linux-kernel - Re: [PATCH] clocksource/drivers/sp804: avoid error on multiple instances

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Date:   Wed, 27 Apr 2022 16:42:12 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Andre Przywara <andre.przywara@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Zhen Lei <thunder.leizhen@...wei.com>
Subject: Re: [PATCH] clocksource/drivers/sp804: avoid error on multiple
 instances

On 2022-04-27 15:27, Andre Przywara wrote:
> When a machine sports more than one SP804 timer instance, we only bring
> up the first one, since multiple timers of the same kind are not useful
> to Linux. As this is intentional behaviour, we should not return an
> error message, as we do today:
> ===============
> [    0.000800] Failed to initialize '/bus@...0000/motherboard-bus@...0000/iofpga-bus@...000000/timer@...000': -22
> ===============
> 
> Replace the -EINVAL return with an informative message and return 0
> instead.
> 
> Also we do not reach the init function anymore if the DT node is
> disabled (as this is now handled by OF_DECLARE), so remove the explicit
> check for that case.
> 
> This fixes a long standing bogus error when booting ARM's fastmodels.

And on Juno too, hooray! :)

> Signed-off-by: Andre Przywara <andre.przywara@....com>
> ---
>   drivers/clocksource/timer-sp804.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/clocksource/timer-sp804.c b/drivers/clocksource/timer-sp804.c
> index 401d592e85f5a..30cbc580e0448 100644
> --- a/drivers/clocksource/timer-sp804.c
> +++ b/drivers/clocksource/timer-sp804.c
> @@ -259,6 +259,12 @@ static int __init sp804_of_init(struct device_node *np, struct sp804_timer *time
>   	struct clk *clk1, *clk2;
>   	const char *name = of_get_property(np, "compatible", NULL);
>   
> +	if (initialized) {
> +		pr_info("%s: only instantiating one timer\n",
> +			of_node_full_name(np));

Nit: %pOF? However, do we really need to print anything at all? As it 
is, the message already looks ambiguously like it might be saying that 
this node *is* the one timer that we're instantiating, however we'll 
have already logged the registration of an SP804 clocksource, so further 
messages about what we *aren't* doing seem little more useful than 
pr_info("not waxing an owl") IMO.

Cheers,
Robin.

> +		return 0;
> +	}
> +
>   	base = of_iomap(np, 0);
>   	if (!base)
>   		return -ENXIO;
> @@ -270,11 +276,6 @@ static int __init sp804_of_init(struct device_node *np, struct sp804_timer *time
>   	writel(0, timer1_base + timer->ctrl);
>   	writel(0, timer2_base + timer->ctrl);
>   
> -	if (initialized || !of_device_is_available(np)) {
> -		ret = -EINVAL;
> -		goto err;
> -	}
> -
>   	clk1 = of_clk_get(np, 0);
>   	if (IS_ERR(clk1))
>   		clk1 = NULL;