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bh=SzEpVJRZUWtd025zQUfcikjEtXWKzq+av2jgcHORPGQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XIlPzMZ0o40/8IGoqQJDRj4MNdbA2EcrweEVJWe/qpPwIymlfFS79vWcVrugzaPKz ugUCUBNeeoM9948c4ZCcGaoEB96/gblqrUchIrHqoyilanOZIQrJUy6SBkfglMC5MH BqE5JI2iG/eJTehbrxYAmgP9d+6crEBfNtHsSWek= Date: Fri, 26 Jun 2026 10:29:54 +0100 From: Liviu Dudau To: Boris Brezillon Cc: Steven Price , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Nicolas Frattaroli , Chia-I Wu , Karunika Choo , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, sashiko-bot@kernel.org Subject: Re: [PATCH 05/11] drm/panthor: Fix theoretical IOMEM access in suspended state Message-ID: References: <20260625-panthor-misc-fixes-v1-0-b67ed973fea6@collabora.com> <20260625-panthor-misc-fixes-v1-5-b67ed973fea6@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260625-panthor-misc-fixes-v1-5-b67ed973fea6@collabora.com> On Thu, Jun 25, 2026 at 02:40:31PM +0200, Boris Brezillon wrote: > In theory, our hardirq handler can be called while the device (and > thus the panthor_irq) is suspended, because the IRQ line is shared. > In practice though, in all the designs we've seen, the line is only > shared within the GPU, and because sub-component suspend state is > consistent (all-suspended or all-resumed), we shouldn't end up with > an interrupt triggered while we're suspended. > > Fix the problem anyway, if nothing else, for our sanity. > > Fixes: 0b2d86670a84 ("drm/panthor: Rework panthor_irq::suspended into panthor_irq::state") > Reported-by: sashiko-bot@kernel.org > Closes: https://sashiko.dev/#/patchset/20260625-panthor-signal-from-irq-v4-0-3d2908912afa@collabora.com?part=1 > Signed-off-by: Boris Brezillon > --- > drivers/gpu/drm/panthor/panthor_device.h | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h > index 35679bfa1f3a..a39386bd6382 100644 > --- a/drivers/gpu/drm/panthor/panthor_device.h > +++ b/drivers/gpu/drm/panthor/panthor_device.h > @@ -512,9 +512,6 @@ static irqreturn_t panthor_ ## __name ## _irq_raw_handler(int irq, void *data) > struct panthor_irq *pirq = data; \ > enum panthor_irq_state old_state; \ > \ > - if (!gpu_read(pirq->iomem, INT_STAT)) \ > - return IRQ_NONE; \ > - \ > guard(spinlock_irqsave)(&pirq->mask_lock); \ > old_state = atomic_cmpxchg(&pirq->state, \ > PANTHOR_IRQ_STATE_ACTIVE, \ > @@ -522,6 +519,13 @@ static irqreturn_t panthor_ ## __name ## _irq_raw_handler(int irq, void *data) > if (old_state != PANTHOR_IRQ_STATE_ACTIVE) \ > return IRQ_NONE; \ > \ > + if (!gpu_read(pirq->iomem, INT_STAT)) { \ > + atomic_cmpxchg(&pirq->state, \ > + PANTHOR_IRQ_STATE_PROCESSING, \ > + PANTHOR_IRQ_STATE_ACTIVE); \ > + return IRQ_NONE; \ > + } \ Hmm, I get it that you're trying to revert the effect of the previous atomic_cmpxchg() here but it feels like a better option would be to not do the swap at all if the state is not ACTIVE. Best regards, Liviu > + \ > gpu_write(pirq->iomem, INT_MASK, 0); \ > return IRQ_WAKE_THREAD; \ > } \ > > -- > 2.54.0 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯