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Message-ID: <5a308d21-d463-4d6f-b5d3-95a0c2ede2c1@oss.qualcomm.com>
Date: Tue, 18 Nov 2025 17:35:09 +0800
From: Baochen Qiang <baochen.qiang@....qualcomm.com>
To: Alexander Wilhelm <alexander.wilhelm@...termo.com>,
Jeff Johnson <jjohnson@...nel.org>
Cc: linux-wireless@...r.kernel.org, ath12k@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wifi: ath12k: fix endianness handling for SRNG ring
pointer accesses
On 11/18/2025 3:21 PM, Alexander Wilhelm wrote:
> The SRNG head and tail ring pointers are stored in device memory as
> little-endian values. On big-endian systems, direct dereferencing of these
> pointers leads to incorrect values being read or written, causing ring
> management issues and potentially breaking data flow.
>
> This patch ensures all accesses to SRNG ring pointers use the appropriate
> endianness conversions. This affects both read and write paths for source
> and destination rings, as well as debug output. The changes guarantee
> correct operation on both little- and big-endian architectures.
>
> Signed-off-by: Alexander Wilhelm <alexander.wilhelm@...termo.com>
> ---
> drivers/net/wireless/ath/ath12k/hal.c | 35 +++++++++++++++------------
> 1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath12k/hal.c b/drivers/net/wireless/ath/ath12k/hal.c
> index 6406fcf5d69f..bd4d1de9eb1a 100644
> --- a/drivers/net/wireless/ath/ath12k/hal.c
> +++ b/drivers/net/wireless/ath/ath12k/hal.c
> @@ -2007,7 +2007,7 @@ int ath12k_hal_srng_dst_num_free(struct ath12k_base *ab, struct hal_srng *srng,
> tp = srng->u.dst_ring.tp;
>
> if (sync_hw_ptr) {
> - hp = *srng->u.dst_ring.hp_addr;
> + hp = le32_to_cpu(*srng->u.dst_ring.hp_addr);
should we also need to change its type to '__le32 *'?
> srng->u.dst_ring.cached_hp = hp;
> } else {
> hp = srng->u.dst_ring.cached_hp;
> @@ -2030,7 +2030,7 @@ int ath12k_hal_srng_src_num_free(struct ath12k_base *ab, struct hal_srng *srng,
> hp = srng->u.src_ring.hp;
>
> if (sync_hw_ptr) {
> - tp = *srng->u.src_ring.tp_addr;
> + tp = le32_to_cpu(*srng->u.src_ring.tp_addr);
> srng->u.src_ring.cached_tp = tp;
> } else {
> tp = srng->u.src_ring.cached_tp;
> @@ -2149,9 +2149,9 @@ void ath12k_hal_srng_access_begin(struct ath12k_base *ab, struct hal_srng *srng)
>
> if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
> srng->u.src_ring.cached_tp =
> - *(volatile u32 *)srng->u.src_ring.tp_addr;
> + le32_to_cpu(*(volatile u32 *)srng->u.src_ring.tp_addr);
> } else {
> - hp = READ_ONCE(*srng->u.dst_ring.hp_addr);
> + hp = le32_to_cpu(READ_ONCE(*srng->u.dst_ring.hp_addr));
>
> if (hp != srng->u.dst_ring.cached_hp) {
> srng->u.dst_ring.cached_hp = hp;
> @@ -2175,25 +2175,28 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
> * hence written to a shared memory location that is read by FW
> */
> if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
> - srng->u.src_ring.last_tp =
> - *(volatile u32 *)srng->u.src_ring.tp_addr;
> + srng->u.src_ring.last_tp = le32_to_cpu(
> + *(volatile u32 *)srng->u.src_ring.tp_addr);
> /* Make sure descriptor is written before updating the
> * head pointer.
> */
> dma_wmb();
> - WRITE_ONCE(*srng->u.src_ring.hp_addr, srng->u.src_ring.hp);
> + WRITE_ONCE(*srng->u.src_ring.hp_addr,
> + cpu_to_le32(srng->u.src_ring.hp));
> } else {
> - srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
> + srng->u.dst_ring.last_hp =
> + le32_to_cpu(*srng->u.dst_ring.hp_addr);
> /* Make sure descriptor is read before updating the
> * tail pointer.
> */
> dma_mb();
> - WRITE_ONCE(*srng->u.dst_ring.tp_addr, srng->u.dst_ring.tp);
> + WRITE_ONCE(*srng->u.dst_ring.tp_addr,
> + cpu_to_le32(srng->u.dst_ring.tp));
> }
> } else {
> if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
> - srng->u.src_ring.last_tp =
> - *(volatile u32 *)srng->u.src_ring.tp_addr;
> + srng->u.src_ring.last_tp = le32_to_cpu(
> + *(volatile u32 *)srng->u.src_ring.tp_addr);
> /* Assume implementation use an MMIO write accessor
> * which has the required wmb() so that the descriptor
> * is written before the updating the head pointer.
> @@ -2203,7 +2206,8 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
> (unsigned long)ab->mem,
> srng->u.src_ring.hp);
> } else {
> - srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
> + srng->u.dst_ring.last_hp =
> + le32_to_cpu(*srng->u.dst_ring.hp_addr);
> /* Make sure descriptor is read before updating the
> * tail pointer.
> */
> @@ -2547,7 +2551,7 @@ void ath12k_hal_srng_shadow_update_hp_tp(struct ath12k_base *ab,
> * HP only when then ring isn't' empty.
> */
> if (srng->ring_dir == HAL_SRNG_DIR_SRC &&
> - *srng->u.src_ring.tp_addr != srng->u.src_ring.hp)
> + le32_to_cpu(*srng->u.src_ring.tp_addr) != srng->u.src_ring.hp)
> ath12k_hal_srng_access_end(ab, srng);
> }
>
> @@ -2648,14 +2652,15 @@ void ath12k_hal_dump_srng_stats(struct ath12k_base *ab)
> "src srng id %u hp %u, reap_hp %u, cur tp %u, cached tp %u last tp %u napi processed before %ums\n",
> srng->ring_id, srng->u.src_ring.hp,
> srng->u.src_ring.reap_hp,
> - *srng->u.src_ring.tp_addr, srng->u.src_ring.cached_tp,
> + __le32_to_cpu(*srng->u.src_ring.tp_addr),
> + srng->u.src_ring.cached_tp,
> srng->u.src_ring.last_tp,
> jiffies_to_msecs(jiffies - srng->timestamp));
> else if (srng->ring_dir == HAL_SRNG_DIR_DST)
> ath12k_err(ab,
> "dst srng id %u tp %u, cur hp %u, cached hp %u last hp %u napi processed before %ums\n",
> srng->ring_id, srng->u.dst_ring.tp,
> - *srng->u.dst_ring.hp_addr,
> + __le32_to_cpu(*srng->u.dst_ring.hp_addr),
why __le32_to_cpu() only in logging, while le32_to_cpu() elsewhere?
> srng->u.dst_ring.cached_hp,
> srng->u.dst_ring.last_hp,
> jiffies_to_msecs(jiffies - srng->timestamp));
>
> base-commit: be83ff7549057d184b693a85cafc10fbd520f3d7
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