From: Thierry Reding <thierry.reding@gmail.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Venkat Reddy Talla <vreddytalla@nvidia.com>,
linux-kernel@vger.kernel.org,
Jonathan Hunter <jonathanh@nvidia.com>,
Sowjanya Komatineni <skomatineni@nvidia.com>,
linux-tegra@vger.kernel.org, Dmitry Osipenko <digetx@gmail.com>,
kernel-team@android.com, Thomas Gleixner <tglx@linutronix.de>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/3] soc/tegra: pmc: Don't create fake interrupt hierarchy levels
Date: Mon, 5 Oct 2020 13:33:35 +0200 [thread overview]
Message-ID: <20201005113335.GT425362@ulmo> (raw)
In-Reply-To: <20201005111443.1390096-4-maz@kernel.org>
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On Mon, Oct 05, 2020 at 12:14:43PM +0100, Marc Zyngier wrote:
> The Tegra PMC driver does ungodly things with the interrupt hierarchy,
> repeatedly corrupting it by pulling hwirq numbers out of thin air,
> overriding existing IRQ mappings and changing the handling flow
> of unsuspecting users.
>
> All of this is done in the name of preserving the interrupt hierarchy
> even when these levels do not exist in the HW. Together with the use
> of proper IRQs for IPIs, this leads to an unbootable system as the
> rescheduling IPI gets repeatedly repurposed for random drivers...
>
> Instead, let's allow the hierarchy to be trimmed to the level that
> actually makes sense for the HW, and not any deeper. This avoids
> having unnecessary callbacks, overriding mappings, and otherwise
> keeps the hierarchy sane.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> drivers/soc/tegra/pmc.c | 79 +++++++++++++++--------------------------
> 1 file changed, 29 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
> index 9960f7c18431..4eea3134fb3e 100644
> --- a/drivers/soc/tegra/pmc.c
> +++ b/drivers/soc/tegra/pmc.c
> @@ -1993,6 +1993,30 @@ static int tegra_pmc_irq_translate(struct irq_domain *domain,
> return 0;
> }
>
> +/* Trim the irq hierarchy from a particular irq domain */
> +static void trim_hierarchy(unsigned int virq, struct irq_domain *domain)
> +{
> + struct irq_data *tail, *irq_data = irq_get_irq_data(virq);
> +
> + /* The PMC doesn't generate any interrupt by itself */
> + if (WARN_ON(!irq_data->parent_data))
> + return;
> +
> + /* Skip until we find the right domain */
> + while (irq_data->parent_data && irq_data->parent_data->domain != domain)
> + irq_data = irq_data->parent_data;
> +
> + /* Sever the inner part of the hierarchy... */
> + tail = irq_data->parent_data;
> + irq_data->parent_data = NULL;
> +
> + /* ... and free it */
> + for (irq_data = tail; irq_data; irq_data = tail) {
> + tail = irq_data->parent_data;
> + kfree(irq_data);
> + };
> +}
That kind of looks like what I originally wanted to do and (naively)
thought that passing the (0, NULL, NULL) triplet would achieve.
Given that this is fairly low-level stuff that deals with the inner
workings of the IRQ infrastructure, should we eventually pull this out
of the driver and make it into a core helper? I don't seriously expect
this to be widely useful, but putting it into the core might help keep
it more maintainable.
I volunteer to do that work if you think it's a good idea.
Thierry
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next prev parent reply other threads:[~2020-10-05 11:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 11:14 [PATCH 0/3] soc/tegra: Prevent the PMC driver from corrupting interrupt routing Marc Zyngier
2020-10-05 11:14 ` [PATCH 1/3] gpio: tegra186: Allow optional irq parent callbacks Marc Zyngier
2020-10-05 11:14 ` [PATCH 2/3] soc/tegra: pmc: " Marc Zyngier
2020-10-05 11:27 ` Thierry Reding
2020-10-05 12:59 ` Marc Zyngier
2020-10-05 11:14 ` [PATCH 3/3] soc/tegra: pmc: Don't create fake interrupt hierarchy levels Marc Zyngier
2020-10-05 11:33 ` Thierry Reding [this message]
2020-10-05 13:10 ` Marc Zyngier
2020-10-05 11:22 ` [PATCH 0/3] soc/tegra: Prevent the PMC driver from corrupting interrupt routing Thierry Reding
2020-10-05 13:06 ` Marc Zyngier
2020-10-05 15:45 ` Thierry Reding
2020-10-05 18:23 ` Jon Hunter
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