linux-kernel - Re: [PATCH net-next 08/10] net: mdio: Remove unnecessary (void*) conversions

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Date:   Wed, 28 Jun 2023 10:50:41 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     wuych <yunchuan@...china.com>
Cc:     iyappan@...amperecomputing.com, keyur@...amperecomputing.com,
        quan@...amperecomputing.com, andrew@...n.ch, hkallweit1@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next 08/10] net: mdio: Remove unnecessary (void*)
 conversions

Hi,

I think you missed one case:

        if (mdio_id == XGENE_MDIO_RGMII) {
                mdio_bus->read = xgene_mdio_rgmii_read;
                mdio_bus->write = xgene_mdio_rgmii_write;
                mdio_bus->priv = (void __force *)pdata;

This cast using __force is also not required.

On Wed, Jun 28, 2023 at 10:45:17AM +0800, wuych wrote:
> @@ -211,7 +211,7 @@ static void xgene_enet_wr_mdio_csr(void __iomem *base_addr,
>  static int xgene_xfi_mdio_write(struct mii_bus *bus, int phy_id,
>  				int reg, u16 data)
>  {
> -	void __iomem *addr = (void __iomem *)bus->priv;
> +	void __iomem *addr = bus->priv;
>  	int timeout = 100;
>  	u32 status, val;
>  
> @@ -234,7 +234,7 @@ static int xgene_xfi_mdio_write(struct mii_bus *bus, int phy_id,
>  
>  static int xgene_xfi_mdio_read(struct mii_bus *bus, int phy_id, int reg)
>  {
> -	void __iomem *addr = (void __iomem *)bus->priv;
> +	void __iomem *addr = bus->priv;
>  	u32 data, status, val;
>  	int timeout = 100;

These probably cause Sparse to warn whether or not the cast is there.

Given that in this case, bus->priv is initialised via:

                mdio_bus->priv = (void __force *)pdata->mdio_csr_addr;

I think the simple thing is to _always_ initialise mdio_bus->priv
to point at pdata, and have xgene_xfi_mdio_*() always do:

	struct xgene_mdio_pdata *pdata = bus->priv;
	void __iomem *addr = pdata->mdio_csr_addr;

The extra access will be dwarfed by the time taken to perform the
access.

This change should be made with a separate patch and not combined with
the patch removing the casts in xgene_mdio_rgmii_*().

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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