From: Simon Horman <simon.horman@corigine.com>
To: Judith Mendez <jm@ti.com>
Cc: Chandrasekar Ramakrishnan <rcsekar@samsung.com>,
linux-can@vger.kernel.org,
Wolfgang Grandegger <wg@grandegger.com>,
Marc Kleine-Budde <mkl@pengutronix.de>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Schuyler Patton <spatton@ti.com>, Tero Kristo <kristo@kernel.org>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Conor Dooley <conor+dt@kernel.org>,
devicetree@vger.kernel.org,
Oliver Hartkopp <socketcan@hartkopp.net>,
Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH v7 2/2] can: m_can: Add hrtimer to generate software interrupt
Date: Thu, 25 May 2023 09:23:04 +0200 [thread overview]
Message-ID: <ZG8M2EDSG/NtiTwF@corigine.com> (raw)
In-Reply-To: <8985ea03-a7dc-a0bc-a238-3099caadf740@ti.com>
On Wed, May 24, 2023 at 04:29:01PM -0500, Judith Mendez wrote:
> Hello Simon,
>
> On 5/23/23 6:09 AM, Simon Horman wrote:
> > On Mon, May 22, 2023 at 09:37:49PM -0500, Judith Mendez wrote:
> > > Add an hrtimer to MCAN class device. Each MCAN will have its own
> > > hrtimer instantiated if there is no hardware interrupt found in
> > > device tree M_CAN node.
> > >
> > > The hrtimer will generate a software interrupt every 1 ms. In
> > > hrtimer callback, we check if there is a transaction pending by
> > > reading a register, then process by calling the isr if there is.
> > >
> > > Signed-off-by: Judith Mendez <jm@ti.com>
> >
> > ...
> >
> > > diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> > > index 94dc82644113..b639c9e645d3 100644
> > > --- a/drivers/net/can/m_can/m_can_platform.c
> > > +++ b/drivers/net/can/m_can/m_can_platform.c
> > > @@ -5,6 +5,7 @@
> > > //
> > > // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
> > > +#include <linux/hrtimer.h>
> > > #include <linux/phy/phy.h>
> > > #include <linux/platform_device.h>
> > > @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
> > > goto probe_fail;
> > > addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
> > > - irq = platform_get_irq_byname(pdev, "int0");
> > > - if (IS_ERR(addr) || irq < 0) {
> > > - ret = -EINVAL;
> > > + if (IS_ERR(addr)) {
> > > + ret = PTR_ERR(addr);
> > > goto probe_fail;
> > > }
> > > + if (device_property_present(mcan_class->dev, "interrupts") ||
> > > + device_property_present(mcan_class->dev, "interrupt-names")) {
> > > + irq = platform_get_irq_byname(pdev, "int0");
> > > + mcan_class->polling = false;
> > > + if (irq == -EPROBE_DEFER) {
> > > + ret = -EPROBE_DEFER;
> > > + goto probe_fail;
> > > + }
> > > + if (irq < 0) {
> > > + ret = -ENXIO;
> > > + goto probe_fail;
> > > + }
> > > + } else {
> > > + mcan_class->polling = true;
> > > + dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> > > + hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> > > + HRTIMER_MODE_REL_PINNED);
> > > + }
> >
> > Hi Judith,
> >
> > it seems that with this change irq is only set in the first arm of
> > the above conditional. But later on it is used unconditionally.
> > That is, it may be used uninitialised.
> >
> > Reported by gcc-12 as:
> >
> > drivers/net/can/m_can/m_can_platform.c: In function 'm_can_plat_probe':
> > drivers/net/can/m_can/m_can_platform.c:150:30: warning: 'irq' may be used uninitialized [-Wmaybe-uninitialized]
> > 150 | mcan_class->net->irq = irq;
> > | ~~~~~~~~~~~~~~~~~~~~~^~~~~
> > drivers/net/can/m_can/m_can_platform.c:86:13: note: 'irq' was declared here
> > 86 | int irq, ret = 0;
> > | ^~~
> >
>
> Maybe a good solution is to initialize irq=0 here.
If it is valid for mcan_class->net->irq to be 0 in this case,
then, yes, I agree.
> > > +
> > > /* message ram could be shared */
> > > res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
> > > if (!res) {
> > > --
> > > 2.17.1
>
>
> ~Judith
prev parent reply other threads:[~2023-05-25 7:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-23 2:37 [PATCH v7 0/2] Enable multiple MCAN on AM62x Judith Mendez
2023-05-23 2:37 ` [PATCH v7 1/2] dt-bindings: net: can: Remove interrupt properties for MCAN Judith Mendez
2023-05-23 16:58 ` Conor Dooley
2023-05-23 2:37 ` [PATCH v7 2/2] can: m_can: Add hrtimer to generate software interrupt Judith Mendez
2023-05-23 6:35 ` Marc Kleine-Budde
2023-05-24 21:20 ` Judith Mendez
2023-05-23 11:09 ` Simon Horman
2023-05-24 21:29 ` Judith Mendez
2023-05-25 7:23 ` Simon Horman [this message]
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