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SubjectRe: [PATCH v7 2/2] can: m_can: Add hrtimer to generate software interrupt
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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.

>> +
>> /* message ram could be shared */
>> res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>> if (!res) {
>> --
>> 2.17.1


~Judith

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