Re: [PATCH v7 05/15] drm/imx: dc: Flag CRTC status in GERNERALPURPOSE register

[Liu Ying <victor.liu@nxp.com>]

On Thu, Oct 29, 2026 at 11:28:37AM +0200, Laurentiu Palcu wrote:
> On Mon, Oct 26, 2026 at 06:05:10PM +0800, Liu Ying wrote:
> > Map Display Controller's register GERNERALPURPOSE at offset 0x100 and
> > create an MMIO regmap to access the register.  Create helpers
> > dc_drv_flag_crtc_{enable,disable}() with the 2 LSB bits in the register
> > to flag the CRTC enablement/disablement status.  Also, create a helper
> > dc_drv_crtc_was_enabled() so that the CRTC driver can use it to check
> > if the CRTC was enabled by a previous boot or not.  This is a preparation
> > for an upcoming patch to disable display controller at boot if the CRTC
> > was enabled by the driver during a previous boot instead of a bootloader.
> > 
> > Signed-off-by: Liu Ying <victor.liu@nxp.com>
> > --
> > v7:
> > - Newly introduced in v7 as a preparation for fixing Sashiko AI bot's
> >   comment on an upcoming patch.  (Sashiko AI bot)
> > ---
> >  drivers/gpu/drm/imx/dc/dc-drv.c | 76 +++++++++++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/imx/dc/dc-drv.h |  7 ++++
> >  2 files changed, 83 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/imx/dc/dc-drv.c b/drivers/gpu/drm/imx/dc/dc-drv.c
> > index 13795a2ad735..ac1321adf1c8 100644
> > --- a/drivers/gpu/drm/imx/dc/dc-drv.c
> > +++ b/drivers/gpu/drm/imx/dc/dc-drv.c
> > @@ -13,6 +13,7 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/pm.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/regmap.h>
> >  
> >  #include <drm/clients/drm_client_setup.h>
> >  #include <drm/drm_atomic_helper.h>
> > @@ -28,9 +29,21 @@
> >  #include "dc-drv.h"
> >  #include "dc-pe.h"
> >  
> > +/* General Purpose register offset used to flag driver usage. */
> > +#define GENERALPURPOSE		0x100
> > +#define  CRTC_ENABLED(x)	BIT(x)
> > +
> >  struct dc_priv {
> >  	struct drm_device *drm;
> >  	struct clk *clk_cfg;
> > +	struct regmap *gp_regmap;
> > +};
> > +
> > +static const struct regmap_config dc_gp_regmap_config = {
> > +	.reg_bits = 32,
> > +	.reg_stride = 4,
> > +	.val_bits = 32,
> > +	.max_register = 0,
> >  };
> >  
> >  DEFINE_DRM_GEM_DMA_FOPS(dc_drm_driver_fops);
> > @@ -156,6 +169,8 @@ static int dc_probe(struct platform_device *pdev)
> >  {
> >  	struct component_match *match = NULL;
> >  	struct dc_priv *priv;
> > +	struct resource *r;
> > +	void __iomem *base;
> >  	int ret;
> >  
> >  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> > @@ -167,6 +182,28 @@ static int dc_probe(struct platform_device *pdev)
> >  		return dev_err_probe(&pdev->dev, PTR_ERR(priv->clk_cfg),
> >  				     "failed to get cfg clock\n");
> >  
> > +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	if (!r)
> > +		return -EINVAL;
> > +
> > +	if (!devm_request_mem_region(&pdev->dev, r->start + GENERALPURPOSE, 4,
> > +				     dev_name(&pdev->dev))) {
> > +		dev_err(&pdev->dev, "failed to request memory region\n");
> > +		return -EBUSY;
> 
> Use 'return dev_err_probe()'.

Will do.  Also, will use dev_err_probe() in case platform_get_resource() fails.

> 
> > +	}
> > +
> > +	base = devm_ioremap(&pdev->dev, r->start + GENERALPURPOSE, 4);
> > +	if (!base) {
> > +		dev_err(&pdev->dev, "failed to do ioremap\n");
> > +		return -ENOMEM;
> 
> Use 'return dev_err_probe()'.

Will do.

> 
> > +	}
> > +
> > +	priv->gp_regmap = devm_regmap_init_mmio(&pdev->dev, base,
> > +						&dc_gp_regmap_config);
> > +	if (IS_ERR(priv->gp_regmap))
> > +		return dev_err_probe(&pdev->dev, PTR_ERR(priv->gp_regmap),
> > +				     "failed to init General Purpose regmap\n");
> > +
> >  	dev_set_drvdata(&pdev->dev, priv);
> >  
> >  	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > @@ -196,6 +233,45 @@ static void dc_remove(struct platform_device *pdev)
> >  	component_master_del(&pdev->dev, &dc_drm_ops);
> >  }
> >  
> > +void dc_drv_set_crtc_enable(struct dc_drm_device *dc_drm,
> > +			    unsigned int crtc_index)
> > +{
> > +	struct dc_priv *priv = dev_get_drvdata(dc_drm->base.dev);
> > +
> > +	if (WARN_ON(crtc_index > 1))
> > +		return;
> > +
> > +	regmap_set_bits(priv->gp_regmap, 0, CRTC_ENABLED(crtc_index));
> > +}
> > +
> > +void dc_drv_set_crtc_disable(struct dc_drm_device *dc_drm,
> > +			     unsigned int crtc_index)
> > +{
> > +	struct dc_priv *priv = dev_get_drvdata(dc_drm->base.dev);
> > +
> > +	if (WARN_ON(crtc_index > 1))
> > +		return;
> > +
> > +	regmap_clear_bits(priv->gp_regmap, 0, CRTC_ENABLED(crtc_index));
> > +}
> > +
> > +bool dc_drv_crtc_was_enabled(struct dc_drm_device *dc_drm,
> 
> I believe it would be better to rename this one to 'dc_drv_crtc_is_enabled'.
> After all, you're checking whether the crtc is enabled *now*. Reading those
> bits in GENERALPURPOSE show the current status, not a past one.

Will rename it.

> 
> With the above addressed:
> Reviewed-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> 
> -- 
> Thanks,
> Laurentiu

-- 
Regards,
Liu Ying