- trimmed cc-list
On Thu, 17 Dec 2020 at 19:08, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> Add OPP and SoC core voltage scaling support to the display controller
> driver. This is required for enabling system-wide DVFS on pre-Tegra186
> SoCs.
>
> Tested-by: Peter Geis <pgwipeout@xxxxxxxxx>
> Tested-by: Nicolas Chauvet <kwizart@xxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> ---
> drivers/gpu/drm/tegra/dc.c | 66 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
> index b6676f1fe358..105ad786e432 100644
> --- a/drivers/gpu/drm/tegra/dc.c
> +++ b/drivers/gpu/drm/tegra/dc.c
> @@ -11,9 +11,12 @@
> #include <linux/interconnect.h>
> #include <linux/module.h>
> #include <linux/of_device.h>
> +#include <linux/pm_domain.h>
> +#include <linux/pm_opp.h>
> #include <linux/pm_runtime.h>
> #include <linux/reset.h>
>
> +#include <soc/tegra/common.h>
> #include <soc/tegra/pmc.h>
>
> #include <drm/drm_atomic.h>
> @@ -1699,6 +1702,48 @@ int tegra_dc_state_setup_clock(struct tegra_dc *dc,
> return 0;
> }
>
> +static void tegra_dc_update_voltage_state(struct tegra_dc *dc,
> + struct tegra_dc_state *state)
> +{
> + unsigned long rate, pstate;
> + struct dev_pm_opp *opp;
> + int err;
> +
> + /* calculate actual pixel clock rate which depends on internal divider */
> + rate = DIV_ROUND_UP(clk_get_rate(dc->clk) * 2, state->div + 2);
> +
> + /* find suitable OPP for the rate */
> + opp = dev_pm_opp_find_freq_ceil(dc->dev, &rate);
> +
> + if (opp == ERR_PTR(-ERANGE))
> + opp = dev_pm_opp_find_freq_floor(dc->dev, &rate);
> +
> + /* -ENOENT means that this device-tree doesn't have OPP table */
> + if (opp == ERR_PTR(-ENOENT))
> + return;
> +
> + if (IS_ERR(opp)) {
> + dev_err(dc->dev, "failed to find OPP for %luHz: %pe\n",
> + rate, opp);
> + return;
> + }
> +
> + pstate = dev_pm_opp_get_voltage(opp);
> + dev_pm_opp_put(opp);
> +
> + /*
> + * The minimum core voltage depends on the pixel clock rate (which
> + * depends on internal clock divider of the CRTC) and not on the
> + * rate of the display controller clock. This is why we're not using
> + * dev_pm_opp_set_rate() API and instead controlling the power domain
> + * directly.
> + */
> + err = dev_pm_genpd_set_performance_state(dc->dev, pstate);
As you state above, in general we should not need to call the
dev_pm_genpd_set_performance_state() directly for the consumer driver.
Even if this looks like a special case to me, I would appreciate a
confirmation from Viresh that this is the way he also would like to
move forward from the opp library perspective.
> + if (err)
> + dev_err(dc->dev, "failed to set power domain state to %lu: %d\n",
> + pstate, err);
> +}
> +
[...]
Kind regards
Uffe
