Hi Arnd,

-----Original Message-----
From: Arnd Bergmann [mailto:arnd@arndb.de]
Sent: Sunday, February 21, 2016 4:05 AM
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; 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:

quoted

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