Re: [PATCH] drm/i915/cx0_phy: Fix ARL-S host bridge detection

["Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com>]

On 9/16/2026 8:59 PM, Dnyaneshwar Bhadane wrote:
> is_arrowlake_s_by_host_bridge() re-assigned pdev in the while()
> exited (that's the loop's exit condition). This made
> condition itself, so pdev was always NULL by the time the loop
> "return pdev && ..." always false, so an Arrow Lake S host bridge
> was never detected and intel_c20_hdmi_tmds_tx_cgf_1() always used
> the wrong tx_misc value for that platform.
> 
> Check the ID as each host bridge is enumerated instead of after the
> loop, and drop the reference pci_get_class() took on the matching
> device before returning.
> 

The commit message is quite obfuscated. Also needs a cc stable.

Other than that, LGTM.

Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>


> Suggested-by: Jani Nikula <jani.nikula@intel.com>
> Fixes: 3630a47b700e ("drm/i915/cx0_phy: Update HDMI TMDS C20 algorithm value")
> Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_cx0_phy.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
> index dbebd7210848..de450ebf541f 100644
> --- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
> @@ -2342,12 +2342,14 @@ static void intel_c10pll_dump_hw_state(struct drm_printer *p,
>   static bool is_arrowlake_s_by_host_bridge(void)
>   {
>   	struct pci_dev *pdev = NULL;
> -	u16 host_bridge_pci_dev_id;
> -
> -	while ((pdev = pci_get_class(PCI_CLASS_BRIDGE_HOST << 8, pdev)))
> -		host_bridge_pci_dev_id = pdev->device;
> +	while ((pdev = pci_get_class(PCI_CLASS_BRIDGE_HOST << 8, pdev))) {
> +		if (IS_ARROWLAKE_S_BY_HOST_BRIDGE_ID(pdev->device)) {
> +			pci_dev_put(pdev);
> +			return true;
> +		}
> +	}
>   
> -	return pdev && IS_ARROWLAKE_S_BY_HOST_BRIDGE_ID(host_bridge_pci_dev_id);
> +	return false;
>   }
>   
>   static u16 intel_c20_hdmi_tmds_tx_cgf_1(struct intel_display *display)