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

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

Hi Biju,

On Sat, Aug 27, 2022 at 04:07:56PM +0000, Biju Das wrote:
> > Subject: Re: [PATCH v13 2/5] media: renesas: vsp1: Add support to deassert/assert reset line
> > 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:
> > >  *
> > > ---
> > >  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.
> > 
> > > +	 */
> 
> OK, but after adding conditional check for Gen2, it will look like [1]
> 
> > > +	udelay(1);
> > 
> > Is it worth conditioning this on the VSP version to only add the delay
> > on Gen2 ?
> 
> Will fix this in next version like [1], if it is Ok to everyone.

Works for me.

> > With these two small issues addressed,
> 
> [1]
>         if (vsp1->info) {                                                        
>  70 +               /*                                                               
>  71 +                * On R-Car Gen2 and RZ/G1, vsp1 register access after deassert  
>  72 +                * can cause lock-up.                                            
>  73 +                * It is a special case and needs some delay to avoid this       
>  74 +                * lock-up.                                                      


As a general rule, flow the text with sentence following each others
without line breaks, all the way to 80 columns. You can break a comment
in paragraphs, and there should then be a blank line between paragraphs.
You can thus write

		 * On R-Car Gen2 and RZ/G1, vsp1 register access after deassert  
		 * can cause lock-up.                                            
		 *
		 * It is a special case and needs some delay to avoid this       
		 * lock-up.                                                      

or

		 * On R-Car Gen2 and RZ/G1, vsp1 register access after deassert
		 * can cause lock-up. It is a special case and needs some delay
		 * to avoid this lock-up.

but not

		 * On R-Car Gen2 and RZ/G1, vsp1 register access after deassert
		 * can cause lock-up.
		 * It is a special case and needs some delay to avoid this
		 * lock-up.

(I think the second option is better here)

>  75 +                */                                                              
>  76 +               if (vsp1->info->gen == 2)                                        
>  77 +                       udelay(1);
> 
> > 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);
-- 
Regards,

Laurent Pinchart