linux-kernel - Re: [PATCH v3] drm/etnaviv: add optional reset support

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Message-ID: <3fa8279a44649ed9a893e88f1a9c562349a9d393.camel@pengutronix.de>
Date: Mon, 09 Dec 2024 11:06:41 +0100
From: Lucas Stach <l.stach@...gutronix.de>
To: LECOINTRE Philippe <philippe.lecointre@...lesgroup.com>, Russell King
 <linux+etnaviv@...linux.org.uk>, Christian Gmeiner
 <christian.gmeiner@...il.com>
Cc: David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 "etnaviv@...ts.freedesktop.org" <etnaviv@...ts.freedesktop.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, LENAIN Simon
 <simon.lenain@...lesgroup.com>,  BARBEAU Etienne
 <etienne.barbeau@...lesgroup.com>, LEJEUNE Sebastien
 <sebastien.lejeune@...lesgroup.com>
Subject: Re: [PATCH v3] drm/etnaviv: add optional reset support

Hi Philippe,

Am Freitag, dem 06.12.2024 um 17:00 +0000 schrieb LECOINTRE Philippe:
> Add optional reset support which is mentioned in vivante,gc.yaml to
> allow the driver to work on SoCs whose reset signal is asserted by default
> 
> Signed-off-by: Philippe Lecointre <philippe.lecointre@...lesgroup.com>
> Reviewed-by: Simon Lenain <simon.lenain@...lesgroup.com>

Upstream usually doesn't put much weight on such internal reviews. No
harm here, as the patch is simple enough and I do review it before
applying. Just as a hint for the future: if you want maintainers to
take such reviews into account for speeding up the adoption of a patch,
do the review on the public mailing lists.

> ---
> v3:
> - Rework to match initial feedback
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 37 +++++++++++++++++++++++++++
>  drivers/gpu/drm/etnaviv/etnaviv_gpu.h |  1 +
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> index 2d4c112ce033..1961ebac315a 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> @@ -13,6 +13,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/reset.h>
>  #include <linux/thermal.h>
>  
>  #include "etnaviv_cmdbuf.h"
> @@ -172,6 +173,25 @@ int etnaviv_gpu_get_param(struct etnaviv_gpu *gpu, u32 param, u64 *value)
>  	return 0;
>  }
>  
> +static int etnaviv_gpu_reset_deassert(struct etnaviv_gpu *gpu)
> +{
> +	int ret;
> +
> +	/* 32 core clock cycles (slowest clock) required before deassertion */
> +	/* 1 microsecond might match all implementations without computation */

I missed to mention this before, as I was focused on the technical
side: this is not the multiline comment style used in the
kernel/etnaviv. Please use the same style as already found in this
file.

> +	usleep_range(1, 2);
> +
> +	ret = reset_control_deassert(gpu->rst);
> +	if (ret)
> +		return ret;
> +
> +	/* 128 core clock cycles (slowest clock) required before any activity on AHB */
> +	/* 1 microsecond might match all implementations without computation */
> +	usleep_range(1, 2);
> +
> +	return 0;
> +}
> +
>  static inline bool etnaviv_is_model_rev(struct etnaviv_gpu *gpu, u32 model, u32 revision)
>  {
>  	return gpu->identity.model == model &&
> @@ -799,6 +819,12 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
>  		goto pm_put;
>  	}
>  
> +	ret = etnaviv_gpu_reset_deassert(gpu);
> +	if (ret) {
> +		dev_err(gpu->dev, "GPU reset deassert failed\n");
> +		goto fail;
> +	}
> +
>  	etnaviv_hw_identify(gpu);
>  
>  	if (gpu->identity.model == 0) {
> @@ -1860,6 +1886,17 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
>  	if (IS_ERR(gpu->mmio))
>  		return PTR_ERR(gpu->mmio);
>  
> +
> +	/* Get Reset: */
> +	gpu->rst = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
> +	if (IS_ERR(gpu->rst))
> +		return dev_err_probe(dev, PTR_ERR(gpu->rst),
> +				     "failed to get reset\n");
> +
> +	err = reset_control_assert(gpu->rst);
> +	if (err)
> +		return dev_err_probe(dev, err, "failed to assert reset\n");
> +
>  	/* Get Interrupt: */
>  	gpu->irq = platform_get_irq(pdev, 0);
>  	if (gpu->irq < 0)
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> index 4d8a7d48ade3..0985ea548b82 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> @@ -158,6 +158,7 @@ struct etnaviv_gpu {
>  	struct clk *clk_reg;
>  	struct clk *clk_core;
>  	struct clk *clk_shader;
> +	struct reset_control *rst;

This needs a forward declaration of struct reset_control in the header,
to avoid build failures if headers are included in a different order.
Please put them right next to the existing ones for regulator and clk.

Other than that, patch looks good to me.

Regards,
Lucas

>  
>  	unsigned int freq_scale;
>  	unsigned int fe_waitcycles;