Re: [PATCH v13 2/5] media: renesas: vsp1: Add support to deassert/assert reset line

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Biju,

Thank you for the patch.

On Thu, Aug 25, 2022 at 02:21:41PM +0100, Biju Das wrote:
> As the resets DT property is mandatory, and is present in all .dtsi
> in mainline, add support to perform deassert/assert using reference
> counted reset handle.
> 
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> v12->v13:
>  * Removed unused iopoll.h header file.
>  * Added Rb tag from Geert.
> v11->v12:
>  * Replaced read_poll_timeout_atomic-> udelay(1) as testing on RZ/G1N
>    shows this delay is sufficient to avoid lock-up.
>  * Removed Rb tags.
> v10->v11:
>  * To avoid lock-up on R-Car Gen2, added poll for reset status after deassert.
> v9->v10:
>  * Moved {deassert,assert} calls to vsp1_pm_runtime_{resume,suspend}
> v8->v9:
>  * No change
> v7->v8:
>  * No Change
> v6->v7:
>  * No change
> v5->v6:
>  * Rebased to media_staging and updated commit header
>  * Added Rb tag from Laurent
>  * Added forward declaration for struct reset_control
>  * Updated vsp1_device_get() with changes suggested by Laurent
>  * Updated error message for reset_control_get form ctrl->control.
> v4->v5:
>  * Added Rb tag from Geert
> v3->v4:
>  * Restored error check for pm_runtime_resume_and_get and calls
>    assert() in case of failure.
> v2->v3:
>  * Added Rb tag from Philipp
>  * If reset_control_deassert() failed, return ret directly. 
> v1->v2:
>  * Used reference counted reset handle to perform deassert/assert
> RFC->v1:
>  * Added reset support as separate patch
>  * Moved rstc just after the bus_master field in struct vsp1_device
> RFC:
>  * https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220112174612.10773-21-biju.das.jz@bp.renesas.com/
> ---
>  drivers/media/platform/renesas/vsp1/vsp1.h    |  2 ++
>  .../media/platform/renesas/vsp1/vsp1_drv.c    | 28 +++++++++++++++++--
>  2 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas/vsp1/vsp1.h b/drivers/media/platform/renesas/vsp1/vsp1.h
> index 37cf33c7e6ca..baf898d577ec 100644
> --- a/drivers/media/platform/renesas/vsp1/vsp1.h
> +++ b/drivers/media/platform/renesas/vsp1/vsp1.h
> @@ -22,6 +22,7 @@
>  struct clk;
>  struct device;
>  struct rcar_fcp_device;
> +struct reset_control;
>  
>  struct vsp1_drm;
>  struct vsp1_entity;
> @@ -79,6 +80,7 @@ struct vsp1_device {
>  	void __iomem *mmio;
>  	struct rcar_fcp_device *fcp;
>  	struct device *bus_master;
> +	struct reset_control *rstc;
>  
>  	struct vsp1_brx *brs;
>  	struct vsp1_brx *bru;
> diff --git a/drivers/media/platform/renesas/vsp1/vsp1_drv.c b/drivers/media/platform/renesas/vsp1/vsp1_drv.c
> index 1f73c48eb738..975e6851735e 100644
> --- a/drivers/media/platform/renesas/vsp1/vsp1_drv.c
> +++ b/drivers/media/platform/renesas/vsp1/vsp1_drv.c
> @@ -16,6 +16,7 @@
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
>  #include <linux/videodev2.h>
>  
>  #include <media/rcar-fcp.h>
> @@ -622,6 +623,7 @@ static int __maybe_unused vsp1_pm_runtime_suspend(struct device *dev)
>  	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
>  
>  	rcar_fcp_disable(vsp1->fcp);
> +	reset_control_assert(vsp1->rstc);
>  
>  	return 0;
>  }
> @@ -631,13 +633,30 @@ static int __maybe_unused vsp1_pm_runtime_resume(struct device *dev)
>  	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
>  	int ret;
>  
> +	ret = reset_control_deassert(vsp1->rstc);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * On R-Car Gen2, vsp1 register access after deassert can cause
> +	 * lock-up. It is a special case and needs some delay to avoid
> +	 * this lock-up.

You can reflow this to 80 columns:

	 * On R-Car Gen2, vsp1 register access after deassert can cause lock-up.
	 * It is a special case and needs some delay to avoid this lock-up.

> +	 */
> +	udelay(1);

Is it worth conditioning this on the VSP version to only add the delay
on Gen2 ?

With these two small issues addressed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +
>  	if (vsp1->info) {
>  		ret = vsp1_device_init(vsp1);
>  		if (ret < 0)
> -			return ret;
> +			goto done;
>  	}
>  
> -	return rcar_fcp_enable(vsp1->fcp);
> +	ret = rcar_fcp_enable(vsp1->fcp);
> +
> +done:
> +	if (ret < 0)
> +		reset_control_assert(vsp1->rstc);
> +
> +	return ret;
>  }
>  
>  static const struct dev_pm_ops vsp1_pm_ops = {
> @@ -825,6 +844,11 @@ static int vsp1_probe(struct platform_device *pdev)
>  	if (irq < 0)
>  		return irq;
>  
> +	vsp1->rstc = devm_reset_control_get_shared(&pdev->dev, NULL);
> +	if (IS_ERR(vsp1->rstc))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(vsp1->rstc),
> +				     "failed to get reset control\n");
> +
>  	/* FCP (optional). */
>  	fcp_node = of_parse_phandle(pdev->dev.of_node, "renesas,fcp", 0);
>  	if (fcp_node) {

-- 
Regards,

Laurent Pinchart