Re: [PATCH] drm/i915: add note on VLV/CHV hpll_freq and czclk_freq caching

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Sep 17, 2025 at 04:52:00PM +0300, Jani Nikula wrote:
> The caching at the initial read is a bit fragile in case, say, a further
> refactoring starts reading the frequencies at a time where it's not
> possible. Add a note about it.
> 
> Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/display/vlv_clock.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/vlv_clock.c b/drivers/gpu/drm/i915/display/vlv_clock.c
> index 2c55083d8fdb..42c2837b32c1 100644
> --- a/drivers/gpu/drm/i915/display/vlv_clock.c
> +++ b/drivers/gpu/drm/i915/display/vlv_clock.c
> @@ -8,6 +8,13 @@
>  #include "vlv_clock.h"
>  #include "vlv_sideband.h"
>  
> +/*
> + * FIXME: The caching of hpll_freq and czclk_freq relies on the first calls
> + * occurring at a time when they can actually be read. This appears to be the
> + * case, but is somewhat fragile. Make the initialization explicit at a point
> + * where they can be reliably read.
> + */
> +
>  /* returns HPLL frequency in kHz */
>  int vlv_clock_get_hpll_vco(struct drm_device *drm)
>  {
> -- 
> 2.47.3

-- 
Ville Syrjälä
Intel