From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC PATCH] drivers: ata: Read Rx water mark value from device-tree Date: Sat, 20 Feb 2016 23:34:41 +0100 Message-ID: <28916176.WDrPajhOPa@wuerfel> References: <1455974302-7082-1-git-send-email-anuragku@xilinx.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <1455974302-7082-1-git-send-email-anuragku@xilinx.com> Sender: linux-kernel-owner@vger.kernel.org To: Anurag Kumar Vulisha Cc: robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, tj@kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, anirudh@xilinx.com, svemula@xilinx.com, punnaia@xilinx.com, Anurag Kumar Vulisha List-Id: devicetree@vger.kernel.org On Saturday 20 February 2016 18:48:22 Anurag Kumar Vulisha wrote: > index 7ca8b97..7e48dfc 100644 > --- a/Documentation/devicetree/bindings/ata/ahci-ceva.txt > +++ b/Documentation/devicetree/bindings/ata/ahci-ceva.txt > @@ -8,6 +8,7 @@ Required properties: > > Optional properties: > - ceva,broken-gen2: limit to gen1 speed instead of gen2. > + - ceva,rx-watermark: RX fifo water mark level for SATA controller. > > Examples: > ahci@fd0c0000 { > @@ -17,4 +18,5 @@ Examples: > interrupts = <0 133 4>; > clocks = <&clkc SATA_CLK_ID>; > ceva,broken-gen2; > + ceva,rx-watermark = <0x40>; > }; > How would a hardware integrator know which value is right for a particular SoC? Could it be keyed off the hardware ID? Could the bootloader perhaps set an appropriate value in the AHCI_VEND_PTC register at boot time and the driver read the initial value from it? >>From the description, it sounds like this is a policy decision rather than hardware description, and shouldn't really be in here. Arnd