linux-kernel - Re: [PATCH v2 1/2] net: ethernet: bgmac: init sequence bug

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Date:   Fri, 3 Feb 2017 22:41:48 +0100
From:   Rafał Miłecki <rafal@...ecki.pl>
To:     Jon Mason <jon.mason@...adcom.com>,
        David Miller <davem@...emloft.net>
Cc:     bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zac Schroff <zschroff@...adcom.com>
Subject: Re: [PATCH v2 1/2] net: ethernet: bgmac: init sequence bug

On 02/03/2017 10:08 PM, Jon Mason wrote:
> @@ -61,15 +60,20 @@ static bool platform_bgmac_clk_enabled(struct bgmac *bgmac)
>
>  static void platform_bgmac_clk_enable(struct bgmac *bgmac, u32 flags)
>  {
> -	bgmac_idm_write(bgmac, BCMA_IOCTL,
> -			(BCMA_IOCTL_CLK | BCMA_IOCTL_FGC | flags));
> +	u32 val;
> +
> +	val = bgmac_idm_read(bgmac, BCMA_IOCTL);
> +	/* Some bits of BCMA_IOCTL set by HW/ATF and should not change */
> +	val |= flags & ~(BGMAC_AWCACHE | BGMAC_ARCACHE | BGMAC_AWUSER |
> +			 BGMAC_ARUSER);
> +	val |= BGMAC_CLK_EN;
>  	bgmac_idm_read(bgmac, BCMA_IOCTL);

This read was previously following write op most likely to flush it or
something. I don't think it makes any sense to read after read.