Re: [PATCH] drm/xe/device: Discard check for lmem_init

["Summers, Stuart" <stuart.summers@intel.com>]

On Wed, 2025-12-17 at 18:21 +0530, Balasubramani Vivekanandan wrote:
> Prior to lmem init check, driver is waiting for the pcode uncore_init
> status. uncore_init status will be asserted after the complete boot
> and
> initialization of the SoC by the pcode. uncore_init confirms that
> lmem
> init and mmio unblock has been already completed.
> It makes no sense to check for lmem init after the pcode uncore_init
> check. So it can be removed.

Matt has some good comments here. I'm also a little worried about
firmware bugs in early bring-up where we might go through the pcode
init but be missing the PCI config updates associated with lmem_init.
This at least guarantees that we're checking that here.

Thanks,
Stuart

> 
> Signed-off-by: Balasubramani Vivekanandan
> <balasubramani.vivekanandan@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_device.c | 67 +++-----------------------------
> --
>  1 file changed, 5 insertions(+), 62 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device.c
> b/drivers/gpu/drm/xe/xe_device.c
> index 1197f914ef77..3818d0cccb0e 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -8,7 +8,6 @@
>  #include <linux/aperture.h>
>  #include <linux/delay.h>
>  #include <linux/fault-inject.h>
> -#include <linux/iopoll.h>
>  #include <linux/units.h>
>  
>  #include <drm/drm_atomic_helper.h>
> @@ -630,63 +629,6 @@ static int xe_set_dma_info(struct xe_device *xe)
>         return err;
>  }
>  
> -static int lmem_initializing(struct xe_device *xe)
> -{
> -       if (xe_mmio_read32(xe_root_tile_mmio(xe), GU_CNTL) &
> LMEM_INIT)
> -               return 0;
> -
> -       if (signal_pending(current))
> -               return -EINTR;
> -
> -       return 1;
> -}
> -
> -static int wait_for_lmem_ready(struct xe_device *xe)
> -{
> -       const unsigned long TIMEOUT_SEC = 60;
> -       unsigned long prev_jiffies;
> -       int initializing;
> -
> -       if (!IS_DGFX(xe))
> -               return 0;
> -
> -       if (IS_SRIOV_VF(xe))
> -               return 0;
> -
> -       if (!lmem_initializing(xe))
> -               return 0;
> -
> -       drm_dbg(&xe->drm, "Waiting for lmem initialization\n");
> -       prev_jiffies = jiffies;
> -
> -       /*
> -        * The boot firmware initializes local memory and
> -        * assesses its health. If memory training fails,
> -        * the punit will have been instructed to keep the GT powered
> -        * down.we won't be able to communicate with it
> -        *
> -        * If the status check is done before punit updates the
> register,
> -        * it can lead to the system being unusable.
> -        * use a timeout and defer the probe to prevent this.
> -        */
> -       poll_timeout_us(initializing = lmem_initializing(xe),
> -                       initializing <= 0,
> -                       20 * USEC_PER_MSEC, TIMEOUT_SEC *
> USEC_PER_SEC, true);
> -       if (initializing < 0)
> -               return initializing;
> -
> -       if (initializing) {
> -               drm_dbg(&xe->drm, "lmem not initialized by
> firmware\n");
> -               return -EPROBE_DEFER;
> -       }
> -
> -       drm_dbg(&xe->drm, "lmem ready after %ums",
> -               jiffies_to_msecs(jiffies - prev_jiffies));
> -
> -       return 0;
> -}
> -ALLOW_ERROR_INJECTION(wait_for_lmem_ready, ERRNO); /* See
> xe_pci_probe() */
> -
>  static void vf_update_device_info(struct xe_device *xe)
>  {
>         xe_assert(xe, IS_SRIOV_VF(xe));
> @@ -740,6 +682,11 @@ int xe_device_probe_early(struct xe_device *xe)
>         if (IS_SRIOV_VF(xe))
>                 vf_update_device_info(xe);
>  
> +       /*
> +        * Check for pcode uncore_init status to confirm if the SoC
> +        * initialization is complete. Until done, any MMIO or lmem
> access from
> +        * the driver will be blocked
> +        */
>         err = xe_pcode_probe_early(xe);
>         if (err || xe_survivability_mode_is_requested(xe)) {
>                 int save_err = err;
> @@ -756,10 +703,6 @@ int xe_device_probe_early(struct xe_device *xe)
>                 return save_err;
>         }
>  
> -       err = wait_for_lmem_ready(xe);
> -       if (err)
> -               return err;
> -
>         xe->wedged.mode = xe_modparam.wedged_mode;
>  
>         err = xe_device_vram_alloc(xe);