Date:   Wed, 24 Jul 2019 16:09:53 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Marc Zyngier <marc.zyngier@....com>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <tglx@...utronix.de>, <jason@...edaemon.net>,
        <linus.walleij@...aro.org>, <stefan@...er.ch>,
        <mark.rutland@....com>, <pdeschrijver@...dia.com>,
        <pgaikwad@...dia.com>, <sboyd@...nel.org>,
        <linux-clk@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <jckuo@...dia.com>, <josephl@...dia.com>, <talho@...dia.com>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mperttunen@...dia.com>, <spatra@...dia.com>, <robh+dt@...nel.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH V6 01/21] irqchip: tegra: Do not disable COP IRQ during
 suspend


On 7/22/19 4:35 PM, Dmitry Osipenko wrote:
> 22.07.2019 21:38, Marc Zyngier пишет:
>> On Mon, 22 Jul 2019 09:21:21 -0700
>> Sowjanya Komatineni <skomatineni@...dia.com> wrote:
>>
>>> On 7/22/19 3:57 AM, Dmitry Osipenko wrote:
>>>> 22.07.2019 13:13, Marc Zyngier пишет:
>>>>> On 22/07/2019 10:54, Dmitry Osipenko wrote:
>>>>>> 21.07.2019 22:40, Sowjanya Komatineni пишет:
>>>>>>> Tegra210 platforms use sc7 entry firmware to program Tegra LP0/SC7 entry
>>>>>>> sequence and sc7 entry firmware is run from COP/BPMP-Lite.
>>>>>>>
>>>>>>> So, COP/BPMP-Lite still need IRQ function to finish SC7 suspend sequence
>>>>>>> for Tegra210.
>>>>>>>
>>>>>>> This patch has fix for leaving the COP IRQ enabled for Tegra210 during
>>>>>>> interrupt controller suspend operation.
>>>>>>>
>>>>>>> Acked-by: Thierry Reding <treding@...dia.com>
>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>>>>>> ---
>>>>>>>    drivers/irqchip/irq-tegra.c | 20 ++++++++++++++++++--
>>>>>>>    1 file changed, 18 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/irqchip/irq-tegra.c b/drivers/irqchip/irq-tegra.c
>>>>>>> index e1f771c72fc4..851f88cef508 100644
>>>>>>> --- a/drivers/irqchip/irq-tegra.c
>>>>>>> +++ b/drivers/irqchip/irq-tegra.c
>>>>>>> @@ -44,6 +44,7 @@ static unsigned int num_ictlrs;
>>>>>>>    
>>>>>>>    struct tegra_ictlr_soc {
>>>>>>>    	unsigned int num_ictlrs;
>>>>>>> +	bool supports_sc7;
>>>>>>>    };
>>>>>>>    
>>>>>>>    static const struct tegra_ictlr_soc tegra20_ictlr_soc = {
>>>>>>> @@ -56,6 +57,7 @@ static const struct tegra_ictlr_soc tegra30_ictlr_soc = {
>>>>>>>    
>>>>>>>    static const struct tegra_ictlr_soc tegra210_ictlr_soc = {
>>>>>>>    	.num_ictlrs = 6,
>>>>>>> +	.supports_sc7 = true,
>>>>>>>    };
>>>>>>>    
>>>>>>>    static const struct of_device_id ictlr_matches[] = {
>>>>>>> @@ -67,6 +69,7 @@ static const struct of_device_id ictlr_matches[] = {
>>>>>>>    
>>>>>>>    struct tegra_ictlr_info {
>>>>>>>    	void __iomem *base[TEGRA_MAX_NUM_ICTLRS];
>>>>>>> +	const struct tegra_ictlr_soc *soc;
>>>>>>>    #ifdef CONFIG_PM_SLEEP
>>>>>>>    	u32 cop_ier[TEGRA_MAX_NUM_ICTLRS];
>>>>>>>    	u32 cop_iep[TEGRA_MAX_NUM_ICTLRS];
>>>>>>> @@ -147,8 +150,20 @@ static int tegra_ictlr_suspend(void)
>>>>>>>    		lic->cop_ier[i] = readl_relaxed(ictlr + ICTLR_COP_IER);
>>>>>>>    		lic->cop_iep[i] = readl_relaxed(ictlr + ICTLR_COP_IEP_CLASS);
>>>>>>>    
>>>>>>> -		/* Disable COP interrupts */
>>>>>>> -		writel_relaxed(~0ul, ictlr + ICTLR_COP_IER_CLR);
>>>>>>> +		/*
>>>>>>> +		 * AVP/COP/BPMP-Lite is the Tegra boot processor.
>>>>>>> +		 *
>>>>>>> +		 * Tegra210 system suspend flow uses sc7entry firmware which
>>>>>>> +		 * is executed by COP/BPMP and it includes disabling COP IRQ,
>>>>>>> +		 * clamping CPU rail, turning off VDD_CPU, and preparing the
>>>>>>> +		 * system to go to SC7/LP0.
>>>>>>> +		 *
>>>>>>> +		 * COP/BPMP wakes up when COP IRQ is triggered and runs
>>>>>>> +		 * sc7entry-firmware. So need to keep COP interrupt enabled.
>>>>>>> +		 */
>>>>>>> +		if (!lic->soc->supports_sc7)
>>>>>>> +			/* Disable COP interrupts if SC7 is not supported */
>>>>>> All Tegra SoCs support SC7, hence the 'supports_sc7' and the comment
>>>>>> doesn't sound correct to me. Something like 'firmware_sc7' should suit
>>>>>> better here.
>>>>> If what you're saying is true, then the whole patch is wrong, and the
>>>>> SC7 property should come from DT.
>>>> It should be safe to assume that all of existing Tegra210 devices use
>>>> the firmware for SC7, hence I wouldn't say that the patch is entirely
>>>> wrong. To me it's not entirely correct.
>>> Yes, all existing Tegra210 platforms uses sc7 entry firmware for SC7 and
>>> AVP/COP IRQ need to be kept enabled as during suspend ATF triggers IRQ
>>> to COP for SC7 entry fw execution.
> Okay, as I already wrote before, it looks to me that a more proper
> solution should be to just remove everything related to COP from this
> driver instead of adding custom quirks for T210.
>
> The disabling / restoring of COP interrupts should be relevant only for
> the multimedia firmware on older Tegra SoCs. That firmware won't be ever
> supported in the upstream simply because NVIDIA abandoned the support
> for older hardware in the downstream and because it is not possible due
> to some legal weirdness (IIUC). The only variant for upstream is
> reverse-engineering of hardware (not the firmware BLOB) and writing
> proper opensource drivers for the upstream kernel, which we're already
> doing and have success to a some extent.
>
>> That's not the question. Dmitry says that the SC7 support is not a
>> property of the SoC, but mostly a platform decision on whether the
>> firmware supports SC7 or not.
>>
>> To me, that's a clear indication that this should not be hardcoded in
>> the driver, but instead obtained dynamically, via DT or otherwise.
> We already have an nvidia,suspend-mode property in the device-tree of
> the Power Management Controller node (all Tegra SoCs) which defines what
> suspending type is supported by a particular board.
>
>>>>>>> +			writel_relaxed(~0ul, ictlr + ICTLR_COP_IER_CLR);
>>>>>> Secondly, I'm also not sure why COP interrupts need to be disabled for
>>>>>> pre-T210 at all, since COP is unused. This looks to me like it was
>>>>>> cut-n-pasted from downstream kernel without a good reason and could be
>>>>>> simply removed.
>>>>> Please verify that this is actually the case. Tegra-2 definitely needed
>>>>> some level of poking, and I'm not keen on changing anything there until
>>>>> you (or someone else) has verified it on actual HW (see e307cc8941fc).
>>>> Tested on Tegra20 and Tegra30, LP1 suspend-resume works perfectly fine
>>>> with all COP bits removed from the driver.
>>>>
>>>> AFAIK, the reason why downstream needed that disabling is that it uses
>>>> proprietary firmware which is running on the COP and that firmware is
>>>> usually a BLOB audio/video DEC-ENC driver which doesn't cleanup
>>>> interrupts after itself. That firmware is not applicable for the
>>>> upstream kernel, hence there is no need to care about it.
>>>>   
>>>>> Joseph, can you please shed some light here?
>>> SC7 entry flow uses 3rd party ATF (arm-trusted FW) blob which is the
>>> one that actually loads SC7 entry firmware and triggers IRQ to
>>> AVP/COP which causes COP to wakeup and run SC7 entry FW.
>>>
>>> So when SC7 support is enabled, IRQ need to be kept enabled and when
>>> SC7 FW starts execution, it will disable COP IRQ.
>> This looks like a lot of undocumented assumptions on what firmware
>> does, as well as what firmware *is*. What I gather from this thread is
>> that there is at least two versions of firmware (a "proprietary
>> firmware" for "downstream kernels", and another one for mainline), and
>> that they do different things.
>>
>> Given that we cannot know what people actually run, I don't think we
>> can safely remove anything unless this gets tested on the full spectrum
>> of HW/FW combination.
> I'm not sure whether multiple firmware variations exist in the wild for
> Tegra210. Maybe Sowjanya or somebody else from NVIDIA could clarify. I
> think there should be some efforts in regards to a fully opensource
> firmware on Tegra210, but I'm not following it and have no idea about
> the status.
>
> You're right that there are multiple variants of suspend-resuming flow
> on Tegra SoCs. The older 32bit Tegra SoC generations have a variety of
> options in regards to suspend-resuming, including firmware-less variants
> on platforms that are having kernel running in secure mode (dev boards,
> most of Tegra20 consumer devices) and Trusted-Foundations firmware
> variant for insecure platforms (consumer devices). And yes, vendor
> firmware creates a lot of headache in regards to bringing support into
> upstream because it usually does a lot of odd undocumented things which
> may also vary depending on a firmware version (bootloader, etc) and it
> also usually difficult to replace it with an opensource alternative due
> to a crypto signing.

Tried without this patch which keeps COP IRQ disabled and I see SC7 
entry FW execution happens still.

Digging through the ATF FW code, I see on SC7 entry firmware loading 
into IRAM, COP processor is reset with RESET VECTOR set to SC7 entry 
firmware location in IRAM and on reset de-assert & unhalt COP, SC7 
firmware starts execution.

Will remove this patch in next version...

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