linux-kernel - Re: [PATCH v2 07/11] bus: rifsc: introduce RIFSC firewall controller driver

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Message-ID: <ZMD027pTNT/HCLe6@corigine.com>
Date:   Wed, 26 Jul 2023 12:26:35 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     Gatien Chevallier <gatien.chevallier@...s.st.com>
Cc:     Oleksii_Moisieiev@...m.com, gregkh@...uxfoundation.org,
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Subject: Re: [PATCH v2 07/11] bus: rifsc: introduce RIFSC firewall controller
 driver

On Tue, Jul 25, 2023 at 06:41:00PM +0200, Gatien Chevallier wrote:

...

> diff --git a/drivers/bus/stm32_rifsc.c b/drivers/bus/stm32_rifsc.c

...

> +static int stm32_rif_acquire_semaphore(struct stm32_firewall_controller *stm32_firewall_controller,
> +				       int id)
> +{
> +	void __iomem *addr = stm32_firewall_controller->mmio + RIFSC_RISC_PER0_SEMCR + 0x8 * id;
> +
> +	__set_bit(SEMCR_MUTEX, addr);

Hi Gatien,

Sparse seem a bit unhappy about this.

 .../stm32_rifsc.c:83:9: warning: cast removes address space '__iomem' of expression
 .../stm32_rifsc.c:83:9: warning: incorrect type in argument 2 (different address spaces)
 .../stm32_rifsc.c:83:9:    expected unsigned long volatile *addr
 .../stm32_rifsc.c:83:9:    got void [noderef] __iomem *addr
 .../stm32_rifsc.c:83:9: warning: incorrect type in argument 2 (different address spaces)
 .../stm32_rifsc.c:83:9:    expected unsigned long volatile *addr
 .../stm32_rifsc.c:83:9:    got void [noderef] __iomem *addr

But it's not immediately apparent to me what a good solution is.

> +
> +	/* Check that CID1 has the semaphore */
> +	if (stm32_rifsc_is_semaphore_available(addr) ||
> +	    FIELD_GET(RIFSC_RISC_SCID_MASK, readl(addr)) != RIF_CID1)
> +		return -EACCES;
> +
> +	return 0;
> +}

...