On Tue, Sep 12, 2023 at 4:22 PM Janne Grunau via B4 Relay <devnull+j.jannau.net@xxxxxxxxxx> wrote: > > From: Janne Grunau <j@xxxxxxxxxx> > > Multiple power domains need to be handled explicitly in each driver. The > driver core can not handle it automatically since it is not aware of > power sequencing requirements the hardware might have. This is not a > problem for simpledrm since everything is expected to be powered on by > the bootloader. simpledrm has just ensure it remains powered on during > its lifetime. > This is required on Apple silicon M2 and M2 Pro/Max/Ultra desktop > systems. The HDMI output initialized by the bootloader requires keeping > the display controller and a DP phy power domain on. > > Signed-off-by: Janne Grunau <j@xxxxxxxxxx> > --- > Changes in v2: > - removed broken drm_err() log statement only ment for debugging > - removed commented cast > - use correct format spcifier for 'int' in log statement > - add 'continue;' after failure to get device for power_domain > - use drm_warn() in non fatal error cases > - removed duplicate PTR_ERR conversion > - Link to v1: https://lore.kernel.org/r/20230910-simpledrm-multiple-power-domains-v1-1-f8718aefc685@xxxxxxxxxx > --- > drivers/gpu/drm/tiny/simpledrm.c | 105 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 105 insertions(+) > > diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c > index ff86ba1ae1b8..9c597461d1e2 100644 > --- a/drivers/gpu/drm/tiny/simpledrm.c > +++ b/drivers/gpu/drm/tiny/simpledrm.c > @@ -6,6 +6,7 @@ > #include <linux/of_address.h> > #include <linux/platform_data/simplefb.h> > #include <linux/platform_device.h> > +#include <linux/pm_domain.h> > #include <linux/regulator/consumer.h> > > #include <drm/drm_aperture.h> > @@ -227,6 +228,12 @@ struct simpledrm_device { > unsigned int regulator_count; > struct regulator **regulators; > #endif > + /* power-domains */ > +#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS > + int pwr_dom_count; > + struct device **pwr_dom_devs; > + struct device_link **pwr_dom_links; > +#endif > > /* simplefb settings */ > struct drm_display_mode mode; > @@ -468,6 +475,101 @@ static int simpledrm_device_init_regulators(struct simpledrm_device *sdev) > } > #endif > > +#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS > +/* > + * Generic power domain handling code. > + * > + * Here we handle the power-domains properties of our "simple-framebuffer" > + * dt node. This is only necessary if there is more than one power-domain. > + * A single power-domains is handled automatically by the driver core. Multiple > + * power-domains have to be handled by drivers since the driver core can't know > + * the correct power sequencing. Power sequencing is not an issue for simpledrm > + * since the bootloader has put the power domains already in the correct state. > + * simpledrm has only to ensure they remain active for its lifetime. > + * > + * When the driver unloads, we detach from the power-domains. > + * > + * We only complain about errors here, no action is taken as the most likely > + * error can only happen due to a mismatch between the bootloader which set > + * up the "simple-framebuffer" dt node, and the PM domain providers in the > + * device tree. Chances are that there are no adverse effects, and if there are, > + * a clean teardown of the fb probe will not help us much either. So just > + * complain and carry on, and hope that the user actually gets a working fb at > + * the end of things. > + */ > +static void simpledrm_device_detach_genpd(void *res) > +{ > + int i; > + struct simpledrm_device *sdev = res; > + > + if (sdev->pwr_dom_count <= 1) > + return; > + > + for (i = sdev->pwr_dom_count - 1; i >= 0; i--) { > + if (!sdev->pwr_dom_links[i]) > + device_link_del(sdev->pwr_dom_links[i]); > + if (!IS_ERR_OR_NULL(sdev->pwr_dom_devs[i])) > + dev_pm_domain_detach(sdev->pwr_dom_devs[i], true); > + } > +} > + > +static int simpledrm_device_attach_genpd(struct simpledrm_device *sdev) > +{ > + struct device *dev = sdev->dev.dev; > + int i; > + > + sdev->pwr_dom_count = of_count_phandle_with_args(dev->of_node, "power-domains", > + "#power-domain-cells"); > + /* > + * Single power-domain devices are handled by driver core nothing to do > + * here. The same for device nodes without "power-domains" property. > + */ > + if (sdev->pwr_dom_count <= 1) > + return 0; > + > + sdev->pwr_dom_devs = devm_kcalloc(dev, sdev->pwr_dom_count, > + sizeof(*sdev->pwr_dom_devs), > + GFP_KERNEL); > + if (!sdev->pwr_dom_devs) > + return -ENOMEM; > + > + sdev->pwr_dom_links = devm_kcalloc(dev, sdev->pwr_dom_count, > + sizeof(*sdev->pwr_dom_links), > + GFP_KERNEL); > + if (!sdev->pwr_dom_links) > + return -ENOMEM; > + > + for (i = 0; i < sdev->pwr_dom_count; i++) { > + sdev->pwr_dom_devs[i] = dev_pm_domain_attach_by_id(dev, i); > + if (IS_ERR(sdev->pwr_dom_devs[i])) { > + int ret = PTR_ERR(sdev->pwr_dom_devs[i]); > + if (ret == -EPROBE_DEFER) { > + simpledrm_device_detach_genpd(sdev); > + return ret; > + } > + drm_warn(&sdev->dev, > + "pm_domain_attach_by_id(%u) failed: %d\n", i, ret); > + continue; > + } > + > + sdev->pwr_dom_links[i] = device_link_add(dev, > + sdev->pwr_dom_devs[i], > + DL_FLAG_STATELESS | > + DL_FLAG_PM_RUNTIME | > + DL_FLAG_RPM_ACTIVE); > + if (!sdev->pwr_dom_links[i]) > + drm_warn(&sdev->dev, "failed to link power-domain %d\n", i); > + } > + > + return devm_add_action_or_reset(dev, simpledrm_device_detach_genpd, sdev); > +} > +#else > +static int simpledrm_device_attach_genpd(struct simpledrm_device *sdev) > +{ > + return 0; > +} > +#endif > + > /* > * Modesetting > */ > @@ -651,6 +753,9 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv, > if (ret) > return ERR_PTR(ret); > ret = simpledrm_device_init_regulators(sdev); > + if (ret) > + return ERR_PTR(ret); > + ret = simpledrm_device_attach_genpd(sdev); > if (ret) > return ERR_PTR(ret); > > > --- > base-commit: 15d30b46573d75f5cb58cfacded8ebab9c76a2b0 > change-id: 20230910-simpledrm-multiple-power-domains-f41efa6ad9bc > > Best regards, > -- > Janne Grunau <j@xxxxxxxxxx> > > Reviewed-by: Neal Gompa <neal@xxxxxxxxx> -- 真実はいつも一つ！/ Always, there's only one truth!
