srk@ti.com, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, netdev@vger.kernel.org,
        linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org
References: <20230814100847.3531480-1-danishanwar@ti.com>
 <20230814100847.3531480-4-danishanwar@ti.com>
 <a626c351-2c9b-1136-c31c-63cd695d9499@kernel.org>
 <e54b864a-12b8-0b3e-44a4-81c0e0f4c102@ti.com>
From:   Roger Quadros <rogerq@kernel.org>
In-Reply-To: <e54b864a-12b8-0b3e-44a4-81c0e0f4c102@ti.com>
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On 15/08/2023 13:07, Anwar, Md Danish wrote:
> Hi Roger,
> 
> On 8/15/2023 3:11 PM, Roger Quadros wrote:
>> Hi Danish,
>>
>> On 14/08/2023 13:08, MD Danish Anwar wrote:
>>> From: Roger Quadros <rogerq@ti.com>
>>>
>>> Add a driver for Industrial Ethernet Peripheral (IEP) block of PRUSS to
>>> support timestamping of ethernet packets and thus support PTP and PPS
>>> for PRU ethernet ports.
>>>
>>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>>> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
>>> Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
>>> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
>>> Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
>>> ---
>>>   drivers/net/ethernet/ti/Kconfig          |  11 +
>>>   drivers/net/ethernet/ti/Makefile         |   1 +
>>>   drivers/net/ethernet/ti/icssg/icss_iep.c | 921 +++++++++++++++++++++++
>>>   drivers/net/ethernet/ti/icssg/icss_iep.h |  38 +
>>>   4 files changed, 971 insertions(+)
>>>   create mode 100644 drivers/net/ethernet/ti/icssg/icss_iep.c
>>>   create mode 100644 drivers/net/ethernet/ti/icssg/icss_iep.h
>>>
>>> diff --git a/drivers/net/ethernet/ti/Kconfig b/drivers/net/ethernet/ti/Kconfig
>>> index 63e510b6860f..1af5a90720ec 100644
>>> --- a/drivers/net/ethernet/ti/Kconfig
>>> +++ b/drivers/net/ethernet/ti/Kconfig
>>> @@ -196,4 +196,15 @@ config TI_ICSSG_PRUETH
>>>         to support the Ethernet operation. Currently, it supports Ethernet
>>>         with 1G and 100M link speed.
>>>   +config TI_ICSS_IEP
>>> +    tristate "TI PRU ICSS IEP driver"
>>> +    depends on TI_PRUSS
>>> +    default TI_PRUSS
>>> +    help
>>> +      This driver enables support for the PRU-ICSS Industrial Ethernet
>>> +      Peripheral within a PRU-ICSS subsystem present on various TI SoCs.
>>> +
>>> +      To compile this driver as a module, choose M here. The module
>>> +      will be called icss_iep.
>>> +
>>>   endif # NET_VENDOR_TI
>>> diff --git a/drivers/net/ethernet/ti/Makefile b/drivers/net/ethernet/ti/Makefile
>>> index 9176d79c36e1..34fd7a716ba6 100644
>>> --- a/drivers/net/ethernet/ti/Makefile
>>> +++ b/drivers/net/ethernet/ti/Makefile
>>> @@ -38,3 +38,4 @@ icssg-prueth-y := k3-cppi-desc-pool.o \
>>>             icssg/icssg_mii_cfg.o \
>>>             icssg/icssg_stats.o \
>>>             icssg/icssg_ethtool.o
>>> +obj-$(CONFIG_TI_ICSS_IEP) += icssg/icss_iep.o
>>> diff --git a/drivers/net/ethernet/ti/icssg/icss_iep.c b/drivers/net/ethernet/ti/icssg/icss_iep.c
>>> new file mode 100644
>>> index 000000000000..d123b8ba3f31
>>> --- /dev/null
>>> +++ b/drivers/net/ethernet/ti/icssg/icss_iep.c
>>> @@ -0,0 +1,921 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +
>>> +/* Texas Instruments ICSSG Industrial Ethernet Peripheral (IEP) Driver
>>> + *
>>> + * Copyright (C) 2023 Texas Instruments Incorporated - https://www.ti.com
>>> + *
>>> + */
>>> +
>>> +#include <linux/bitops.h>
>>> +#include <linux/clk.h>
>>> +#include <linux/err.h>
>>> +#include <linux/io.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_platform.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/timekeeping.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/of_irq.h>
>>> +
>>> +#include "icss_iep.h"
>>> +
>>> +#define IEP_MAX_DEF_INC        0xf
>>> +#define IEP_MAX_COMPEN_INC        0xfff
>>> +#define IEP_MAX_COMPEN_COUNT    0xffffff
>>> +
>>> +#define IEP_GLOBAL_CFG_CNT_ENABLE    BIT(0)
>>> +#define IEP_GLOBAL_CFG_DEFAULT_INC_MASK        GENMASK(7, 4)
>>> +#define IEP_GLOBAL_CFG_DEFAULT_INC_SHIFT    4
>>> +#define IEP_GLOBAL_CFG_COMPEN_INC_MASK        GENMASK(19, 8)
>>> +#define IEP_GLOBAL_CFG_COMPEN_INC_SHIFT        8
>>> +
>>> +#define IEP_GLOBAL_STATUS_CNT_OVF    BIT(0)
>>> +
>>> +#define IEP_CMP_CFG_SHADOW_EN        BIT(17)
>>> +#define IEP_CMP_CFG_CMP0_RST_CNT_EN    BIT(0)
>>> +#define IEP_CMP_CFG_CMP_EN(cmp)        (GENMASK(16, 1) & (1 << ((cmp) + 1)))
>>> +
>>> +#define IEP_CMP_STATUS(cmp)        (1 << (cmp))
>>> +
>>> +#define IEP_SYNC_CTRL_SYNC_EN        BIT(0)
>>> +#define IEP_SYNC_CTRL_SYNC_N_EN(n)    (GENMASK(2, 1) & (BIT(1) << (n)))
>>> +
>>> +#define IEP_MIN_CMP    0
>>> +#define IEP_MAX_CMP    15
>>> +
>>> +#define ICSS_IEP_64BIT_COUNTER_SUPPORT        BIT(0)
>>> +#define ICSS_IEP_SLOW_COMPEN_REG_SUPPORT    BIT(1)
>>> +#define ICSS_IEP_SHADOW_MODE_SUPPORT        BIT(2)
>>> +
>>> +#define LATCH_INDEX(ts_index)            ((ts_index) + 6)
>>> +#define IEP_CAP_CFG_CAPNR_1ST_EVENT_EN(n)    BIT(LATCH_INDEX(n))
>>> +#define IEP_CAP_CFG_CAP_ASYNC_EN(n)        BIT(LATCH_INDEX(n) + 10)
>>> +
>>> +enum {
>>> +    ICSS_IEP_GLOBAL_CFG_REG,
>>> +    ICSS_IEP_GLOBAL_STATUS_REG,
>>> +    ICSS_IEP_COMPEN_REG,
>>> +    ICSS_IEP_SLOW_COMPEN_REG,
>>> +    ICSS_IEP_COUNT_REG0,
>>> +    ICSS_IEP_COUNT_REG1,
>>> +    ICSS_IEP_CAPTURE_CFG_REG,
>>> +    ICSS_IEP_CAPTURE_STAT_REG,
>>> +
>>> +    ICSS_IEP_CAP6_RISE_REG0,
>>> +    ICSS_IEP_CAP6_RISE_REG1,
>>> +
>>> +    ICSS_IEP_CAP7_RISE_REG0,
>>> +    ICSS_IEP_CAP7_RISE_REG1,
>>> +
>>> +    ICSS_IEP_CMP_CFG_REG,
>>> +    ICSS_IEP_CMP_STAT_REG,
>>> +    ICSS_IEP_CMP0_REG0,
>>> +    ICSS_IEP_CMP0_REG1,
>>> +    ICSS_IEP_CMP1_REG0,
>>> +    ICSS_IEP_CMP1_REG1,
>>> +
>>> +    ICSS_IEP_CMP8_REG0,
>>> +    ICSS_IEP_CMP8_REG1,
>>> +    ICSS_IEP_SYNC_CTRL_REG,
>>> +    ICSS_IEP_SYNC0_STAT_REG,
>>> +    ICSS_IEP_SYNC1_STAT_REG,
>>> +    ICSS_IEP_SYNC_PWIDTH_REG,
>>> +    ICSS_IEP_SYNC0_PERIOD_REG,
>>> +    ICSS_IEP_SYNC1_DELAY_REG,
>>> +    ICSS_IEP_SYNC_START_REG,
>>> +    ICSS_IEP_MAX_REGS,
>>> +};
>>> +
>>> +/**
>>> + * struct icss_iep_plat_data - Plat data to handle SoC variants
>>> + * @config: Regmap configuration data
>>> + * @reg_offs: register offsets to capture offset differences across SoCs
>>> + * @flags: Flags to represent IEP properties
>>> + */
>>> +struct icss_iep_plat_data {
>>> +    struct regmap_config *config;
>>> +    u32 reg_offs[ICSS_IEP_MAX_REGS];
>>> +    u32 flags;
>>> +};
>>> +
>>> +struct icss_iep {
>>> +    struct device *dev;
>>> +    void __iomem *base;
>>> +    const struct icss_iep_plat_data *plat_data;
>>> +    struct regmap *map;
>>> +    struct device_node *client_np;
>>> +    unsigned long refclk_freq;
>>> +    int clk_tick_time;    /* one refclk tick time in ns */
>>> +    struct ptp_clock_info ptp_info;
>>> +    struct ptp_clock *ptp_clock;
>>> +    struct mutex ptp_clk_mutex;    /* PHC access serializer */
>>> +    spinlock_t irq_lock; /* CMP IRQ vs icss_iep_ptp_enable access */
>>> +    u32 def_inc;
>>> +    s16 slow_cmp_inc;
>>> +    u32 slow_cmp_count;
>>> +    const struct icss_iep_clockops *ops;
>>> +    void *clockops_data;
>>> +    u32 cycle_time_ns;
>>> +    u32 perout_enabled;
>>> +    bool pps_enabled;
>>> +    int cap_cmp_irq;
>>> +    u64 period;
>>> +    u32 latch_enable;
>>> +};
>>> +
>>
>> Where is the comment you agreed to add on why we are using readl/writel
>> instead of regmap in certain areas?
>>
> 
> We agreed to add comment on why we are using readl/writel instead of regmap in the documentation of the readl / writel helper APIs (icss_iep_readl / writel ). But Andrew asked me to drop those helper APIs, so I dropped them. Now no helper APIs are there and we are directly using readl / writel in total 8 places. Previously with the helper APIs, there was a way to document the use of readl / writel before the declaration of heper APIs. Now with no helper APIs, I couldn't find a good place to add this documentation as all 8 instances using readl / writel seems similar. So I dropped it.

Please limit your reply to around 80 columns wide.
https://people.kernel.org/tglx/notes-about-netiquette

You don't have to put the comment everywhere you use readl/writel
but you need to put it at least once hopefully just before icss_iep_gettime()
so future readers of this code know the reasoning why we are not
using regmap API throughout.

> 
>>> +/**
>>> + * icss_iep_get_count_hi() - Get the upper 32 bit IEP counter
>>> + * @iep: Pointer to structure representing IEP.
>>> + *
>>> + * Return: upper 32 bit IEP counter
>>> + */
>>> +int icss_iep_get_count_hi(struct icss_iep *iep)
>>> +{
>>> +    u32 val = 0;
>>> +
>>> +    if (iep && (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT))
>>> +        val = readl(iep->base + iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG1]);
>>> +
>>> +    return val;
>>> +}
>>> +EXPORT_SYMBOL_GPL(icss_iep_get_count_hi);
>>> +
>>> +/**
>>> + * icss_iep_get_count_low() - Get the lower 32 bit IEP counter
>>> + * @iep: Pointer to structure representing IEP.
>>> + *
>>> + * Return: lower 32 bit IEP counter
>>> + */
>>> +int icss_iep_get_count_low(struct icss_iep *iep)
>>> +{
>>> +    u32 val = 0;
>>> +
>>> +    if (iep)
>>> +        val = readl(iep->base + iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG0]);
>>> +
>>> +    return val;
>>> +}
>>> +EXPORT_SYMBOL_GPL(icss_iep_get_count_low);
>>> +
>>> +/**
>>> + * icss_iep_get_ptp_clock_idx() - Get PTP clock index using IEP driver
>>> + * @iep: Pointer to structure representing IEP.
>>> + *
>>> + * Return: PTP clock index, -1 if not registered
>>> + */
>>> +int icss_iep_get_ptp_clock_idx(struct icss_iep *iep)
>>> +{
>>> +    if (!iep || !iep->ptp_clock)
>>> +        return -1;
>>> +    return ptp_clock_index(iep->ptp_clock);
>>> +}
>>> +EXPORT_SYMBOL_GPL(icss_iep_get_ptp_clock_idx);
>>> +
>>> +static void icss_iep_set_counter(struct icss_iep *iep, u64 ns)
>>> +{
>>> +    if (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT)
>>> +        writel(upper_32_bits(ns), iep->base +
>>> +               iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG1]);
>>> +    writel(upper_32_bits(ns), iep->base + iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG0]);
>>> +}
>>> +
>>> +static void icss_iep_update_to_next_boundary(struct icss_iep *iep, u64 start_ns);
>>> +
>>> +static void icss_iep_settime(struct icss_iep *iep, u64 ns)
>>> +{
>>> +    unsigned long flags;
>>> +
>>> +    if (iep->ops && iep->ops->settime) {
>>> +        iep->ops->settime(iep->clockops_data, ns);
>>> +        return;
>>> +    }
>>> +
>>> +    spin_lock_irqsave(&iep->irq_lock, flags);
>>> +    if (iep->pps_enabled || iep->perout_enabled)
>>> +        writel(0, iep->base + iep->plat_data->reg_offs[ICSS_IEP_SYNC_CTRL_REG]);
>>> +
>>> +    icss_iep_set_counter(iep, ns);
>>> +
>>> +    if (iep->pps_enabled || iep->perout_enabled) {
>>> +        icss_iep_update_to_next_boundary(iep, ns);
>>> +        writel(IEP_SYNC_CTRL_SYNC_N_EN(0) | IEP_SYNC_CTRL_SYNC_EN,
>>> +               iep->base + iep->plat_data->reg_offs[ICSS_IEP_SYNC_CTRL_REG]);
>>> +    }
>>> +    spin_unlock_irqrestore(&iep->irq_lock, flags);
>>> +}
>>> +
>>> +static u64 icss_iep_gettime(struct icss_iep *iep,
>>> +                struct ptp_system_timestamp *sts)
>>> +{
>>> +    u32 ts_hi = 0, ts_lo;
>>> +    unsigned long flags;
>>> +
>>> +    if (iep->ops && iep->ops->gettime)
>>> +        return iep->ops->gettime(iep->clockops_data, sts);
>>> +
>>> +    /* use local_irq_x() to make it work for both RT/non-RT */
>>> +    local_irq_save(flags);
>>> +
>>> +    /* no need to play with hi-lo, hi is latched when lo is read */
>>> +    ptp_read_system_prets(sts);
>>> +    ts_lo = readl(iep->base + iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG0]);
>>> +    ptp_read_system_postts(sts);
>>> +    if (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT)
>>> +        ts_hi = readl(iep->base + iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG1]);
>>> +
>>> +    local_irq_restore(flags);
>>> +
>>> +    return (u64)ts_lo | (u64)ts_hi << 32;
>>> +}
>>> +
>>> +static void icss_iep_enable(struct icss_iep *iep)
>>> +{
>>> +    regmap_update_bits(iep->map, ICSS_IEP_GLOBAL_CFG_REG,
>>> +               IEP_GLOBAL_CFG_CNT_ENABLE,
>>> +               IEP_GLOBAL_CFG_CNT_ENABLE);
>>> +}
>>> +
>> <snip>
>>
> 

-- 
cheers,
-roger