Hi Arnd, > -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Sunday, February 21, 2016 4:05 AM > To: Anurag Kumar Vulisha > Cc: robh+dt@xxxxxxxxxx; pawel.moll@xxxxxxx; mark.rutland@xxxxxxx; > ijc+devicetree@xxxxxxxxxxxxxx; galak@xxxxxxxxxxxxxx; tj@xxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux- > ide@xxxxxxxxxxxxxxx; Anirudha Sarangi; Srikanth Vemula; Punnaiah Choudary > Kalluri; Anurag Kumar Vulisha > Subject: Re: [RFC PATCH] drivers: ata: Read Rx water mark value from device- > tree > > 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. > Thanks for reviewing the patch. Can I use module_param() for this watermark instead of reading it from devicetree or doing it in bootloader. In bootloader we are initializing serdes controller for high speed devices. As a part of this initialization we will be reseting all the high speed pheripherals which are using serdes, so SATA will also get resetted. Because of this reason, can I use module_param() for Rxwatermark value instead? Thanks, Anurag Kumar V > Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
