Hi Matthias,
On 2020-08-20 12:58, Matthias Schiffer wrote:
> The PIXCLK needs to be enabled in SCFG before accessing the DCU on LS1021A,
> or the access will hang.
Hm, this seems a rather ad-hoc access to SCFG from the DCU. We do
support a pixel clock in the device tree bindings of fsl-dcu, so ideally
we should enable the pixel clock through the clock framework.
On the other hand, I guess that would mean adding a clock driver to flip
a single bit, which seems a bit excessive too.
I'd like a second opinion on that. Adding clk framework maintainers.
--
Stefan
>
> Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/fsl-dcu/Kconfig | 1 +
> drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 25 +++++++++++++++++++++++
> drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h | 3 +++
> 3 files changed, 29 insertions(+)
>
> diff --git a/drivers/gpu/drm/fsl-dcu/Kconfig b/drivers/gpu/drm/fsl-dcu/Kconfig
> index d7dd8ba90e3a..9e5a35e7c00c 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 abbc1ddbf27f..8a7556655581 100644
> --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> @@ -51,6 +51,23 @@ static const struct regmap_config fsl_dcu_regmap_config = {
> .volatile_reg = fsl_dcu_drm_is_volatile_reg,
> };
>
> +static int fsl_dcu_scfg_config_ls1021a(struct device_node *np)
> +{
> + struct regmap *scfg;
> +
> + scfg = syscon_regmap_lookup_by_compatible("fsl,ls1021a-scfg");
> + if (IS_ERR(scfg))
> + return PTR_ERR(scfg);
> +
> + /*
> + * For simplicity, enable the PIXCLK unconditionally. It might
> + * be possible to disable the clock in PM or on unload as a future
> + * improvement.
> + */
> + return regmap_update_bits(scfg, SCFG_PIXCLKCR, SCFG_PIXCLKCR_PXCEN,
> + SCFG_PIXCLKCR_PXCEN);
> +}
> +
> static void fsl_dcu_irq_uninstall(struct drm_device *dev)
> {
> struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
> @@ -70,6 +87,14 @@ static int fsl_dcu_load(struct drm_device *dev,
> unsigned long flags)
> return ret;
> }
>
> + if (of_device_is_compatible(fsl_dev->np, "fsl,ls1021a-dcu")) {
> + ret = fsl_dcu_scfg_config_ls1021a(fsl_dev->np);
> + if (ret < 0) {
> + dev_err(dev->dev, "failed to enable pixclk\n");
> + goto done;
> + }
> + }
> +
> 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
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