On Wed, Sep 04, 2024 at 01:51:35PM GMT, Alexander Stein wrote:
> From: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxx>
>
> The PIXCLK needs to be enabled in SCFG before accessing certain DCU
> registers, or the access will hang.
>
> Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxx>
> Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/fsl-dcu/Kconfig | 1 +
> drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 14 ++++++++++++++
> drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h | 3 +++
> 3 files changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/fsl-dcu/Kconfig b/drivers/gpu/drm/fsl-dcu/Kconfig
> index 5ca71ef87325..c9ee98693b48 100644
> --- a/drivers/gpu/drm/fsl-dcu/Kconfig
> +++ b/drivers/gpu/drm/fsl-dcu/Kconfig
> @@ -8,6 +8,7 @@ config DRM_FSL_DCU
> select DRM_PANEL
> select REGMAP_MMIO
> select VIDEOMODE_HELPERS
> + select MFD_SYSCON if SOC_LS1021A
> help
> Choose this option if you have an Freescale DCU chipset.
> If M is selected the module will be called fsl-dcu-drm.
> diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> index 90cbd18f096d..283858350961 100644
> --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> @@ -100,12 +100,26 @@ static void fsl_dcu_irq_uninstall(struct drm_device *dev)
> static int fsl_dcu_load(struct drm_device *dev, unsigned long flags)
> {
> struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
> + struct regmap *scfg;
> int ret;
>
> ret = fsl_dcu_drm_modeset_init(fsl_dev);
> if (ret < 0)
> return dev_err_probe(dev->dev, ret, "failed to initialize mode setting\n");
>
> + scfg = syscon_regmap_lookup_by_compatible("fsl,ls1021a-scfg");
> + if (PTR_ERR(scfg) != -ENODEV) {
> + /*
> + * For simplicity, enable the PIXCLK unconditionally. Disabling
> + * the clock in PM or on unload could be implemented as a future
> + * improvement.
This decision should be described in the commit message as well, as the
possible drawbacks (e.g. power consumption, stuck picure, etc).
> + */
> + ret = regmap_update_bits(scfg, SCFG_PIXCLKCR, SCFG_PIXCLKCR_PXCEN,
> + SCFG_PIXCLKCR_PXCEN);
> + if (ret < 0)
> + return dev_err_probe(dev->dev, ret, "failed to enable pixclk\n");
> + }
> +
> ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
> if (ret < 0) {
> dev_err(dev->dev, "failed to initialize vblank\n");
> diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
> index e2049a0e8a92..566396013c04 100644
> --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
> @@ -160,6 +160,9 @@
> #define FSL_DCU_ARGB4444 12
> #define FSL_DCU_YUV422 14
>
> +#define SCFG_PIXCLKCR 0x28
> +#define SCFG_PIXCLKCR_PXCEN BIT(31)
> +
> #define VF610_LAYER_REG_NUM 9
> #define LS1021A_LAYER_REG_NUM 10
>
> --
> 2.34.1
>
--
With best wishes
Dmitry
