linux-kernel - Re: [PATCH RESEND 3/3] iommu: omap: Use syscon_regmap_lookup_by_phandle

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Message-ID: <e8d2b014-499c-4cbc-95b6-6ed227c4c920@arm.com>
Date: Thu, 13 Feb 2025 11:40:32 +0000
From: Robin Murphy <robin.murphy@....com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 3/3] iommu: omap: Use
 syscon_regmap_lookup_by_phandle_args

On 2025-02-12 8:19 pm, Krzysztof Kozlowski wrote:
> Use syscon_regmap_lookup_by_phandle_args() which is a wrapper over
> syscon_regmap_lookup_by_phandle() combined with getting the syscon
> argument.  Except simpler code this annotates within one line that given
> phandle has arguments, so grepping for code would be easier.
> 
> There is also no real benefit in printing errors on missing syscon
> argument, because this is done just too late: runtime check on
> static/build-time data.  Dtschema and Devicetree bindings offer the
> static/build-time check for this already.

With my suggestion for capturing a more useful general error in the 
other change, I agree with this one.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>   drivers/iommu/omap-iommu.c | 10 ++--------
>   1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
> index bce27805805010ae473aa8dbd9e0cb903dd79bba..f12812d3f828ad382c7a84f6ecd604c8f35a6d10 100644
> --- a/drivers/iommu/omap-iommu.c
> +++ b/drivers/iommu/omap-iommu.c
> @@ -1127,19 +1127,13 @@ static int omap_iommu_dra7_get_dsp_system_cfg(struct platform_device *pdev,
>   	if (!of_device_is_compatible(np, "ti,dra7-dsp-iommu"))
>   		return 0;
>   
> -	obj->syscfg =
> -		syscon_regmap_lookup_by_phandle(np, "ti,syscon-mmuconfig");
> +	obj->syscfg = syscon_regmap_lookup_by_phandle_args(np, "ti,syscon-mmuconfig",
> +							   1, &obj->id);
>   	if (IS_ERR(obj->syscfg)) {
>   		/* can fail with -EPROBE_DEFER */
>   		return PTR_ERR(obj->syscfg);
>   	}
>   
> -	if (of_property_read_u32_index(np, "ti,syscon-mmuconfig", 1,
> -				       &obj->id)) {
> -		dev_err(&pdev->dev, "couldn't get the IOMMU instance id within subsystem\n");
> -		return -EINVAL;
> -	}
> -
>   	if (obj->id != 0 && obj->id != 1) {
>   		dev_err(&pdev->dev, "invalid IOMMU instance id\n");
>   		return -EINVAL;
>