[PATCH v2 1/1] timer: imx-gpt: Add timer support for i.MX SoCs family
Giulio Benetti
giulio.benetti at benettiengineering.com
Wed Feb 10 21:09:02 CET 2021
Hi Jesse,
I re-add all people and ML in Cc so they can follow. Next time reply to all.
On 2/10/21 8:00 PM, Jesse Taube wrote:
>
> On 2/10/21 12:49 PM, Giulio Benetti wrote:
>> On 2/10/21 1:04 AM, Jesse Taube wrote:
>>> This timer driver is using GPT Timer (General Purpose Timer)
>>> available on almost all i.MX SoCs family.
>>> Since this driver is only meant to provide u-boot's timer and
>>> counter, and most of the i.MX* SoCs use a 24Mhz crystal, let's only
>>> deal with that specific source.
>>
>> We have a problem with columns on commit log, they shouldn't be longer
>> than 72 cols, so please check the editor you're using for commit log
>> writing and set 72 cols costrains. I use nano and you only need to set
>> in .gitconfig under [core]:
>> editor = nano -b -r 72
>>
>> This way nano automatically put a CR.
>>
>>>
>>> Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
>>> Signed-off-by: Jesse Taube <mr.bossman075 at gmail.com>
>>>
>>> ---
>>> drivers/timer/Kconfig | 7 ++
>>> drivers/timer/Makefile | 1 +
>>> drivers/timer/imx-gpt-timer.c | 132 ++++++++++++++++++++++++++++++++++
>>> 3 files changed, 140 insertions(+)
>>> create mode 100644 drivers/timer/imx-gpt-timer.c
>>>
>>> diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
>>> index 80743a2551..ee81dfa776 100644
>>> --- a/drivers/timer/Kconfig
>>> +++ b/drivers/timer/Kconfig
>>> @@ -227,4 +227,11 @@ config MCHP_PIT64B_TIMER
>>> Select this to enable support for Microchip 64-bit periodic
>>> interval timer.
>>> +config IMX_GPT_TIMER
>>> + bool "NXP i.MX GPT timer support"
>>> + depends on TIMER
>>> + help
>>> + Select this to enable support for the timer found on
>>> + NXP i.MX devices.
>>> +
>>> endmenu
>>> diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
>>> index eb5c48cc6c..e214ba7268 100644
>>> --- a/drivers/timer/Makefile
>>> +++ b/drivers/timer/Makefile
>>> @@ -25,3 +25,4 @@ obj-$(CONFIG_STM32_TIMER) += stm32_timer.o
>>> obj-$(CONFIG_X86_TSC_TIMER) += tsc_timer.o
>>> obj-$(CONFIG_MTK_TIMER) += mtk_timer.o
>>> obj-$(CONFIG_MCHP_PIT64B_TIMER) += mchp-pit64b-timer.o
>>> +obj-$(CONFIG_IMX_GPT_TIMER) += imx-gpt-timer.o
>>> diff --git a/drivers/timer/imx-gpt-timer.c
>>> b/drivers/timer/imx-gpt-timer.c
>>> new file mode 100644
>>> index 0000000000..58c37db300
>>> --- /dev/null
>>> +++ b/drivers/timer/imx-gpt-timer.c
>>> @@ -0,0 +1,132 @@
>>> +// SPDX-License-Identifier: GPL-2.0+
>>> +/*
>>> + * Copyright (C) 2020
>>> + * Author(s): Giulio Benetti <giulio.benetti at benettiengineering.com>
>>> + */
>>> +
>>> +#include <common.h>
>>> +#include <clk.h>
>>> +#include <dm.h>
>>> +#include <fdtdec.h>
>>> +#include <timer.h>
>>> +#include <dm/device_compat.h>
>>> +
>>> +#include <asm/io.h>
>>> +
>>> +#define GPT_CR_SWR 0x00008000
>>> +#define GPT_CR_CLKSRC 0x000001C0
>>> +#define GPT_CR_EN_24M 0x00004000
>>> +#define GPT_CR_EN 0x00000001
>>> +#define GPT_PR_PRESCALER 0x00000FFF
>>> +#define GPT_PR_PRESCALER24M 0x0000F000
>>
>> Here ^^^ and
>>
>>> +#define NO_CLOCK (0)
>>> +#define IPG_CLK (1 << 6)
>>> +#define IPG_CLK_HF (2 << 6)
>>> +#define IPG_EXT (3 << 6)
>>> +#define IPG_CLK_32K (4 << 6)
>>> +#define IPG_CLK_24M (5 << 6)
>> here you still have different tab numbers. Enable in your editor the
>> option to show whitespaces and tabs, that way everything it easier.
> I still don't exactly understand what you mean here. Should I press tab
> 3 times exactly instead of making the values line up.
You need to check using an editor with whitespaces and tabs options
enabled and tabs set to 8 spaces how that code looks like.
> In the commit log
> it seems to change weirdly because of the '+' in front of the define.
Here it is the same, this should be due to the editor you use for commit
log.
>>> +
>>> +struct imx_gpt_timer_regs {
>>> + u32 cr;
>>> + u32 pr;
>>> + u32 sr;
>>> + u32 ir;
>>> + u32 ocr1;
>>> + u32 ocr2;
>>> + u32 ocr3;
>>> + u32 icr1;
>>> + u32 icr2;
>>> + u32 cnt;
>>> +};
>>> +
>>> +struct imx_gpt_timer_priv {
>>> + struct imx_gpt_timer_regs *base;
>>> +};
>>> +
>>> +static u64 imx_gpt_timer_get_count(struct udevice *dev)
>>> +{
>>> + struct imx_gpt_timer_priv *priv = dev_get_priv(dev);
>>> + struct imx_gpt_timer_regs *regs = priv->base;
>>> +
>>> + return readl(®s->cnt);
>>> +}
>>> +
>>> +static int imx_gpt_timer_probe(struct udevice *dev)
>>> +{
>>> + struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
>>> + struct imx_gpt_timer_priv *priv = dev_get_priv(dev);
>>> + struct imx_gpt_timer_regs *regs;
>>> + struct clk clk;
>>> + fdt_addr_t addr;
>>> + u32 prescaler;
>>> + u32 rate;
>>> + int ret;
>>> +
>>> + addr = dev_read_addr(dev);
>>> + if (addr == FDT_ADDR_T_NONE)
>>> + return -EINVAL;
>>> +
>>> + priv->base = (struct imx_gpt_timer_regs *)addr;
>>> +
>>> + ret = clk_get_by_index(dev, 0, &clk);
>>> + if (ret < 0)
>>> + return ret;
>>> +
>>> + ret = clk_enable(&clk);
>>> + if (ret) {
>>> + dev_err(dev, "Failed to enable clock\n");
>>> + return ret;
>>> + }
>>> +
>>> + regs = priv->base;
>>> +
>>> + /* Reset the timer */
>>> + setbits_le32(®s->cr, GPT_CR_SWR);
>>> +
>>> + /* Wait for timer to finish reset */
>>> + while (readl(®s->cr) & GPT_CR_SWR)
>>> + ;
>>> +
>>> + /* Get timer clock rate */
>>> + rate = clk_get_rate(&clk);
>>
>> clk_get_rate() has a wrong description in include/clk.h saying:
>> "@return clock rate in Hz, or -ve error code."
>>
>> This ^^^ is wrong.
>> If you dig into drivers/clk/clk-uclass.c and look for clk_get_rate(),
>> you will see that it returns 0 on error and > 0 if succesfull.
>>
>> I've just sent a patch for this:
>> https://patchwork.ozlabs.org/project/uboot/patch/20210210173722.4823-1-giulio.benetti@benettiengineering.com/
>>
>>
>>> + if ((int)rate <= 0) {
>>
>> This ^^^^ is a cast trying to solve the problem above but it's
>> not correct. clk_get_rate() returns ulong, not int, so modify "int
>> rate" into "ulong rate".
> Ah this makes sense now.
>>
>>> + dev_err(dev, "Could not get clock rate...\n");
>>> + return -EINVAL;
>>> + }
>>> + /* Only support 24MHz clock */
>>
>> Extend to /* Only support 24MHz crystal clock */ otherwise it seems
>> that every 24Mhz clock is accepted and it's not that way.
>>
>> I don't know a sure way to be bounded to crystal clock, suggestions
>> are welcome.
>>
>>> + if (rate != 24000000UL) {
>>> + dev_err(dev, "Clock rate other than 24MHz not supported...\n");
>>> + return -EINVAL;
>>> + }
>>> + /* We set timer prescaler to obtain a 1MHz timer counter
>>> frequency */
>>> + prescaler = (rate / CONFIG_SYS_HZ_CLOCK) - 1;
>>
>> Here you should check against maximum value of PRESCALER(0xFFF), if
>> prescaler is > 0xFFF then you have to return with error.
>>
>>> + writel(GPT_PR_PRESCALER & prescaler, ®s->pr);
>>> + /* Set timer frequency to 1MHz */
>>> + uc_priv->clock_rate = CONFIG_SYS_HZ_CLOCK;
>>> +
>>> + clrbits_le32(®s->cr, GPT_CR_CLKSRC);
>>> + setbits_le32(®s->cr, IPG_CLK);
>>
>> Here IPG_CLK should be IPG_CLK_24M as discussed previously.
>
> The IPG_CLK_24M needs a different prescaler and a second enable bit.
> This will completely bypass all other clock sources making the check for
> the clock rate useless.
Yes, in the operative way yes, you could also avoid passing clock source
through dts, but this way we check that the right clock source is passed
to dts, and that is the correct way to work I think.
> It will also mean that even if we don't have a
> correct clock source it will work at the correct timing.
Yes if they provide 24Mhz.
I wanted it to be like that at the moment, because a lot of imx SoCs
setup GPT like that. Take a look here:
https://gitlab.denx.de/u-boot/u-boot/-/blob/master/arch/arm/mach-imx/timer.c#L80-99
This way the imx6* and imx7 could add their .compatible to this driver
in the future. If someone will need some specific tweaking then they
would send a patch adding such new DT property, like using 32K source.
But that comes next IMHO, otherwise we should describe entirely GPT
peripheral but what we need at the moment is getting 1ms tick like lot
of other imx SoCs already do.
The other chance would be to treat all the clock sources possibilities,
but, at least for me, to begin this is sufficient and can be improved later.
> I changed it to use only the 24MHz clock and ignore all others,
Ok
> at some
> point it would be nice to have it only as a backup clock if the ccm was
> not configured.
I don't understand what you mean with backup clock can you elaborate more?
Thank you
Best regards
--
Giulio Benetti
Benetti Engineering sas
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