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SubjectRe: [PATCH] reset: meson: add level reset support for GX SoC family
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Hi Neil,

On Mon, 2017-10-16 at 17:26 +0200, Neil Armstrong wrote:
> The Amlogic GX SoC family embeds alternate registers to drive the reset
> levels next to the pulse registers.
>
> This patch adds support for level reset handling on the GX family only.
>
> The Meson8 family has an alternate way to handle level reset.
>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

thank you for the patch, comments below:

> ---
> drivers/reset/reset-meson.c | 57 +++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 53 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/reset/reset-meson.c b/drivers/reset/reset-meson.c
> index a8b915e..d55e440 100644
> --- a/drivers/reset/reset-meson.c
> +++ b/drivers/reset/reset-meson.c
> @@ -62,9 +62,11 @@
> #include <linux/reset-controller.h>
> #include <linux/slab.h>
> #include <linux/types.h>
> +#include <linux/of_device.h>
>
> #define REG_COUNT 8
> #define BITS_PER_REG 32
> +#define LEVEL_OFFSET 0x7c
>
> struct meson_reset {
> void __iomem *reg_base;
> @@ -88,18 +90,61 @@ static int meson_reset_reset(struct reset_controller_dev *rcdev,
> return 0;
> }
>
> -static const struct reset_control_ops meson_reset_ops = {
> +static int meson_reset_level(struct reset_controller_dev *rcdev,
> + unsigned long id, bool assert)
> +{
> + struct meson_reset *data =
> + container_of(rcdev, struct meson_reset, rcdev);
> + unsigned int bank = id / BITS_PER_REG;
> + unsigned int offset = id % BITS_PER_REG;
> + void __iomem *reg_addr = data->reg_base + LEVEL_OFFSET + (bank << 2);
> + u32 reg;
> +
> + if (bank >= REG_COUNT)
> + return -EINVAL;

This check is not necessary. The same check is in meson_reset_reset,
which I didn't notice last time.

of_reset_simple_xlate, the default rcdev->of_xlate implementation,
already guarantees id < rcdev->nr_resets. And since nr_resets is set to
REG_COUNT * BITS_PER_REG, we know that id < REG_COUNT * BITS_PER_REG and
thus bank <= id / BITS_PER_REG < REG_COUNT.

> + reg = readl(reg_addr);
> + if (assert)
> + writel(reg & ~BIT(offset), reg_addr);
> + else
> + writel(reg | BIT(offset), reg_addr);

These read-modify-write operations must be protected by a spinlock.

> +
> + return 0;
> +}
> +
> +static int meson_reset_assert(struct reset_controller_dev *rcdev,
> + unsigned long id)
> +{
> + return meson_reset_level(rcdev, id, true);
> +}
> +
> +static int meson_reset_deassert(struct reset_controller_dev *rcdev,
> + unsigned long id)
> +{
> + return meson_reset_level(rcdev, id, false);
> +}
> +
> +static const struct reset_control_ops meson_reset_meson8_ops = {
> + .reset = meson_reset_reset,
> +};
> +
> +static const struct reset_control_ops meson_reset_gx_ops = {
> .reset = meson_reset_reset,
> + .assert = meson_reset_assert,
> + .deassert = meson_reset_deassert,
> };
>
> static const struct of_device_id meson_reset_dt_ids[] = {
> - { .compatible = "amlogic,meson8b-reset", },
> - { .compatible = "amlogic,meson-gxbb-reset", },
> + { .compatible = "amlogic,meson8b-reset",
> + .data = (void *) &meson_reset_meson8_ops, },
> + { .compatible = "amlogic,meson-gxbb-reset",
> + .data = (void *) &meson_reset_gx_ops, },
> { /* sentinel */ },
> };

of_device_id.data ist const void *, so there is no need to cast here.

> static int meson_reset_probe(struct platform_device *pdev)
> {
> + const struct reset_control_ops *ops;
> struct meson_reset *data;
> struct resource *res;
>
> @@ -107,6 +152,10 @@ static int meson_reset_probe(struct platform_device *pdev)
> if (!data)
> return -ENOMEM;
>
> + ops = of_device_get_match_data(&pdev->dev);
> + if (!ops)
> + return -EINVAL;
> +
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> data->reg_base = devm_ioremap_resource(&pdev->dev, res);
> if (IS_ERR(data->reg_base))
> @@ -116,7 +165,7 @@ static int meson_reset_probe(struct platform_device *pdev)
>
> data->rcdev.owner = THIS_MODULE;
> data->rcdev.nr_resets = REG_COUNT * BITS_PER_REG;
> - data->rcdev.ops = &meson_reset_ops;
> + data->rcdev.ops = ops;
> data->rcdev.of_node = pdev->dev.of_node;
>
> return devm_reset_controller_register(&pdev->dev, &data->rcdev);

regards
Philipp

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