netdev - Re: [PATCH v3 net-next] ravb: do not write 1 to reserved bits

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Message-ID: <5bddb393-3060-6d74-4cf1-3547cb87924e@cogentembedded.com>
Date:   Tue, 18 Sep 2018 19:54:51 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Simon Horman <horms+renesas@...ge.net.au>,
        David Miller <davem@...emloft.net>
Cc:     Magnus Damm <magnus.damm@...il.com>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3 net-next] ravb: do not write 1 to reserved bits

On 09/18/2018 01:22 PM, Simon Horman wrote:

> From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> 
> EtherAVB hardware requires 0 to be written to status register bits in
> order to clear them, however, care must be taken not to:
> 
> 1. Clear other bits, by writing zero to them
> 2. Write one to reserved bits
> 
> This patch corrects the ravb driver with respect to the second point above.
> This is done by defining reserved bit masks for the affected registers and,
> after auditing the code, ensure all sites that may write a one to a
> reserved bit use are suitably masked.
> 
> Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
[...]

Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
> index 1470fc12282b..9b6bf557a2f5 100644
> --- a/drivers/net/ethernet/renesas/ravb.h
> +++ b/drivers/net/ethernet/renesas/ravb.h
> @@ -428,6 +428,7 @@ enum EIS_BIT {
>  	EIS_CULF1	= 0x00000080,
>  	EIS_TFFF	= 0x00000100,
>  	EIS_QFS		= 0x00010000,
> +	EIS_RESERVED	= (GENMASK(31, 17) | GENMASK(15, 11)),

   Well, I'm not a big fan of BIT() and GENMASK() -- they still lack a macro
to #define a bit/field value. But if you prefer to use them, OK, let's be so...

[...]

MBR, Sergei