[PATCH v2] drm/etnaviv: add optional reset support

[Lucas Stach]

Hi Philippe,

Am Freitag, dem 08.11.2024 um 14:00 +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
> Avoid enabling the interrupt until everything is ready
> 
> Signed-off-by: Philippe Lecointre <philippe.lecointre at thalesgroup.com>
> Reviewed-by: Simon Lenain <simon.lenain at thalesgroup.com>
> ---
> v2:
> - Add missing include of irq.h
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 30 +++++++++++++++++++++++++++
>  drivers/gpu/drm/etnaviv/etnaviv_gpu.h |  2 ++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> index 7c7f97793ddd..3e0c5dd9f74b 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * Copyright (C) 2015-2018 Etnaviv Project
> + * Copyright (C) 2024 Thales
>   */
>  
>  #include <linux/clk.h>
> @@ -8,11 +9,13 @@
>  #include <linux/delay.h>
>  #include <linux/dma-fence.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/irq.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #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"
> @@ -1629,8 +1632,24 @@ static int etnaviv_gpu_clk_enable(struct etnaviv_gpu *gpu)
>  	if (ret)
>  		goto disable_clk_core;
>  
> +	/* 32 core clock cycles (slowest clock) required before deassertion. */
> +	/* 1 microsecond might match all implementations */
> +	usleep_range(1, 2);
> +
> +	ret = reset_control_deassert(gpu->rst);
> +	if (ret)
> +		goto disable_clk_shader;
> +
> +	/* 128 core clock cycles (slowest clock) required before any activity on AHB. */
> +	/* 1 microsecond might match all implementations */
> +	usleep_range(1, 2);

Mashing the reset handling into the clock handling is a bad idea. The
clocks are en-/disabled during runtime PM handling. The etnaviv driver
is written in a way that the GPU does not necessarily need to be reset
during a runtime PM transition, which allow for faster startup times.

The reset handling should really be its own separate function and would
logically go into etnaviv_gpu_init() between the pm_runtime_get_sync()
and etnaviv_hw_identify().

> +
> +	enable_irq(gpu->irq);

Do you see any issues with the IRQ being enabled earlier? A GPU being
held in reset should not be able to trigger a IRQ.

> +
>  	return 0;
>  
> +disable_clk_shader:
> +	clk_disable_unprepare(gpu->clk_shader);
>  disable_clk_core:
>  	clk_disable_unprepare(gpu->clk_core);
>  disable_clk_bus:
> @@ -1643,6 +1662,8 @@ static int etnaviv_gpu_clk_enable(struct etnaviv_gpu *gpu)
>  
>  static int etnaviv_gpu_clk_disable(struct etnaviv_gpu *gpu)
>  {
> +	disable_irq(gpu->irq);
> +	reset_control_assert(gpu->rst);
>  	clk_disable_unprepare(gpu->clk_shader);
>  	clk_disable_unprepare(gpu->clk_core);
>  	clk_disable_unprepare(gpu->clk_bus);
> @@ -1876,6 +1897,9 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
>  	if (gpu->irq < 0)
>  		return gpu->irq;
>  
> +	/* Avoid enabling the interrupt until everything is ready */
> +	irq_set_status_flags(gpu->irq, IRQ_NOAUTOEN);
> +
>  	err = devm_request_irq(&pdev->dev, gpu->irq, irq_handler, 0,
>  			       dev_name(gpu->dev), gpu);
>  	if (err) {
> @@ -1883,6 +1907,12 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> +	/* Get Reset: */
> +	gpu->rst = devm_reset_control_get_optional(&pdev->dev, NULL);
> +	if (IS_ERR(gpu->rst))
> +		return dev_err_probe(dev, PTR_ERR(gpu->rst),
> +				     "failed to get reset\n");
> +
>  	/* Get Clocks: */
>  	gpu->clk_reg = devm_clk_get_optional(&pdev->dev, "reg");
>  	DBG("clk_reg: %p", gpu->clk_reg);
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> index 31322195b9e4..8c181191755e 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> @@ -1,6 +1,7 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>  /*
>   * Copyright (C) 2015-2018 Etnaviv Project
> + * Copyright (C) 2024 Thales

I don't think adding a single member here does warrant a Copyright
statement, in fact I would prefer them to not be touched at all.
Authorship of individual changes to the driver a clearly attributable
via the git history.

Regards,
Lucas
>   */
>  
>  #ifndef __ETNAVIV_GPU_H__
> @@ -157,6 +158,7 @@ struct etnaviv_gpu {
>  	struct clk *clk_reg;
>  	struct clk *clk_core;
>  	struct clk *clk_shader;
> +	struct reset_control *rst;
>  
>  	unsigned int freq_scale;
>  	unsigned int fe_waitcycles;