On Fri, May 30, 2025 at 12:23:50AM GMT, Michal Wilczynski wrote:
> Update the Imagination PVR DRM driver to leverage the pwrseq framework
> for managing the power sequence of the GPU on the T-HEAD TH1520 SoC.
>
> In pvr_device_init(), the driver now attempts to get a handle to the
> "gpu-power" sequencer target using devm_pwrseq_get(). If successful,
> the responsibility for powering on and off the GPU's core clocks and
> resets is delegated to the power sequencer. Consequently, the GPU
> driver conditionally skips acquiring the GPU reset line if the pwrseq
> handle is obtained, as the sequencer's match function will acquire it.
> Clock handles are still acquired by the GPU driver for other purposes
> like devfreq.
>
> The runtime PM callbacks, pvr_power_device_resume() and
> pvr_power_device_suspend(), are modified to call pwrseq_power_on() and
> pwrseq_power_off() respectively when the sequencer is present. If no
> sequencer is found, the driver falls back to its existing manual clock
> and reset management. A helper function,
> pvr_power_off_sequence_manual(), is introduced to encapsulate the manual
> power-down logic.
>
> Signed-off-by: Michal Wilczynski <m.wilczyn...@samsung.com>
> ---
> drivers/gpu/drm/imagination/Kconfig | 1 +
> drivers/gpu/drm/imagination/pvr_device.c | 33 +++++++++++--
> drivers/gpu/drm/imagination/pvr_device.h | 6 +++
> drivers/gpu/drm/imagination/pvr_power.c | 82
> +++++++++++++++++++++-----------
> 4 files changed, 89 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/imagination/Kconfig
> b/drivers/gpu/drm/imagination/Kconfig
> index
> 3bfa2ac212dccb73c53bdc2bc259bcba636e7cfc..737ace77c4f1247c687cc1fde2f139fc2e118c50
> 100644
> --- a/drivers/gpu/drm/imagination/Kconfig
> +++ b/drivers/gpu/drm/imagination/Kconfig
> @@ -11,6 +11,7 @@ config DRM_POWERVR
> select DRM_SCHED
> select DRM_GPUVM
> select FW_LOADER
> + select POWER_SEQUENCING
Messed indent.
> help
> Choose this option if you have a system that has an Imagination
> Technologies PowerVR (Series 6 or later) or IMG GPU.
> diff --git a/drivers/gpu/drm/imagination/pvr_device.c
> b/drivers/gpu/drm/imagination/pvr_device.c
> index
> 8b9ba4983c4cb5bc40342fcafc4259078bc70547..19d48bbc828cf2b8dbead602e90ff88780152124
> 100644
> --- a/drivers/gpu/drm/imagination/pvr_device.c
> +++ b/drivers/gpu/drm/imagination/pvr_device.c
> @@ -25,6 +25,7 @@
> #include <linux/interrupt.h>
> #include <linux/platform_device.h>
> #include <linux/pm_runtime.h>
> +#include <linux/pwrseq/consumer.h>
> #include <linux/reset.h>
> #include <linux/slab.h>
> #include <linux/stddef.h>
> @@ -631,10 +632,34 @@ pvr_device_init(struct pvr_device *pvr_dev)
> if (err)
> return err;
>
> - /* Get the reset line for the GPU */
> - err = pvr_device_reset_init(pvr_dev);
> - if (err)
> - return err;
> + /*
> + * Try to get a power sequencer. If successful, it will handle clocks
> + * and resets. Otherwise, we fall back to managing them ourselves.
> + */
> + pvr_dev->pwrseq = devm_pwrseq_get(dev, "gpu-power");
> + if (IS_ERR(pvr_dev->pwrseq)) {
> + int pwrseq_err = PTR_ERR(pvr_dev->pwrseq);
> +
> + /*
> + * If the error is -EPROBE_DEFER, it's because the
> + * optional sequencer provider is not present
> + * and it's safe to fall back on manual power-up.
It is safe but why it is desirable? The rule is rather to defer the
probe, assuming this is probe path.
Best regards,
Krzysztof
