[PATCH v6 0/3] Timer support for ARM Tegra
Thierry Reding
thierry.reding at gmail.com
Thu Jan 26 18:54:03 CET 2023
On Thu, Jan 26, 2023 at 07:08:54PM +0200, Svyatoslav Ryhel wrote:
> чт, 26 січ. 2023 р. о 12:35 Thierry Reding <thierry.reding at gmail.com> пише:
> >
> > On Wed, Jan 25, 2023 at 05:41:08PM +0100, Thierry Reding wrote:
> > > On Tue, Jan 24, 2023 at 08:57:48AM +0200, Svyatoslav Ryhel wrote:
> > > > - ARM: tegra: remap clock_osc_freq for all Tegra family
> > > > Enum clock_osc_freq was designed to use only with T20.
> > > > This patch remaps it to use additional frequencies, added in
> > > > T30+ SoC while maintaining backwards compatibility with T20.
> > > >
> > > > - drivers: timer: add timer driver for ARMv7 based Tegra devices
> > > > Add timer support for T20/T30/T114 and T124 based devices.
> > > > Driver is based on DM, has device tree support and can be
> > > > used on SPL and early boot stage.
> > > >
> > > > - ARM: tegra: include timer as default option
> > > > Enable TIMER as default option for all Tegra devices and
> > > > enable TEGRA_TIMER for TEGRA_ARMV7_COMMON. Additionally
> > > > enable SPL_TIMER if build as SPL part and drop deprecated
> > > > configs from common header.
> > > >
> > > > P. S. I have no arm64 Tegra and according to comment in
> > > > tegra-common.h
> > > > Use the Tegra US timer on ARMv7, but the architected timer on ARMv8.
> > > >
> > > > Svyatoslav Ryhel (3):
> > > > ARM: tegra: remap clock_osc_freq for all Tegra family
> > > > drivers: timer: add timer driver for ARMv7 based Tegra devices
> > > > ARM: tegra: include timer as default option
> > >
> > > This causes a regression on Tegra210 (Jetson TX1). I'm trying to
> > > investigate, but it's complicated by the fact that I'm not getting out
> > > any debug prints, so I suspect the issue is happening quite early.
> >
> > Alright, I managed to make this work on Tegra210 using the following
> > patch on top of this series:
> >
>
> Hello! Thanks for testing this on T210 SoC.
>
> > --- >8 ---
> > diff --git a/arch/arm/dts/tegra210.dtsi b/arch/arm/dts/tegra210.dtsi
> > index a521a43d6cfd..ccb5a927da89 100644
> > --- a/arch/arm/dts/tegra210.dtsi
> > +++ b/arch/arm/dts/tegra210.dtsi
> > @@ -318,7 +318,7 @@
> > };
> >
> > timer at 60005000 {
> > - compatible = "nvidia,tegra210-timer", "nvidia,tegra20-timer";
> > + compatible = "nvidia,tegra210-timer", "nvidia,tegra30-timer", "nvidia,tegra20-timer";
>
> This compatibe should not be needed since the driver will have t210
> compatible included.
Yes, it should be fine to leave this as-is. I had included this before
updating the driver, to get the driver to bind to this. Upstream Linux
doesn't include "nvidia,tegra20-timer", so it only has the compatible
string for Tegra210. I think that's slightly better because the register
interface isn't quite compatible. That's a separate issue and we can do
that in a follow-up patch.
>
> > reg = <0x0 0x60005000 0x0 0x400>;
> > interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>,
> > <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>,
> > diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
> > index cc3f00e50128..b50eec5b8c9b 100644
> > --- a/arch/arm/mach-tegra/Kconfig
> > +++ b/arch/arm/mach-tegra/Kconfig
> > @@ -136,6 +136,7 @@ config TEGRA210
> > select TEGRA_PINCTRL
> > select TEGRA_PMC
> > select TEGRA_PMC_SECURE
> > + select TEGRA_TIMER
> >
> > config TEGRA186
> > bool "Tegra186 family"
> > diff --git a/drivers/timer/tegra-timer.c b/drivers/timer/tegra-timer.c
> > index d2d163cf3fef..235532ba8926 100644
> > --- a/drivers/timer/tegra-timer.c
> > +++ b/drivers/timer/tegra-timer.c
> > @@ -58,17 +58,26 @@ static notrace u64 tegra_timer_get_count(struct udevice *dev)
> > static int tegra_timer_probe(struct udevice *dev)
> > {
> > struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
> > + enum clock_osc_freq freq;
> > u32 usec_config, value;
> >
> > /* Timer rate has to be set unconditionally */
> > uc_priv->clock_rate = TEGRA_TIMER_RATE;
> >
> > + /*
> > + * The microsecond timer runs off of clk_m on Tegra210, and clk_m
> > + * runs at half the OSC, so fake this up.
> > + */
> > + freq = clock_get_osc_freq();
> > + if (freq == CLOCK_OSC_FREQ_38_4)
> > + freq = CLOCK_OSC_FREQ_19_2;
> > +
>
> May you confirm that ALL known T210 devices use 19.2MHz as calibration
> clock for timer?
According to the Tegra210 TRM, the TIMERUS depends on the rate of clk_m
and clk_m is derived from OSC and either divided by 1, 2, 3 or 4. The
TRM goes on to say that:
The expectation is that this CLK_M_DIVISOR will only be changed
once after powering VDD_SOC on in cold boot/LP0 exit path. So
these sequences are verified with an oscillator clock of 38.4
MHz; div2 setting of the CLK_M divisor must be used. The result
is 19.2 MHz clk_m.
And then it says:
Note: Div2 is the recommended clk_m divisor value. Do not use
any other value.
This is from Section 5.1.2 "Clk_m Divisor" of the Tegra210 TRM.
> If yes I can set this change in simpler as a separate commit or
> including into existing patches.
Anything you have in mind? I tried a couple of variations to the above
and they all failed because in other places it's important that OSC is
recognized as running at 38.4 MHz. If not, then other PLLs will not
work properly and even basic things like the debug UART won't work.
Technically the right thing to do would be to base the USEC config off
the clk_m rate. We didn't do that back at the time, IIRC, because most
of the clock infrastructure didn't exist, but it might be possible to
achieve this today. I kept the above because it is still a bit simpler
and as the TRM suggests nobody should be using anything other than the
div2 setting for clk_m. I'm certainly not aware of any devices that do
something different. And U-Boot has always had this assumption as well,
so I think it's safe to use.
Thierry
> > /*
> > * Configure microsecond timers to have 1MHz clock
> > * Config register is 0xqqww, where qq is "dividend", ww is "divisor"
> > * Uses n+1 scheme
> > */
> > - switch (clock_get_osc_freq()) {
> > + switch (freq) {
> > case CLOCK_OSC_FREQ_13_0:
> > usec_config = 0x000c; /* (12+1)/(0+1) */
> > break;
> > @@ -113,6 +122,7 @@ static const struct udevice_id tegra_timer_ids[] = {
> > { .compatible = "nvidia,tegra30-timer" },
> > { .compatible = "nvidia,tegra114-timer" },
> > { .compatible = "nvidia,tegra124-timer" },
> > + { .compatible = "nvidia,tegra210-timer" },
> > { }
> > };
> > --- >8 ---
> >
> > I've also tested this on Tegra186, though no additional changes were
> > needed since Tegra186 doesn't use the Tegra timer.
> >
> > With the above folded in, the series is:
> >
> > Tested-by: Thierry Reding <treding at nvidia.com>
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