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

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Message-ID: <12ceba49-5465-072c-1770-b57d265bee86@milecki.pl>
Date:   Thu, 2 Feb 2017 00:06:44 +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 1/2] net: ethernet: bgmac: init sequence bug

On 02/01/2017 11:39 PM, Jon Mason wrote:
> From: Zac Schroff <zschroff@...adcom.com>
>
> Fix a bug in the 'bgmac' driver init sequence that blind writes for init
> sequence where it should preserve most bits other than the ones it is
> deliberately manipulating.
>
> Signed-off-by: Zac Schroff <zschroff@...adcom.com>
> Signed-off-by: Jon Mason <jon.mason@...adcom.com>
> Fixes: f6a95a24957 ("net: ethernet: bgmac: Add platform device support")
> ---
>  drivers/net/ethernet/broadcom/bgmac-platform.c | 10 +++++++---
>  include/linux/bcma/bcma_regs.h                 |  1 +
>  2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bgmac-platform.c b/drivers/net/ethernet/broadcom/bgmac-platform.c
> index 6f736c1..9bbe05c 100644
> --- a/drivers/net/ethernet/broadcom/bgmac-platform.c
> +++ b/drivers/net/ethernet/broadcom/bgmac-platform.c
> @@ -61,15 +61,19 @@ 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 regval;
> +
> +	/* Some bits of BCMA_IOCTL set by HW/ATF & should not change */
> +	regval = bgmac_idm_read(bgmac, BCMA_IOCTL) & BCMA_IOCTL_DO_NOT_MODIFY;
> +	regval |= ((flags & (~BCMA_IOCTL_DO_NOT_MODIFY)) | BCMA_IOCTL_CLK);

You don't need these braces around whole calculation.
This should work the same:
(flags & (~BCMA_IOCTL_DO_NOT_MODIFY)) | BCMA_IOCTL_CLK


> +	bgmac_idm_write(bgmac, BCMA_IOCTL, regval | BCMA_IOCTL_FGC);
>  	bgmac_idm_read(bgmac, BCMA_IOCTL);
>
>  	bgmac_idm_write(bgmac, BCMA_RESET_CTL, 0);
>  	bgmac_idm_read(bgmac, BCMA_RESET_CTL);
>  	udelay(1);
>
> -	bgmac_idm_write(bgmac, BCMA_IOCTL, (BCMA_IOCTL_CLK | flags));
> +	bgmac_idm_write(bgmac, BCMA_IOCTL, regval);
>  	bgmac_idm_read(bgmac, BCMA_IOCTL);
>  	udelay(1);
>  }
> diff --git a/include/linux/bcma/bcma_regs.h b/include/linux/bcma/bcma_regs.h
> index 9986f82..41d7404 100644
> --- a/include/linux/bcma/bcma_regs.h
> +++ b/include/linux/bcma/bcma_regs.h
> @@ -31,6 +31,7 @@
>  #define  BCMA_IOCTL_CORE_BITS		0x3FFC
>  #define  BCMA_IOCTL_PME_EN		0x4000
>  #define  BCMA_IOCTL_BIST_EN		0x8000
> +#define  BCMA_IOCTL_DO_NOT_MODIFY	0x7FFFFF80

This sounds like a pretty bad name.

Take a look at brcmsmac and SICF_*:
http://lxr.free-electrons.com/source/drivers/net/wireless/broadcom/brcm80211/brcmsmac/d11.h?v=4.9#L1737

Or b43 and B43_BCMA_IOCTL_*:
http://lxr.free-electrons.com/source/drivers/net/wireless/broadcom/b43/b43.h?v=4.9#L494

Both drives modify bits you marked as DO_NOT_MODIFY and they are OK.