From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piotr Sroka Subject: Re: [v5 2/2] dt-bindings: mtd: Add Cadence NAND controller driver Date: Fri, 13 Sep 2019 15:41:22 +0100 Message-ID: <20190913144121.GB11985@global.cadence.com> References: <20190725145804.8886-1-piotrs@cadence.com> <20190725145955.13951-1-piotrs@cadence.com> <20190830114638.33dc4eb2@xps13> <20190911150422.GA4973@global.cadence.com> <20190913144903.0323a23a@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20190913144903.0323a23a@xps13> Sender: linux-kernel-owner@vger.kernel.org To: Miquel Raynal Cc: linux-kernel@vger.kernel.org, Mark Rutland , devicetree@vger.kernel.org, Boris Brezillon , Richard Weinberger , Marek Vasut , Rob Herring , linux-mtd@lists.infradead.org, BrianNorris , David Woodhouse , Kazuhiro Kasai List-Id: devicetree@vger.kernel.org The 09/13/2019 14:49, Miquel Raynal wrote: >EXTERNAL MAIL > > >Hi Piotr, > >Piotr Sroka wrote on Wed, 11 Sep 2019 16:04:24 >+0100: > >> Hi Miquel >> >> The 08/30/2019 11:46, Miquel Raynal wrote: >> >EXTERNAL MAIL >> > >> > >> >Hi Piotr, >> > >> >Piotr Sroka wrote on Thu, 25 Jul 2019 15:59:55 >> >+0100: >> > >> >> Document the bindings used by Cadence NAND controller driver >> >> >> >> Signed-off-by: Piotr Sroka >> >> --- >> >> Changes for v5: >> >> - replace "_" by "-" in all properties >> >> - change compatible name from cdns,hpnfc to cdns,hp-nfc >> >> Changes for v4: >> >> - add commit message >> >> Changes for v3: >> >> - add unit suffix for board_delay >> >> - move child description to proper place >> >> - remove prefix cadence_ for reg and sdma fields >> >> Changes for v2: >> >> - remove chip dependends parameters from dts bindings >> >> - add names for register ranges in dts bindings >> >> - add generic bindings to describe NAND chip representation >> >> --- >> >> .../bindings/mtd/cadence-nand-controller.txt | 50 ++++++++++++++++++++++ >> >> 1 file changed, 50 insertions(+) >> >> create mode 100644 Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt >> >> >> >> diff --git a/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt b/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt >> >> new file mode 100644 >> >> index 000000000000..423547a3f993 >> >> --- /dev/null >> >> +++ b/Documentation/devicetree/bindings/mtd/cadence-nand-controller.txt >> >> @@ -0,0 +1,50 @@ >> >> +* Cadence NAND controller >> >> + >> >> +Required properties: >> >> + - compatible : "cdns,hp-nfc" >> >> + - reg : Contains two entries, each of which is a tuple consisting of a >> >> + physical address and length. The first entry is the address and >> >> + length of the controller register set. The second entry is the >> >> + address and length of the Slave DMA data port. >> >> + - reg-names: should contain "reg" and "sdma" >> >> + - interrupts : The interrupt number. >> >> + - clocks: phandle of the controller core clock (nf_clk). >> >> + >> >> +Optional properties: >> >> + - dmas: shall reference DMA channel associated to the NAND controller >> >> + - cdns,board-delay-ps : Estimated Board delay. The value includes the total >> >> + round trip delay for the signals and is used for deciding on values >> >> + associated with data read capture. The example formula for SDR mode is >> >> + the following: >> >> + board delay = RE#PAD delay + PCB trace to device + PCB trace from device >> >> + + DQ PAD delay >> >> + >> >> +Child nodes represent the available NAND chips. >> >> + >> >> +Required properties of NAND chips: >> >> + - reg: shall contain the native Chip Select ids from 0 to max supported by >> >> + the cadence nand flash controller >> >> + >> >> + >> >> +See Documentation/devicetree/bindings/mtd/nand.txt for more details on >> >> +generic bindings. >> >> + >> >> +Example: >> >> + >> >> +nand_controller: nand-controller @60000000 { >> >> + compatible = "cdns,hp-nfc"; >> >> + reg = <0x60000000 0x10000>, <0x80000000 0x10000>; >> >> + reg-names = "reg", "sdma"; >> >> + clocks = <&nf_clk>; >> >> + cdns,board-delay-ps = <4830>; >> > >> >Are you sure you want to export this to the user? Not sure it is easily >> >understandable and tunable... I'm not against but I would have troubles >> >tuning it myself, unless using the documented value. Maybe you should >> >explain more how to derive it? >> I need to export this parameter somehow. The default value may not be >> valid for other platforms. This value depends on platform, and may be different on different SoCs. So I think the DTS is the best place to put such configuration >> parameter. > >What about a different compatible if it depends on the SoC? I considered it but this dealy consists of PADs delay and PCB trace delay. PAD delays are SoC dependent. Unfortunatelly PCB delay not. What can I do I can split it on two delays, PAD_delay and trace_delay. Then handle PAD_delay by compatible and trace_delay by dts. But I am not sure whether it changes anythig. Still a delay need to passed by dts. > >This way you can retrieve a different driver data structure and avoid >the pain for the user. > >Thanks, >Miquèl Thanks Piotr