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SubjectRe: [RFC] ARM: memory: da8xx-ddrctl: new driver
On Mon, Oct 24, 2016 at 06:46:36PM +0200, Bartosz Golaszewski wrote:
> 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@baylibre.com>
> ---
> .../memory-controllers/ti-da8xx-ddrctl.txt | 20 +++
> drivers/memory/Kconfig | 8 +
> drivers/memory/Makefile | 1 +
> drivers/memory/da8xx-ddrctl.c | 187 +++++++++++++++++++++
> 4 files changed, 216 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..f0eda59
> --- /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 memory
> +maps a set of registers which allow to tweak the controller's behavior.

This is a description of the *driver*. The device itself doesn't map
some registers, it features them. Please descrive the *device*.

> +
> +Documentation:
> +OMAP-L138 (DA850) - http://www.ti.com/lit/ug/spruh82c/spruh82c.pdf
> +
> +Required properties:
> +
> +- compatible: "ti,da850-ddrctl" - for da850 SoC based boards

Perhaps:

"ti,da850-ddr-controller"

> +static int da8xx_ddrctl_probe(struct platform_device *pdev)
> +{
> + const struct da8xx_ddrctl_config_knob *knob;
> + const struct da8xx_ddrctl_setting *setting;
> + u32 regprop[2], base, memsize, reg;
> + struct device_node *node, *parent;
> + void __iomem *ddrctl;
> + const char *board;
> + struct device *dev;
> + int ret;
> +
> + dev = &pdev->dev;
> + node = dev->of_node;
> +
> + /* Find the board name. */
> + for (parent = node;
> + !of_node_is_root(parent);
> + parent = of_get_parent(parent));
> +
> + ret = of_property_read_string(parent, "compatible", &board);
> + if (ret) {
> + dev_err(dev, "unable to read the soc model\n");
> + return ret;
> + }

I can see that you want to expose sysfs knobs for this, but is it really
necessary to match boards like this? It's very fragile, and commits us
to maintaining a database of board data (i.e. a board file).

I am very much not keen on that.

> +
> + /* Check if we have settings for this board. */
> + setting = da8xx_ddrctl_match_board(board);
> + if (!setting) {
> + dev_err(dev, "no settings for board '%s'\n", board);
> + return -EINVAL;
> + }

What's wrong with of_machine_is_compatible?

> +
> + /* Figure out how to map the memory for the controller. */
> + ret = of_property_read_u32_array(node, "reg", regprop, 2);
> + if (ret) {
> + dev_err(dev, "unable to parse 'reg' property\n");
> + return ret;
> + }
> +
> + base = regprop[0];
> + memsize = regprop[1];
> +
> + ddrctl = ioremap(base, memsize);

NAK. Use the proper accessors for handling reg entries.

Thanks,
Mark.

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