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Subject: Re: [PATCH v3 4/7] drm/panfrost: Add support for multiple regulators
To:     Nicolas Boichat <drinkcat@chromium.org>,
        Rob Herring <robh+dt@kernel.org>
Cc:     Mark Rutland <mark.rutland@arm.com>, devicetree@vger.kernel.org,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        David Airlie <airlied@linux.ie>, linux-kernel@vger.kernel.org,
        Liam Girdwood <lgirdwood@gmail.com>,
        dri-devel@lists.freedesktop.org, Mark Brown <broonie@kernel.org>,
        linux-mediatek@lists.infradead.org,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        hsinyi@chromium.org, Matthias Brugger <matthias.bgg@gmail.com>,
        linux-arm-kernel@lists.infradead.org
References: <20200114071602.47627-1-drinkcat@chromium.org>
 <20200114071602.47627-5-drinkcat@chromium.org>
From:   Steven Price <steven.price@arm.com>
Message-ID: <7e82cac2-efbf-806b-8c2e-04dbd0482b50@arm.com>
Date:   Mon, 20 Jan 2020 14:43:10 +0000
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On 14/01/2020 07:15, Nicolas Boichat wrote:
> Some GPUs, namely, the bifrost/g72 part on MT8183, have a second
> regulator for their SRAM, let's add support for that.
> 
> We extend the framework in a generic manner so that we could
> support more than 2 regulators, if required.
> 
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> 
> ---
> 
> v3:
>  - Make this more generic, by allowing any number of regulators
>    (in practice we fix the maximum number of regulators to 2, but
>    this could be increased easily).
>  - We only probe the second regulator if the device tree matching
>    data asks for it.
>  - I couldn't find a way to detect the number of regulators in the
>    device tree, if we wanted to refuse to probe the device if there
>    are too many regulators, which might be required for safety, see
>    the thread on v2 [1].
>  - The discussion also included the idea of a separate device tree
>    entry for a "soft PDC", or at least a separate driver. I'm not
>    sure to understand the full picture, and how different vendors
>    implement this, so I'm still integrating everything in the main
>    driver. I'd be happy to try to make mt8183 fit into such a
>    framework after it's created, but I don't think I'm best placed
>    to implement (and again, the main purpose of this was to test
>    if the binding is correct).

From discussions offline, I think I've come round to the view that
having a "soft PDC" in device tree isn't the right solution. Device tree
should be describing the hardware and that isn't actually a hardware
component.

I guess we'll have to wait to see how many devices have a similar
'quirk' and whether it's worth representing this is software in a more
generic manner, or if matching on compatible strings will be sufficient
for the devices that need multiple regulators.

One (minor) comment below, but otherwise LGTM.

> 
> [1] https://patchwork.kernel.org/patch/11322839/
> 
>  drivers/gpu/drm/panfrost/panfrost_device.c | 25 ++++++++++++-------
>  drivers/gpu/drm/panfrost/panfrost_device.h | 15 +++++++++++-
>  drivers/gpu/drm/panfrost/panfrost_drv.c    | 28 +++++++++++++++-------
>  3 files changed, 50 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index 238fb6d54df4732..c30e0a3772a4f57 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -87,18 +87,26 @@ static void panfrost_clk_fini(struct panfrost_device *pfdev)
>  
>  static int panfrost_regulator_init(struct panfrost_device *pfdev)
>  {
> -	int ret;
> +	int ret, i;
>  
> -	pfdev->regulator = devm_regulator_get(pfdev->dev, "mali");
> -	if (IS_ERR(pfdev->regulator)) {
> -		ret = PTR_ERR(pfdev->regulator);
> -		dev_err(pfdev->dev, "failed to get regulator: %d\n", ret);
> +	BUG_ON(pfdev->comp->num_supplies > ARRAY_SIZE(pfdev->regulators));
> +
> +	for (i = 0; i < pfdev->comp->num_supplies; i++) {
> +		pfdev->regulators[i].supply = pfdev->comp->supply_names[i];
> +	}
> +
> +	ret = devm_regulator_bulk_get(pfdev->dev,
> +				      pfdev->comp->num_supplies,
> +				      pfdev->regulators);
> +	if (ret < 0) {
> +		dev_err(pfdev->dev, "failed to get regulators: %d\n", ret);
>  		return ret;
>  	}
>  
> -	ret = regulator_enable(pfdev->regulator);
> +	ret = regulator_bulk_enable(pfdev->comp->num_supplies,
> +				    pfdev->regulators);
>  	if (ret < 0) {
> -		dev_err(pfdev->dev, "failed to enable regulator: %d\n", ret);
> +		dev_err(pfdev->dev, "failed to enable regulators: %d\n", ret);
>  		return ret;
>  	}
>  
> @@ -107,7 +115,8 @@ static int panfrost_regulator_init(struct panfrost_device *pfdev)
>  
>  static void panfrost_regulator_fini(struct panfrost_device *pfdev)
>  {
> -	regulator_disable(pfdev->regulator);
> +	regulator_bulk_disable(pfdev->comp->num_supplies,
> +			pfdev->regulators);
>  }
>  
>  int panfrost_device_init(struct panfrost_device *pfdev)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 06713811b92cdf7..021f063ffb3747f 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -7,6 +7,7 @@
>  
>  #include <linux/atomic.h>
>  #include <linux/io-pgtable.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/spinlock.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_mm.h>
> @@ -19,6 +20,7 @@ struct panfrost_job;
>  struct panfrost_perfcnt;
>  
>  #define NUM_JOB_SLOTS 3
> +#define MAX_REGULATORS 2
>  
>  struct panfrost_features {
>  	u16 id;
> @@ -51,6 +53,16 @@ struct panfrost_features {
>  	unsigned long hw_issues[64 / BITS_PER_LONG];
>  };
>  
> +/*
> + * Features that cannot be automatically detected and need matching using the
> + * compatible string, typically SoC-specific.
> + */
> +struct panfrost_compatible {
> +	/* Supplies count and names. */
> +	int num_supplies;
> +	const char * const *supply_names;
> +};
> +
>  struct panfrost_device {
>  	struct device *dev;
>  	struct drm_device *ddev;
> @@ -59,10 +71,11 @@ struct panfrost_device {
>  	void __iomem *iomem;
>  	struct clk *clock;
>  	struct clk *bus_clock;
> -	struct regulator *regulator;
> +	struct regulator_bulk_data regulators[MAX_REGULATORS];
>  	struct reset_control *rstc;
>  
>  	struct panfrost_features features;
> +	const struct panfrost_compatible* comp;
>  
>  	spinlock_t as_lock;
>  	unsigned long as_in_use_mask;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 48e3c4165247cea..db3563b80150c9d 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -510,6 +510,10 @@ static int panfrost_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, pfdev);
>  
> +	pfdev->comp = of_device_get_match_data(&pdev->dev);
> +	if (!pfdev->comp)
> +		return -ENODEV;
> +
>  	/* Allocate and initialze the DRM device. */
>  	ddev = drm_dev_alloc(&panfrost_drm_driver, &pdev->dev);
>  	if (IS_ERR(ddev))
> @@ -581,16 +585,22 @@ static int panfrost_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +const char * const default_supplies[] = { "mali" };

This should be static.

Steve

> +static const struct panfrost_compatible default_data = {
> +	.num_supplies = ARRAY_SIZE(default_supplies),
> +	.supply_names = default_supplies,
> +};
> +
>  static const struct of_device_id dt_match[] = {
> -	{ .compatible = "arm,mali-t604" },
> -	{ .compatible = "arm,mali-t624" },
> -	{ .compatible = "arm,mali-t628" },
> -	{ .compatible = "arm,mali-t720" },
> -	{ .compatible = "arm,mali-t760" },
> -	{ .compatible = "arm,mali-t820" },
> -	{ .compatible = "arm,mali-t830" },
> -	{ .compatible = "arm,mali-t860" },
> -	{ .compatible = "arm,mali-t880" },
> +	{ .compatible = "arm,mali-t604", .data = &default_data, },
> +	{ .compatible = "arm,mali-t624", .data = &default_data, },
> +	{ .compatible = "arm,mali-t628", .data = &default_data, },
> +	{ .compatible = "arm,mali-t720", .data = &default_data, },
> +	{ .compatible = "arm,mali-t760", .data = &default_data, },
> +	{ .compatible = "arm,mali-t820", .data = &default_data, },
> +	{ .compatible = "arm,mali-t830", .data = &default_data, },
> +	{ .compatible = "arm,mali-t860", .data = &default_data, },
> +	{ .compatible = "arm,mali-t880", .data = &default_data, },
>  	{}
>  };
>  MODULE_DEVICE_TABLE(of, dt_match);
>