Re: [PATCH v2] phy: qcom-mipi-csi2: Add support for single power-domain SoCs

[Frank Li]

On Tue, Oct 27, 2026 at 10:20:47PM -0700, Anusha Arun Nandi wrote:
> sa8775p, qcs8300 and sc7280 each list exactly one power-domain ("top")
> on the CSI2 PHY node. For a device with a single power-domain phandle,
> the generic platform-bus code (platform_probe() ->
> dev_pm_domain_attach()) auto-attaches it via genpd_dev_pm_attach()
> before the driver's own probe() runs. phy_qcom_mipi_csi2_probe() then
> unconditionally calls devm_pm_domain_attach_list(), which fails with
> -EEXIST because dev->pm_domain is already set, and the driver treats
> that as fatal:
>
>   1. qcom-mipi-csi2-phy ace6000.phy: error -EEXIST: Failed to attach
>   power-domain list
>   2. qcom-mipi-csi2-phy ace6000.phy: probe with driver qcom-mipi-csi2-phy
>   failed with error -17
>
> x1e80100 is unaffected: it lists three power-domains, so the generic
> code does not auto-attach any of them (auto-attach only applies to
> single-power-domain devices); the driver's explicit attach is the
> only one that runs.
>
> For the single power-domain case, call dev_pm_domain_attach() instead
> of devm_pm_domain_attach_list(): it returns early when dev->pm_domain
> is already set, so csi2phy->pd_list is left NULL rather than built up
> by hand. The three call sites that walk pd_list for genpd
> performance-state scaling now guard against a NULL pd_list, which is
> harmless since scaling is unused (scaled = false) on every SoC that has
> a single "top" domain.
>
> Signed-off-by: Anusha Arun Nandi <anusha.nandi@xxxxxxxxxxxxxxxx>
> ---
>  drivers/phy/qualcomm/phy-qcom-mipi-csi2-core.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-mipi-csi2-core.c b/drivers/phy/qualcomm/phy-qcom-mipi-csi2-core.c
> index c0a4fa20eaf0..ac25e1e5f1c3 100644
> --- a/drivers/phy/qualcomm/phy-qcom-mipi-csi2-core.c
> +++ b/drivers/phy/qualcomm/phy-qcom-mipi-csi2-core.c
> @@ -43,7 +43,7 @@ phy_qcom_mipi_csi2_set_clock_rates(struct mipi_csi2phy_device *csi2phy,
>  	}
>
>  	pstate = 0;
> -	for (i = 0; i < csi2phy->pd_list->num_pds; i++) {
> +	for (i = 0; csi2phy->pd_list && i < csi2phy->pd_list->num_pds; i++) {
>  		unsigned int perf;
>
>  		if (!csi2phy->soc_cfg->genpds[i].scaled)
> @@ -174,7 +174,7 @@ static int phy_qcom_mipi_csi2_power_on(struct phy *phy)
>  unset_rate:
>  	dev_pm_opp_set_rate(csi2phy->dev, 0);
>
> -	for (i = 0; i < csi2phy->pd_list->num_pds; i++) {
> +	for (i = 0; csi2phy->pd_list && i < csi2phy->pd_list->num_pds; i++) {
>  		if (!csi2phy->soc_cfg->genpds[i].scaled)
>  			continue;
>
> @@ -204,7 +204,7 @@ static int phy_qcom_mipi_csi2_power_off(struct phy *phy)
>
>  	dev_pm_opp_set_rate(csi2phy->dev, 0);
>
> -	for (i = 0; i < csi2phy->pd_list->num_pds; i++) {
> +	for (i = 0; csi2phy->pd_list && i < csi2phy->pd_list->num_pds; i++) {
>  		if (!csi2phy->soc_cfg->genpds[i].scaled)
>  			continue;
>
> @@ -233,6 +233,10 @@ static int phy_qcom_mipi_csi2_attach_pm_domains(struct mipi_csi2phy_device *csi2
>  	const char **pd_names;
>  	int i;
>
> +	/* Single power-domain devices are already attached by the bus core. */
> +	if (csi2phy->soc_cfg->num_genpds == 1)
> +		return dev_pm_domain_attach(csi2phy->dev, 0);
> +

why call dev_pm_domain_attach() if Single power-domain devices are already
attached by the bus core?

Frank