Re: [PATCH] drm/xe/uc: Use u64 for offsets for which we use upper_32_bits()

[John Harrison <john.c.harrison@intel.com>]

On 3/18/2024 11:42, Daniele Ceraolo Spurio wrote:
> The GGTT is currently a 32 bit address space, but the HW and GuC
> support 48b addresses in GGTT-related operations, both to keep the
> interface/HW paths common between PPGTT and GGTT and to allow for
> future increase of the GGTT size.
> This leaves us having to program a 64b field with a 32b offset, which
> currently we're in some cases doing this by using an upper_32_bits()
> call on a 32b variable, which doesn't make any sense. To do this cleanly
> we have 2 options:
>
> 1 - Set the upper 32 bits directly to zero.
> 2 - Use 64b variables for the offset and keep programming the whole thing,
>      so we're ready if we ever have bigger offsets.
>
> This patch goes with option #2 and switches the related variables to u64.
>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: John Harrison <John.C.Harrison@Intel.com>
> ---
>   drivers/gpu/drm/xe/xe_guc.c          | 2 +-
>   drivers/gpu/drm/xe/xe_guc_hwconfig.c | 2 +-
>   drivers/gpu/drm/xe/xe_guc_submit.c   | 2 +-
>   drivers/gpu/drm/xe/xe_uc_fw.c        | 3 ++-
>   4 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
> index 9ed939c20602..1dfef2c29650 100644
> --- a/drivers/gpu/drm/xe/xe_guc.c
> +++ b/drivers/gpu/drm/xe/xe_guc.c
> @@ -74,7 +74,7 @@ static u32 guc_ctl_feature_flags(struct xe_guc *guc)
>   
>   static u32 guc_ctl_log_params_flags(struct xe_guc *guc)
>   {
> -	u32 offset = guc_bo_ggtt_addr(guc, guc->log.bo) >> PAGE_SHIFT;
> +	u64 offset = guc_bo_ggtt_addr(guc, guc->log.bo) >> PAGE_SHIFT;
This one does not do upper/lower(offset). The offset is simply shifted 
into a field position and OR'd into the u32 flags word below.

The whole flags construction should probably be updated to use the reg 
field macros, but I don't think making offset 64 bits gains anything here.

John.

>   	u32 flags;
>   
>   	#if (((CRASH_BUFFER_SIZE) % SZ_1M) == 0)
> diff --git a/drivers/gpu/drm/xe/xe_guc_hwconfig.c b/drivers/gpu/drm/xe/xe_guc_hwconfig.c
> index ea49f3885c10..525e51cc7aa7 100644
> --- a/drivers/gpu/drm/xe/xe_guc_hwconfig.c
> +++ b/drivers/gpu/drm/xe/xe_guc_hwconfig.c
> @@ -14,7 +14,7 @@
>   #include "xe_guc.h"
>   #include "xe_map.h"
>   
> -static int send_get_hwconfig(struct xe_guc *guc, u32 ggtt_addr, u32 size)
> +static int send_get_hwconfig(struct xe_guc *guc, u64 ggtt_addr, u32 size)
>   {
>   	u32 action[] = {
>   		XE_GUC_ACTION_GET_HWCONFIG,
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index d51cb9a4a6b7..9d3771ec5ceb 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -533,7 +533,7 @@ static void register_engine(struct xe_exec_queue *q)
>   	info.flags = CONTEXT_REGISTRATION_FLAG_KMD;
>   
>   	if (xe_exec_queue_is_parallel(q)) {
> -		u32 ggtt_addr = xe_lrc_parallel_ggtt_addr(lrc);
> +		u64 ggtt_addr = xe_lrc_parallel_ggtt_addr(lrc);
>   		struct iosys_map map = xe_lrc_parallel_map(lrc);
>   
>   		info.wq_desc_lo = lower_32_bits(ggtt_addr +
> diff --git a/drivers/gpu/drm/xe/xe_uc_fw.c b/drivers/gpu/drm/xe/xe_uc_fw.c
> index 44b8c5f58fd8..7e44c468eb0f 100644
> --- a/drivers/gpu/drm/xe/xe_uc_fw.c
> +++ b/drivers/gpu/drm/xe/xe_uc_fw.c
> @@ -788,7 +788,8 @@ static int uc_fw_xfer(struct xe_uc_fw *uc_fw, u32 offset, u32 dma_flags)
>   {
>   	struct xe_device *xe = uc_fw_to_xe(uc_fw);
>   	struct xe_gt *gt = uc_fw_to_gt(uc_fw);
> -	u32 src_offset, dma_ctrl;
> +	u64 src_offset;
> +	u32 dma_ctrl;
>   	int ret;
>   
>   	xe_force_wake_assert_held(gt_to_fw(gt), XE_FW_GT);