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Message-ID: <20181105091922.gws52ledkqwc46xx@M43218.corp.atmel.com>
Date: Mon, 5 Nov 2018 10:19:22 +0100
From: Ludovic Desroches <ludovic.desroches@...rochip.com>
To: Jean-Michel Hautbois <jhautbois@...il.com>
CC: <boris.brezillon@...tlin.com>,
Nicolas Ferre <nicolas.ferre@...el.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: sama5d: using the ebi interface from another driver
Hi Jean-Michel,
On Fri, Nov 02, 2018 at 02:35:26PM +0100, Jean-Michel Hautbois wrote:
> Hi all,
>
> I have a custom board based on a sama5d3 chip. The SoC is connected to
> 2 pef24628 SHDSL transceivers, the first one on ebi@...00000 and the
> second one on ebi@...00000.
> I tried to write a basic char driver, using request_mem_region and
> ioremap but I can't read or write into the device.
> I have to say that the driver is based on a proprietary one, and
> tested years ago on a PowerPC board.
>
> Then, after looking into deeper details in the datasheet I understand
> it is connected through EBI and it sounds not so easy :D.
>
> I would appreciate some help/pointers on this, as there is (at least,
> I could find) few documentation on how to use it except for NAND
> cases.
>
> I have something like that in my DTS, but not sure this is the correct
> way to do it :
>
> ebi: ebi@...00000 {
> pinctrl-0 = <&pinctrl_ebi_nand_addr>;
> pinctrl-names = "default";
> status = "okay";
>
> dsp0: pef24628@1 {
> status = "okay";
> compatible = "intel,pef24628";
> #address-cells = <1>;
> #size-cells = <1>;
> reg = <0x1 0x0 0x8000>;
> pinctrl-0 = <&pinctrl_dsp_cs1>;
> };
>
> dsp1: pef24628@2 {
> status = "okay";
> compatible = "intel,pef24628";
> #address-cells = <1>;
> #size-cells = <1>;
> reg = <0x2 0x0 0x8000>;
> pinctrl-0 = <&pinctrl_dsp_cs2>;
> };
>
> nand_controller: nand-controller {
> status = "okay";
>
> nand@3 {
> reg = <0x3 0x0 0x2>;
> atmel,rb = <0>;
> nand-bus-width = <8>;
> nand-ecc-mode = "hw";
> nand-ecc-strength = <4>;
> nand-ecc-step-size = <512>;
> nand-on-flash-bbt;
> label = "atmel_nand";
>
> partitions {
> compatible = "fixed-partitions";
> #address-cells = <1>;
> #size-cells = <1>;
> [...]
> };
> };
> };
>
> The pinctrl for ebi should probably be changed however, I am wondering
> how the (platform ?) driver can access the adress ? Should it parse
> itself the parent, and find range, etc. Or is there an accessor for it
> ?
At first look, your DT seems correct. You have nothing special to do,
the usual platform_get_resource() and devm_ioremap_resource() calls are enough.
The address translation should be done automatically according to ranges
property.
Another hint is to check and specify the signals timings.
Regards
Ludovic
>
> Maybe can I just manually toggle the CS GPIO, and don't try to make
> anything more complex than what it should be ? The driver should not
> be atmel dependant...
>
> Thanks !
> JM
>
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