netdev - Re: [PATCH V2 1/3] net: ks8851-ml: Remove 8-bit bus accessors

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Message-Id: <20200216.194130.1790846276699458141.davem@davemloft.net>
Date:   Sun, 16 Feb 2020 19:41:30 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     marex@...x.de
Cc:     netdev@...r.kernel.org, lukas@...ner.de, ynezz@...e.cz,
        yuehaibing@...wei.com
Subject: Re: [PATCH V2 1/3] net: ks8851-ml: Remove 8-bit bus accessors

From: Marek Vasut <marex@...x.de>
Date: Sat, 15 Feb 2020 17:54:17 +0100

> This driver is mixing 8-bit and 16-bit bus accessors for reasons unknown,
> however the speculation is that this was some sort of attempt to support
> the 8-bit bus mode.
> 
> As per the KS8851-16MLL documentation, all two registers accessed via the
> 8-bit accessors are internally 16-bit registers, so reading them using
> 16-bit accessors is fine. The KS_CCR read can be converted to 16-bit read
> outright, as it is already a concatenation of two 8-bit reads of that
> register. The KS_RXQCR accesses are 8-bit only, however writing the top
> 8 bits of the register is OK as well, since the driver caches the entire
> 16-bit register value anyway.
> 
> Finally, the driver is not used by any hardware in the kernel right now.
> The only hardware available to me is one with 16-bit bus, so I have no
> way to test the 8-bit bus mode, however it is unlikely this ever really
> worked anyway. If the 8-bit bus mode is ever required, it can be easily
> added by adjusting the 16-bit accessors to do 2 consecutive accesses,
> which is how this should have been done from the beginning.
> 
> Signed-off-by: Marek Vasut <marex@...x.de>

Applied.