From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "robh+dt@kernel.org" <robh+dt@kernel.org>,
"pawel.moll@arm.com" <pawel.moll@arm.com>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"ijc+devicetree@hellion.org.uk" <ijc+devicetree@hellion.org.uk>,
"galak@codeaurora.org" <galak@codeaurora.org>,
"tj@kernel.org" <tj@kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
Anirudha Sarangi <anirudh@xilinx.com>,
Srikanth Vemula <svemula@xilinx.com>,
"Punnaiah Choudary Kalluri" <punnaia@xilinx.com>
Subject: RE: [RFC PATCH] drivers: ata: Read Rx water mark value from device-tree
Date: Mon, 22 Feb 2016 10:53:11 +0000 [thread overview]
Message-ID: <3802E9A6666DF54886E2B9CBF743BA9825E00BD4@XAP-PVEXMBX01.xlnx.xilinx.com> (raw)
In-Reply-To: <28916176.WDrPajhOPa@wuerfel>
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:
> > 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
next prev parent reply other threads:[~2016-02-22 11:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-20 13:18 [RFC PATCH] drivers: ata: Read Rx water mark value from device-tree Anurag Kumar Vulisha
2016-02-20 22:34 ` Arnd Bergmann
2016-02-22 10:53 ` Anurag Kumar Vulisha [this message]
2016-02-22 15:19 ` Arnd Bergmann
2016-02-23 5:58 ` Anurag Kumar Vulisha
2016-02-23 10:20 ` Arnd Bergmann
2016-02-23 15:29 ` Anurag Kumar Vulisha
2016-02-23 19:29 ` Rob Herring
2016-02-26 13:48 ` Anurag Kumar Vulisha
2016-03-02 5:53 ` Anurag Kumar Vulisha
2016-03-02 8:05 ` Michal Simek
2016-03-02 9:11 ` Arnd Bergmann
2016-03-02 9:27 ` Michal Simek
2016-03-02 11:42 ` Arnd Bergmann
2016-03-02 11:51 ` Michal Simek
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