linux-kernel - Re: [PATCH] drm/panfrost: Dynamically allocate pm

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Message-ID: <f408da05-a825-c392-6484-3a665cc0dbd6@arm.com>
Date:   Tue, 15 Feb 2022 12:09:16 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        Steven Price <steven.price@....com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH] drm/panfrost: Dynamically allocate pm_domains

On 2022-02-14 20:31, Alyssa Rosenzweig wrote:
> MT8192 requires 5 power domains. Rather than bump MAX_PM_DOMAINS and
> waste memory on every supported Panfrost chip, instead dynamically
> allocate pm_domain_devs and pm_domain_links. This adds some flexibility;
> it seems inevitable a new MediaTek device will require more than 5
> domains.
> 
> On non-MediaTek devices, this saves a small amount of memory.
> 
> Suggested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>
> ---
>   drivers/gpu/drm/panfrost/panfrost_device.c | 14 ++++++++++----
>   drivers/gpu/drm/panfrost/panfrost_device.h |  5 ++---
>   2 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index ee612303f076..661cdec320af 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -127,7 +127,10 @@ static void panfrost_pm_domain_fini(struct panfrost_device *pfdev)
>   {
>   	int i;
>   
> -	for (i = 0; i < ARRAY_SIZE(pfdev->pm_domain_devs); i++) {
> +	if (!pfdev->pm_domain_devs || !pfdev->pm_domain_links)
> +		return;
> +
> +	for (i = 0; i < pfdev->comp->num_pm_domains; i++) {
>   		if (!pfdev->pm_domain_devs[i])
>   			break;
>   
> @@ -161,9 +164,12 @@ static int panfrost_pm_domain_init(struct panfrost_device *pfdev)
>   		return -EINVAL;
>   	}
>   
> -	if (WARN(num_domains > ARRAY_SIZE(pfdev->pm_domain_devs),
> -			"Too many supplies in compatible structure.\n"))
> -		return -EINVAL;
> +	pfdev->pm_domain_devs = devm_kcalloc(pfdev->dev, num_domains,
> +					     sizeof(*pfdev->pm_domain_devs),
> +					     GFP_KERNEL);
> +	pfdev->pm_domain_links = devm_kcalloc(pfdev->dev, num_domains,
> +					      sizeof(*pfdev->pm_domain_links),
> +					      GFP_KERNEL);

Since we're not really doing any detailed management of our device 
links, could we get away with using AUTOREMOVE_CONSUMER instead of 
STATELESS to avoid having to explicitly keep track of them ourselves?

Robin.

>   
>   	for (i = 0; i < num_domains; i++) {
>   		pfdev->pm_domain_devs[i] =
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 8b25278f34c8..98e3039696f9 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -22,7 +22,6 @@ struct panfrost_job;
>   struct panfrost_perfcnt;
>   
>   #define NUM_JOB_SLOTS 3
> -#define MAX_PM_DOMAINS 3
>   
>   struct panfrost_features {
>   	u16 id;
> @@ -87,8 +86,8 @@ struct panfrost_device {
>   	struct regulator_bulk_data *regulators;
>   	struct reset_control *rstc;
>   	/* pm_domains for devices with more than one. */
> -	struct device *pm_domain_devs[MAX_PM_DOMAINS];
> -	struct device_link *pm_domain_links[MAX_PM_DOMAINS];
> +	struct device **pm_domain_devs;
> +	struct device_link **pm_domain_links;
>   	bool coherent;
>   
>   	struct panfrost_features features;