[PATCH 04/10] timer: cadence-ttc: Add timer_early functions
Michal Simek
michal.simek at amd.com
Wed Oct 5 08:59:15 CEST 2022
Hi,
On 10/4/22 18:29, Simon Glass wrote:
> Hi,
>
> On Tue, 4 Oct 2022 at 05:50, Michal Simek <michal.simek at amd.com> wrote:
>>
>> Hi Stefan,
>>
>> On 9/30/22 15:45, Stefan Roese wrote:
>>> Hi Michal,
>>>
>>> On 30.09.22 14:02, Michal Simek wrote:
>>>> Hi Simon and Stefan,
>>>>
>>>> On 9/28/22 03:54, Simon Glass wrote:
>>>>>> Hi Simon,
>>>>>> Hi Michal,
>>>>>>
>>>>>> On 25.09.22 16:15, Simon Glass wrote:
>>>>>>> Hi Stefan,
>>>>>>>
>>>>>>> On Wed, 21 Sept 2022 at 08:06, Stefan Roese <sr at denx.de> wrote:
>>>>>>>>
>>>>>>>> Currently this timer driver provides timer_get_boot_us() to support the
>>>>>>>> BOOTSTAGE functionality. This patch adds the timer_early functions so
>>>>>>>> that the "normal" timer functions can be used, when CONFIG_TIMER_EARLY
>>>>>>>> is enabled.
>>>>>>>>
>>>>>>>> timer_get_boot_us() will get removed in a follow-up patch, once the
>>>>>>>> BOOTSTAGE interface is migrated to timer_get_us().
>>>>>>>>
>>>>>>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>>>>>>> Cc: Michal Simek <michal.simek at xilinx.com>
>>>>>>>> ---
>>>>>>>> drivers/timer/cadence-ttc.c | 25 +++++++++++++++++++++++++
>>>>>>>> 1 file changed, 25 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/timer/cadence-ttc.c b/drivers/timer/cadence-ttc.c
>>>>>>>> index 2eff45060ad6..e26c7923a140 100644
>>>>>>>> --- a/drivers/timer/cadence-ttc.c
>>>>>>>> +++ b/drivers/timer/cadence-ttc.c
>>>>>>>> @@ -58,6 +58,31 @@ ulong timer_get_boot_us(void)
>>>>>>>> }
>>>>>>>> #endif
>>>>>>>>
>>>>>>>> +unsigned long notrace timer_early_get_rate(void)
>>>>>>>> +{
>>>>>>>> + return 1;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +u64 notrace timer_early_get_count(void)
>>>>>>>> +{
>>>>>>>> + u64 ticks = 0;
>>>>>>>> + u32 rate = 1;
>>>>>>>> + u64 us;
>>>>>>>> + int ret;
>>>>>>>> +
>>>>>>>> + ret = dm_timer_init();
>>>>>>>
>>>>>>> I don't think you can call this if you want to support bootstage,
>>>>>>> since driver model may not be inited.
>>>>>>
>>>>>> Yes, thanks for noticing. Still, this code is copied from the original
>>>>>> timer_get_boot_us() function in this driver. Which also has problems
>>>>>> with early timer access AFAICT.
>>>>>
>>>>> Yes, good point.
>>>>>
>>>>> Reviewed-by: Simon Glass <sjg at chromium.org>
>>>>
>>>> I looked at it and kind of interesting code. For getting this working with
>>>> this whole series if ttc gets u-boot,dm-pre-reloc everthing is working fine.
>>>
>>> Yes, makes sense that this is needed.
>>>
>>>> diff --git a/arch/arm/dts/zynqmp-r5.dts b/arch/arm/dts/zynqmp-r5.dts
>>>> index a72172ef2ea4..8059931f2162 100644
>>>> --- a/arch/arm/dts/zynqmp-r5.dts
>>>> +++ b/arch/arm/dts/zynqmp-r5.dts
>>>> @@ -56,6 +56,7 @@
>>>>
>>>> ttc0: timer at ff110000 {
>>>> compatible = "cdns,ttc";
>>>> + u-boot,dm-pre-reloc;
>>>> status = "okay";
>>>> reg = <0xff110000 0x1000>;
>>>> timer-width = <32>;
>>>>
>>>> What I see based on behavior. Every bootstage call is asking for
>>>> timer_early_get_count() and because dm_timer_init() is failing 0 is returned.
>>>>
>>>> Inside initf_dm() dm_init_and_scan() is called and initialized timer uclass
>>>> also with timer instance. With u-boot,dm-pre-reloc also cadence timer driver.
>>>> On the next dm_timer_init() gd->timer is initialized and value is returned and
>>>> initf_dm() passes.
>>>
>>> This "early" implementation of the counter is broken, as you have
>>> noticed above. Resulting in timer functions only returning valid
>>> values after dm_timer_init(). This timer driver needs re-written
>>> early_timer functions, that will return proper timer values even in
>>> the early boot phase. Please take a look at e.g. rockchip_timer.c,
>>> perhaps something similar works for the cadence timer driver as well?
>>
>> I looked at it and there is a code when OF_REAL is enabled. If not then 0 is
>> returned. That's why I can't see any difference between rockchip and cadence
>> when OF_REAL is not enabled.
>>
>> And not sure how this is working in rockchip case. Who is starting timer in
>> their case? I see start when probe happens but after it dm_timer_init() should
>> return 0 and value can be obtained.
>>
>>>
>>>> Here is the log and output from bootstage.
>>>>
>>>> U-Boot 2022.10-rc5-00130-g1be5bed207c9 (Sep 30 2022 - 14:00:08 +0200)
>>>>
>>>> Model: Xilinx ZynqMP R5
>>>> DRAM: 512 MiB
>>>> Core: 7 devices, 7 uclasses, devicetree: embed
>>>> MMC:
>>>> Loading Environment from nowhere... OK
>>>> In: serial at ff010000
>>>> Out: serial at ff010000
>>>> Err: serial at ff010000
>>>> Net: No ethernet found.
>>>> ZynqMP r5> dm tree
>>>> Class Index Probed Driver Name
>>>> -----------------------------------------------------------
>>>> root 0 [ + ] root_driver root_driver
>>>> clk 0 [ + ] fixed_clock |-- clk100
>>>> simple_bus 0 [ + ] simple_bus |-- amba
>>>> timer 0 [ + ] cadence_ttc | |-- timer at ff110000
>>>> serial 0 [ + ] serial_zynq | `-- serial at ff010000
>>>> bootstd 0 [ ] bootstd_drv `-- bootstd
>>>> bootmeth 0 [ ] bootmeth_distro `-- distro
>>>> ZynqMP r5> bootstage report
>>>> Timer summary in microseconds (8 records):
>>>> Mark Elapsed Stage
>>>> 0 0 reset
>>>> 0 0 board_init_f
>>>> 0 0 dm_f
>>>> 0 0 dm_r
>>>> 16,319 16,319 eth_common_init
>>>> 18,061 1,742 main_loop
>>>> 18,281 220 cli_loop
>>>> 29,249 10,968 board_init_r
>>>>
>>>> Accumulated time:
>>>
>>> Take a look at sandbox - here you will get proper early timing values
>>> as well:
>>
>> I expect early functions are called before DM is ready that's why to get it work
>> that early we would have to start timer on the first call of early function.
>> It is definitely doable but is it worth to do it?
>>
>> Is there any other use case where early timer counts are needed other then
>> bootstage?
>
> Here is how it should work, I think:
>
> static void notrace ensure_timer_setup(void)
> {
> // set up the timer if not already done
> // avoid using any DM functions
> }
>
> static u64 xx_get_count(void)
> {
> // read and return the timer counter
> }
>
> u64 notrace timer_early_get_count(void)
> {
> ensure_timer_setup();
> return xxx_get_count();
> }
>
> static u64 xx_timer_get_count(struct udevice *dev)
> {
> return xxx_get_count();
> }
>
> int xxx_timer_probe(struct udevice *dev)
> {
> ensure_timer_setup()\;
>
> return 0;
> }
ok this is clear and understandable.
As far as I see the only information we need is to have address where timer is.
Rockchip and uclass drivers are using tick-timer when multiple timers are
described in DT.
That's why for systems with only one timer this property is not needed.
Also this option is enabled only when OF_REAL is enabled.
When it is clear which link to use for getting address from DT or via DM we can
change drivers pretty easily.
Thanks,
Michal
More information about the U-Boot
mailing list