On 11/08/23 8:54 pm, Andrew Davis wrote:
> On 8/10/23 6:50 AM, Md Danish Anwar wrote:
>> Hi Andrew,
>>
>> On 09/08/23 8:30 pm, Andrew Davis wrote:
>>> On 8/9/23 6:49 AM, MD Danish Anwar wrote:
>>>> From: Roger Quadros <rogerq@xxxxxx>
>>>>
>>>> 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@xxxxxx>
>>>> Signed-off-by: Lokesh Vutla <lokeshvutla@xxxxxx>
>>>> Signed-off-by: Murali Karicheri <m-karicheri2@xxxxxx>
>>>> Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
>>>> Signed-off-by: MD Danish Anwar <danishanwar@xxxxxx>
>>>> ---
>>>> drivers/net/ethernet/ti/Kconfig | 12 +
>>>> drivers/net/ethernet/ti/Makefile | 1 +
>>>> drivers/net/ethernet/ti/icssg/icss_iep.c | 935 +++++++++++++++++++++++
>>>> drivers/net/ethernet/ti/icssg/icss_iep.h | 38 +
>>>> 4 files changed, 986 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..88b5b1b47779 100644
>>>> --- a/drivers/net/ethernet/ti/Kconfig
>>>> +++ b/drivers/net/ethernet/ti/Kconfig
>>>> @@ -186,6 +186,7 @@ config CPMAC
>>>> config TI_ICSSG_PRUETH
>>>> tristate "TI Gigabit PRU Ethernet driver"
>>>> select PHYLIB
>>>> + select TI_ICSS_IEP
>>>
>>> Why not save selecting this until you add its use in the ICSSG_PRUETH driver in
>>> the next patch.
>>>
>>
>> The next patch is only adding changes to icssg-prueth .c /.h files. This patch
>> is adding changes to Kconfig and the Makefile. To keep it that way selecting
>> this is added in this patch. No worries, I will move this to next patch.
>>
>>> [...]
>>>
>>>> +
>>>> +static u32 icss_iep_readl(struct icss_iep *iep, int reg)
>>>> +{
>>>> + return readl(iep->base + iep->plat_data->reg_offs[reg]);
>>>> +}
>>>
>>> Do these one line functions really add anything? Actually why
>>> not use the regmap you have here.
>>
>> These one line functions are not really adding anything but they are acting as
>> a wrapper around readl /writel and providing some sort of encapsulation as
>> directly calling readl will result in a little complicated code.
>>
>> /* WIth One line function */
>> ts_lo = icss_iep_readl(iep, ICSS_IEP_COUNT_REG0);
>>
>> /* Without one line function */
>> ts_lo = readl(iep->base, iep->plat_data->reg_offs[ICSS_IEP_COUNT_REG0]);
>>
>> Previously regmap was used in this driver. But in older commit [1] in
>> 5.10-ti-linux-kernel (Before I picked the driver for upstream) it got changed
>> to readl / writel stating that regmap_read / write is too slow. IEP is time
>> sensitive and needs faster read and write, probably because of this they
>> changed it.
>>
>
> Sounds like you only need direct register access for time sensitive
> gettime/settime functions, if that is the only place writel()/readl() is
> needed just drop the helper and use directly in that one spot.
>
In total both icss_iep_readl() and writel() are used 4 time each. All related
to gettime / settime. This is the only place where these helper APIs are used.
I will drop these helper apis and used readl / writel directly.
>>>
>>> [...]
>>>
>>>> +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);
>>>
>>> Have you looked into regmap_fields?
>>>
>>
>> No I hadn't. But now I looked into regmap_fields, seems to be another way to
>> update the bits, instead of passing mask and value, regmap_filed_read / write
>> only takes the value. But for that we will need to create a regmap field. If
>> you want me to switch to regmap_fields instead of regmap_update_bits I can make
>> the changes. But I am fine with regmap_update_bits().
>>
>
> I'm suggesting regmap fields as I have used it several times and it resulted
> in greatly improved readability. Yes you will need a regmap field table, but
> that is the best part, it lets you put all your bit definitions in one spot
> that can match 1:1 with the datasheet, much easier to check for correctness
> than if the bit usages are all spread out in the driver.
>
> I won't insist on you converting this driver to use it today, but I do recommend
> you at least give it a shot for your own learning.
>
Sure Andrew. For now I will keep it as regmap_update_bits(). I will look into
regmap_fields for my own learning.
> Andrew
>
>>> [...]
>>>
>>>> +
>>>> + if (!!(iep->latch_enable & BIT(index)) == !!on)
>>>> + goto exit;
>>>> +
>>>
>>> There has to be a better way to write this logic..
>>>
>>> [...]
>>>
>>>> +
>>>> +static const struct of_device_id icss_iep_of_match[];
>>>> +
>>>
>>> Why the forward declaration?
>>
>> I will remove this, I don't see any reason for this.
>>
>>>
>>>> +static int icss_iep_probe(struct platform_device *pdev)
>>>> +{
>>>> + struct device *dev = &pdev->dev;
>>>> + struct icss_iep *iep;
>>>> + struct clk *iep_clk;
>>>> +
>>>> + iep = devm_kzalloc(dev, sizeof(*iep), GFP_KERNEL);
>>>> + if (!iep)
>>>> + return -ENOMEM;
>>>> +
>>>> + iep->dev = dev;
>>>> + iep->base = devm_platform_ioremap_resource(pdev, 0);
>>>> + if (IS_ERR(iep->base))
>>>> + return -ENODEV;
>>>> +
>>>> + iep_clk = devm_clk_get(dev, NULL);
>>>> + if (IS_ERR(iep_clk))
>>>> + return PTR_ERR(iep_clk);
>>>> +
>>>> + iep->refclk_freq = clk_get_rate(iep_clk);
>>>> +
>>>> + iep->def_inc = NSEC_PER_SEC / iep->refclk_freq; /* ns per clock
>>>> tick */
>>>> + if (iep->def_inc > IEP_MAX_DEF_INC) {
>>>> + dev_err(dev, "Failed to set def_inc %d. IEP_clock is too slow to be
>>>> supported\n",
>>>> + iep->def_inc);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + iep->plat_data = of_device_get_match_data(dev);
>>>
>>> Directly using of_*() functions is often wrong, try just
>>> device_get_match_data().
>>>
>>
>> Sure. I will change to device_get_match_data().
>>
>>> [...]
>>>
>>>> +static struct platform_driver icss_iep_driver = {
>>>> + .driver = {
>>>> + .name = "icss-iep",
>>>> + .of_match_table = of_match_ptr(icss_iep_of_match),
>>>
>>> This driver cannot work without OF, using of_match_ptr() is not needed.
>>>
>>
>> Sure, I will drop of_match_ptr().
>>
>>> Andrew
>>
>>
>> For reading and updating registers, we can have
>> 1. icss_iep_readl / writel and regmap_update_bits() OR
>> 2. regmap_read / write and regmap_update_bits() OR
>> 3. icss_iep_readl / writel and regmap_fields OR
>> 4. regmap_read / write and regmap_fields
>>
>>
>> Currently we are using 1. Please let me know if you are fine with this and I
>> can continue using 1. If not, please let me know your recommendation out of
>> this 4.
>>
>> [1]
>> https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/?h=linux-5.10.y&id=f4f45bf71cad5be232536d63a0557d13a7eed162
>>
--
Thanks and Regards,
Danish.
