[PATCH net v4] net: airoha: Add retry mechanism to airoha_qdma_set_trtcm_param()

[PATCH net v4] net: airoha: Add retry mechanism to airoha_qdma_set_trtcm_param()

[Christian Marangi]

From: Leto Liu (刘涛) <Leto.Liu@airoha.com>

CPU accesses QDMA via the bus. When multiple modules are using the bus
simultaneously, CPU access to QDMA may encounter bus timeouts and fails,
resulting in QDMA configuration failures and potentially causing packet
transmission issues. In order to mitigate the issue, introduce a retry
mechanism to airoha_qdma_set_trtcm_param routine in order to ensure the
configuration is correctly applied to the hardware.

Fixes: ef1ca9271313b ("net: airoha: Add sched HTB offload support")
Signed-off-by: Leto Liu (刘涛) <Leto.Liu@airoha.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
Changes v4:
- Rebase on top of net
Changes v3:
- Init data
- Use continue instead of negative error for poll
- Add memory block after CFG_PARAM

 drivers/net/ethernet/airoha/airoha_eth.c | 29 +++++++++++++++++++-----
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 79418e682f71..302f8c432055 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -2712,14 +2712,31 @@ static int airoha_qdma_set_trtcm_param(struct airoha_qdma *qdma, int channel,
 		     FIELD_PREP(TRTCM_METER_GROUP_MASK, group) |
 		     FIELD_PREP(TRTCM_PARAM_INDEX_MASK, idx) |
 		     FIELD_PREP(TRTCM_PARAM_RATE_TYPE_MASK, mode);
+	int i;
 
-	airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
-	airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);
+	for (i = 0; i < 100; i++) {
+		u32 data = 0;
 
-	return read_poll_timeout(airoha_qdma_rr, val,
-				 val & TRTCM_PARAM_RW_DONE_MASK,
-				 USEC_PER_MSEC, 10 * USEC_PER_MSEC, true,
-				 qdma, REG_TRTCM_CFG_PARAM(addr));
+		airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
+		wmb();
+		airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);
+		wmb();
+
+		if (read_poll_timeout(airoha_qdma_rr, data,
+				      data & TRTCM_PARAM_RW_DONE_MASK,
+				      USEC_PER_MSEC, 10 * USEC_PER_MSEC,
+				      true, qdma, REG_TRTCM_CFG_PARAM(addr)))
+			continue;
+
+		if (airoha_qdma_get_trtcm_param(qdma, channel, addr, param,
+						mode, &data, NULL))
+			continue;
+
+		if (data == val)
+			return 0;
+	}
+
+	return -EBUSY;
 }
 
 static int airoha_qdma_set_trtcm_config(struct airoha_qdma *qdma, int channel,
-- 
2.53.0

Re: [PATCH net v4] net: airoha: Add retry mechanism to airoha_qdma_set_trtcm_param()

[Jakub Kicinski]

On Mon, 17 Aug 2026 09:50:39 +0200 Christian Marangi wrote:
> CPU accesses QDMA via the bus. 

Maybe it's just me but I have no idea what "the bus" is here.
I'm guessing that the bug is that the CSR write path to 
some SRAM may get starved.

> When multiple modules are using the bus
> simultaneously, CPU access to QDMA may encounter bus timeouts and fails,
> resulting in QDMA configuration failures and potentially causing packet
> transmission issues. In order to mitigate the issue, introduce a retry
> mechanism to airoha_qdma_set_trtcm_param routine in order to ensure the
> configuration is correctly applied to the hardware.
> 
> Fixes: ef1ca9271313b ("net: airoha: Add sched HTB offload support")
> Signed-off-by: Leto Liu (刘涛) <Leto.Liu@airoha.com>
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> ---
> Changes v4:
> - Rebase on top of net
> Changes v3:
> - Init data
> - Use continue instead of negative error for poll
> - Add memory block after CFG_PARAM
> 
>  drivers/net/ethernet/airoha/airoha_eth.c | 29 +++++++++++++++++++-----
>  1 file changed, 23 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 79418e682f71..302f8c432055 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -2712,14 +2712,31 @@ static int airoha_qdma_set_trtcm_param(struct airoha_qdma *qdma, int channel,
>  		     FIELD_PREP(TRTCM_METER_GROUP_MASK, group) |
>  		     FIELD_PREP(TRTCM_PARAM_INDEX_MASK, idx) |
>  		     FIELD_PREP(TRTCM_PARAM_RATE_TYPE_MASK, mode);
> +	int i;
>  
> -	airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
> -	airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);

a short two-line comment would help remind why we're doing this loop
here, specifically (and not all register accesses)

> +	for (i = 0; i < 100; i++) {
> +		u32 data = 0;
>  
> -	return read_poll_timeout(airoha_qdma_rr, val,
> -				 val & TRTCM_PARAM_RW_DONE_MASK,
> -				 USEC_PER_MSEC, 10 * USEC_PER_MSEC, true,
> -				 qdma, REG_TRTCM_CFG_PARAM(addr));
> +		airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
> +		wmb();
> +		airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);
> +		wmb();

The wmb()s look like cargo cult, please drop them or explain what they
do.

> +		if (airoha_qdma_get_trtcm_param(qdma, channel, addr, param,
> +						mode, &data, NULL))
> +			continue;

AI also points out that we're worried about this get timing out here
but other spots in the driver read it without a retry. Is this possibly
also an unnecessary check, like the wmb()?
-- 
pw-bot: cr