From 3078d9c8b6a0939bc732fd1c36ef86c0178127dd Mon Sep 17 00:00:00 2001 From: Michal Wajdeczko Date: Tue, 2 Jul 2024 20:37:04 +0200 Subject: [PATCH] drm/xe: Use VF_CAP_REG for device wmb To force a write barrier on the device memory, we write to the SOFTWARE_FLAGS_SPR33 register, but this particular register was selected because it was one of the writable and unused register. Since a write barrier should also work if we use the read-only register, switch to VF_CAP_REG register that is also marked as accessible for VFs. While at it, add simple kernel-doc for xe_device_wmb() function. Signed-off-by: Michal Wajdeczko Cc: Matt Roper Reviewed-by: Matt Roper Reviewed-by: Himal Prasad Ghimiray Link: https://patchwork.freedesktop.org/patch/msgid/20240702183704.1022-4-michal.wajdeczko@intel.com --- drivers/gpu/drm/xe/xe_device.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c index 03492fbcb8fbf..db513175b29e7 100644 --- a/drivers/gpu/drm/xe/xe_device.c +++ b/drivers/gpu/drm/xe/xe_device.c @@ -744,13 +744,22 @@ void xe_device_shutdown(struct xe_device *xe) { } +/** + * xe_device_wmb() - Device specific write memory barrier + * @xe: the &xe_device + * + * While wmb() is sufficient for a barrier if we use system memory, on discrete + * platforms with device memory we additionally need to issue a register write. + * Since it doesn't matter which register we write to, use the read-only VF_CAP + * register that is also marked as accessible by the VFs. + */ void xe_device_wmb(struct xe_device *xe) { struct xe_gt *gt = xe_root_mmio_gt(xe); wmb(); if (IS_DGFX(xe)) - xe_mmio_write32(gt, SOFTWARE_FLAGS_SPR33, 0); + xe_mmio_write32(gt, VF_CAP_REG, 0); } /** -- 2.49.0