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(2a01cb058192e70090a4fe44d3d1f079.ipv6.abo.wanadoo.fr. [2a01:cb05:8192:e700:90a4:fe44:d3d1:f079]) by smtp.gmail.com with ESMTPSA id u6sm11308532wrp.83.2021.08.11.01.36.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Aug 2021 01:36:58 -0700 (PDT) Subject: Re: [PATCH net-next 1/2] net: pcs: xpcs: enable skip xPCS soft reset To: Wong Vee Khee , Andrew Lunn Cc: Vivien Didelot , "David S . Miller" , Jakub Kicinski , Giuseppe Cavallaro , Alexandre Torgue , Jose Abreu , Maxime Coquelin , Heiner Kallweit , Russell King , Voon Weifeng , Michael Sit Wei Hong , Vladimir Oltean , linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210809102229.933748-1-vee.khee.wong@linux.intel.com> <20210809102229.933748-2-vee.khee.wong@linux.intel.com> <20210810235529.GB30818@linux.intel.com> From: Florian Fainelli Message-ID: Date: Wed, 11 Aug 2021 01:36:56 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210810235529.GB30818@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/10/2021 4:55 PM, Wong Vee Khee wrote: > Hi Andrew, > On Mon, Aug 09, 2021 at 03:35:09PM +0200, Andrew Lunn wrote: >> On Mon, Aug 09, 2021 at 06:22:28PM +0800, Wong Vee Khee wrote: >>> From: Michael Sit Wei Hong >>> >>> Unlike any other platforms, Intel AlderLake-S uses Synopsys SerDes where >>> all the SerDes PLL configurations are controlled by the xPCS at the BIOS >>> level. If the driver perform a xPCS soft reset on initialization, these >>> settings will be switched back to the power on reset values. >>> >>> This changes the xpcs_create function to take in an additional argument >>> to check if the platform request to skip xPCS soft reset during device >>> initialization. >> >> Why not just call into the BIOS and ask it to configure the SERDES? >> Isn't that what ACPI is all about, hiding the details from the OS? Or >> did the BIOS writers not add a control method to do this? >> >> Andrew > > BIOS does configured the SerDes. The problem here is that all the > configurations done by BIOS are being reset at xpcs_create(). > > We would want user of the pcs-xpcs module (stmmac, sja1105) to have > control whether or not we need to perform to the soft reset in the > xpcs_create() call. I understood Andrew's response as suggesting to introduce the ability for xpcs_create() to make a BIOS call which would configure the SerDes after xpcs_soft_reset(). That way the current xpcs_create() signature would remain the same, but you could easily hook any post-reset initialization by making an appropriate BIOS call. -- Florian