Date:   Fri, 13 Oct 2023 04:16:02 -0700
From:   Emil Renner Berthing <emil.renner.berthing@...onical.com>
To:     Xingyu Wu <xingyu.wu@...rfivetech.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     aou@...s.berkeley.edu, conor@...nel.org, daniel.lezcano@...aro.org,
        devicetree@...r.kernel.org, emil.renner.berthing@...onical.com,
        krzysztof.kozlowski+dt@...aro.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, p.zabel@...gutronix.de,
        palmer@...belt.com, paul.walmsley@...ive.com, robh+dt@...nel.org,
        samin.guo@...rfivetech.com, tglx@...utronix.de,
        walker.chen@...rfivetech.com
Subject: Re: [PATCH v6 2/3] clocksource: Add JH7110 timer driver

Xingyu Wu wrote:
> On 2023/10/13 1:53, Christophe JAILLET wrote:
> > Le 12/10/2023 à 10:10, Xingyu Wu a écrit :
> >> Add timer driver for the StarFive JH7110 SoC.
> >>
> >> Signed-off-by: Xingyu Wu <xingyu.wu-bONrM45KWFOXmMXjJBpWqg@...lic.gmane.org>
> >
> > ...
>
> It looks normal in my email and the web. Is this due to some settings?
>
> >
> >> +static int jh7110_timer_probe(struct platform_device *pdev)
> >> +{
> >> +    struct jh7110_clkevt *clkevt[JH7110_TIMER_CH_MAX];
> >> +    char name[4];
> >> +    struct clk *pclk;
> >> +    struct reset_control *rst;
> >> +    int ch;
> >> +    int ret;
> >> +    void __iomem *base;
> >> +
> >> +    base = devm_platform_ioremap_resource(pdev, 0);
> >> +    if (IS_ERR(base))
> >> +        return dev_err_probe(&pdev->dev, PTR_ERR(base),
> >> +                     "failed to map registers\n");
> >> +
> >> +    rst = devm_reset_control_get_exclusive(&pdev->dev, "apb");
> >> +    if (IS_ERR(rst))
> >> +        return dev_err_probe(&pdev->dev, PTR_ERR(rst), "failed to get apb reset\n");
> >> +
> >> +    pclk = devm_clk_get_enabled(&pdev->dev, "apb");
> >> +    if (IS_ERR(pclk))
> >> +        return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
> >> +                     "failed to get & enable apb clock\n");
> >> +
> >> +    ret = reset_control_deassert(rst);
> >> +    if (ret)
> >> +        return dev_err_probe(&pdev->dev, ret, "failed to deassert apb reset\n");
> >
> > Hi,
> >
> > I'm not very familiar with the reset_control_[de]assert() functions, but shouldn't this be undone by a reset_control_assert() call if an error occurs later?
>
> In this case, the reset controller is set from 'assert' state to 'deassert' state. If it is failed and still 'assert' state, I don't think it need to call reset_control_assert().

The problem is if the assert succeeds, but the probe function fails later. Then
there is nothing to undo the deassert. A common pattern I see is something like
this:

static void jh7110_timer_reset_control_assert(void *data)
{
	reset_control_assert(data);
}

...

	ret = reset_control_deassert(rst);
	if (ret)
		return dev_err_probe(...);

	ret = devm_add_action_or_reset(&pdev->dev,
jh7110_timer_reset_control_assert, rst);
	if (ret)
		return ret;

/Emil

> >
> >> +
> >> +    for (ch = 0; ch < JH7110_TIMER_CH_MAX; ch++) {
> >> +        clkevt[ch] = devm_kzalloc(&pdev->dev, sizeof(*clkevt[ch]), GFP_KERNEL);
> >> +        if (!clkevt[ch])
> >> +            return -ENOMEM;
> >> +
> >> +        snprintf(name, sizeof(name), "ch%d", ch);
> >> +
> >> +        clkevt[ch]->base = base + JH7110_TIMER_CH_BASE(ch);
> >> +        /* Ensure timer is disabled */
> >> +        jh7110_timer_disable(clkevt[ch]);
> >> +
> >> +        rst = devm_reset_control_get_exclusive(&pdev->dev, name);
> >> +        if (IS_ERR(rst))
> >> +            return PTR_ERR(rst);
> >> +
> >> +        clkevt[ch]->clk = devm_clk_get_enabled(&pdev->dev, name);
> >> +        if (IS_ERR(clkevt[ch]->clk))
> >> +            return PTR_ERR(clkevt[ch]->clk);
> >> +
> >> +        ret = reset_control_deassert(rst);
> >> +        if (ret)
> >> +            return ret;
> >
> > Same here.
> >
> >> +
> >> +        clkevt[ch]->evt.irq = platform_get_irq(pdev, ch);
> >> +        if (clkevt[ch]->evt.irq < 0)
> >> +            return clkevt[ch]->evt.irq;
> >> +
> >> +        snprintf(clkevt[ch]->name, sizeof(clkevt[ch]->name), "%s.ch%d", pdev->name, ch);
> >> +        jh7110_clockevents_register(clkevt[ch]);
> >> +
> >> +        ret = devm_request_irq(&pdev->dev, clkevt[ch]->evt.irq, jh7110_timer_interrupt,
> >> +                       IRQF_TIMER | IRQF_IRQPOLL,
> >> +                       clkevt[ch]->name, &clkevt[ch]->evt);
> >> +        if (ret)
> >> +            return ret;
> >> +
> >> +        ret = jh7110_clocksource_init(clkevt[ch]);
> >
> > Does something should be done if this fails?
> >
> > CJ
>
> Yes, it should be call reset_control_assert() here and I will add it in next version.
>
> >
> >> +        if (ret)
> >> +            return ret;
> >> +    }
> >> +
> >> +    return 0;
> >> +}
> >> +
> >> +static const struct of_device_id jh7110_timer_match[] = {
> >> +    { .compatible = "starfive,jh7110-timer", },
> >> +    { /* sentinel */ }
> >> +};
> >> +MODULE_DEVICE_TABLE(of, jh7110_timer_match);
> >> +
> >> +static struct platform_driver jh7110_timer_driver = {
> >> +    .probe = jh7110_timer_probe,
> >> +    .driver = {
> >> +        .name = "jh7110-timer",
> >> +        .of_match_table = jh7110_timer_match,
> >> +    },
> >> +};
> >> +module_platform_driver(jh7110_timer_driver);
> >> +
> >> +MODULE_AUTHOR("Xingyu Wu <xingyu.wu-bONrM45KWFOXmMXjJBpWqg@...lic.gmane.org>");
> >> +MODULE_DESCRIPTION("StarFive JH7110 timer driver");
> >> +MODULE_LICENSE("GPL");
> >
>
> Thanks,
> Xingyu Wu
>
>
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