linux-kernel - Re: [PATCH 3/3] phy: marvell: phy-mvebu-a3700-comphy: Remove unsupported modes

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Date:   Fri, 27 Aug 2021 20:25:02 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Marek Behún <kabel@...nel.org>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>, Rob Herring <robh@...nel.org>,
        linux-phy@...ts.infradead.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] phy: marvell: phy-mvebu-a3700-comphy: Remove
 unsupported modes

On Friday 27 August 2021 13:27:13 Marek Behún wrote:
> On Fri, 27 Aug 2021 11:27:53 +0200
> Pali Rohár <pali@...nel.org> wrote:
> 
> > Armada 3700 does not support RXAUI, XFI and neither SFI. Remove unused
> > macros for these unsupported modes.
> > 
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > Fixes: 9695375a3f4a ("phy: add A3700 COMPHY support")
> 
> BTW I was thinking about merging some parts of these 2 drivers into
> common code. Not entirely sure if I should follow, though.

cp110-comphy and a3700-comphy are just RPC drivers which calls SMC and
relay on firmware support which implements real work. And both uses same
RPC / SMC API. So merging drivers into one is possible.

But I do not think that it is a good idea that Linux kernel depends on
some external firmware which implements RPC API for configuring HW.

Rather kernel should implements its native drivers without dependency on
external firmware.

We know from history that kernel tried to avoid using x86 BIOS/firmware
due to bugs and all functionality (re)-implemented itself without using
firmware RPC functionality.

Kernel has already "hacks" in other drivers which are using these comphy
drivers, just because older versions of firmware do not support all
necessary functionality and upgrading this firmware is not easy step
(and sometimes even not possible; e.g. when is cryptographically
signed).