linux-kernel - Re: [RFC v2] ARM: memory: da8xx-ddrctl: new driver

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Date:   Tue, 25 Oct 2016 13:23:46 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Sekhar Nori <nsekhar@...com>, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Russell King <linux@...linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Jyri Sarha <jsarha@...com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [RFC v2] ARM: memory: da8xx-ddrctl: new driver

Kevin Hilman <khilman@...libre.com> writes:

> Bartosz Golaszewski <bgolaszewski@...libre.com> writes:
>
>> Create a new driver for the da8xx DDR2/mDDR controller and implement
>> support for writing to the Peripheral Bus Burst Priority Register.
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>> ---
>>  .../memory-controllers/ti-da8xx-ddrctl.txt         |  20 +++
>>  drivers/memory/Kconfig                             |   8 +
>>  drivers/memory/Makefile                            |   1 +
>>  drivers/memory/da8xx-ddrctl.c                      | 175 +++++++++++++++++++++
>>  4 files changed, 204 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
>>  create mode 100644 drivers/memory/da8xx-ddrctl.c
>>
>> diff --git
>> a/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
>> b/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
>> new file mode 100644
>> index 0000000..7e271dd
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
>> @@ -0,0 +1,20 @@
>> +* Device tree bindings for Texas Instruments da8xx DDR2/mDDR memory controller
>> +
>> +The DDR2/mDDR memory controller present on Texas Instruments da8xx SoCs features
>> +a set of registers which allow to tweak the controller's behavior.
>> +
>> +Documentation:
>> +OMAP-L138 (DA850) - http://www.ti.com/lit/ug/spruh82c/spruh82c.pdf
>> +
>> +Required properties:
>> +
>> +- compatible:		"ti,da850-ddr-controller" - for da850 SoC based boards
>> +- reg:			a tuple containing the base address of the memory
>> +			controller and the size of the memory area to map
>> +
>> +Example for da850 shown below.
>> +
>> +ddrctl {
>> +	compatible = "ti,da850-ddr-controller";
>> +	reg = <0xB0000000 0x100>;
>> +};
>
> Axel's series for the USB PHY reminded me that the PHY also has some
> config registers in this same area, and his series creates a syscon for
> a similar range of registers.
>
> Could you create a syscon for the SYSCFG0 registers, which would then
> be used by ths driver and your other drivers/bus driver?  Then the
> binding  would just reference the sysconf via phandle, and your driver
> can use syscon_regmap_lookup_by_phandle()

Nevermind. I though that the config register in this driver was also in
SYSCFG0, but I see now that it's in the reg region of the DDR controller
itself, so no syscon is needed.

Kevin