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    SubjectRe: [PATCH] drm/simpledrm: Add support for multiple "power-domains"
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    Le 10/09/2023 à 18:39, Janne Grunau via B4 Relay a écrit :
    > From: Janne Grunau <j@jannau.net>
    >
    > 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@jannau.net>
    > ---
    > drivers/gpu/drm/tiny/simpledrm.c | 106 +++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 106 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
    > index ff86ba1ae1b8..efedede57d42 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 +475,102 @@ 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 = /*(struct simpledrm_device *)*/res;
    > +
    > +
    > + drm_err(&sdev->dev, "% power-domains count:%d\n", __func__, sdev->pwr_dom_count);
    > + 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 PTR_ERR(sdev->pwr_dom_devs[i]);
    > + }
    > + drm_err(&sdev->dev,
    > + "pm_domain_attach_by_id(%u) failed: %d\n", i, ret);
    > + }
    > +

    sdev->pwr_dom_devs[i] can be an ERR_PTR here.
    Maybe a break or a continue missing after drm_err() above?

    CJ

    > + 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_err(&sdev->dev, "failed to link power-domain %u\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 +754,9 @@ 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,

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