netdev - Re: [PATCH net v2 1/1] net: ravb: Wait for operation mode to be applied

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Date: Wed, 27 Dec 2023 12:10:57 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Sergey Shtylyov <s.shtylyov@....ru>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 yoshihiro.shimoda.uh@...esas.com, wsa+renesas@...g-engineering.com,
 mitsuhiro.kimura.kc@...esas.com
Cc: netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH net v2 1/1] net: ravb: Wait for operation mode to be
 applied



On 23.12.2023 21:39, Sergey Shtylyov wrote:
> On 12/22/23 2:35 PM, Claudiu wrote:
> 
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> CSR.OPS bits specify the current operating mode and (according to
>> documentation) they are updated by HW when the operating mode change
>> request is processed. To comply with this check CSR.OPS before proceeding.
>>
>> Commit introduces ravb_set_opmode() that does all the necessities for
>> setting the operating mode (set DMA.CCC and wait for CSR.OPS) and call it
>> where needed. This should comply with all the HW manuals requirements as
>> different manual variants specify that different modes need to be checked
>> in CSR.OPS when setting DMA.CCC.
>>
>> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> ---
>>  drivers/net/ethernet/renesas/ravb_main.c | 52 ++++++++++++++----------
>>  1 file changed, 31 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index 664eda4b5a11..ae99d035a3b6 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -66,14 +66,15 @@ int ravb_wait(struct net_device *ndev, enum ravb_reg reg, u32 mask, u32 value)
>>  	return -ETIMEDOUT;
>>  }
>>  
>> -static int ravb_config(struct net_device *ndev)
>> +static int ravb_set_opmode(struct net_device *ndev, u32 opmode)
> 
>    Since you pass the complete CCC register value below, you should
> rather call the function ravb_set_ccc() and call the parameter opmode
> ccc.

This will be confusing. E.g., if renaming it ravb_set_ccc() one would
expect to set any fields of CCC though this function but this is not true
as ravb_modify() in this function masks only CCC_OPC. The call of:

error = ravb_set_opmode(ndev, CCC_OPC_CONFIG | CCC_GAC | CCC_CSEL_HPB);

bellow is just to comply with datasheet requirements, previous code and at
the same time re-use this function.

> 
>>  {
>> +	u32 csr_opmode = 1UL << opmode;
> 
>    Please use the correct expression, 1U << (ccc & CCC_OPC) instead.

Ok, good point.


> And I'd suggest calling the variable csr_ops or just ops.

ok

> 
>>  	int error;
>>  
>> -	/* Set config mode */
>> -	ravb_modify(ndev, CCC, CCC_OPC, CCC_OPC_CONFIG);
>> -	/* Check if the operating mode is changed to the config mode */
>> -	error = ravb_wait(ndev, CSR, CSR_OPS, CSR_OPS_CONFIG);
>> +	/* Set operating mode */
>> +	ravb_modify(ndev, CCC, CCC_OPC, opmode);
>> +	/* Check if the operating mode is changed to the requested one */
>> +	error = ravb_wait(ndev, CSR, CSR_OPS, csr_opmode);
>>  	if (error)
>>  		netdev_err(ndev, "failed to switch device to config mode\n");
> 
>    s/config/requested/? Or just print out that mode...
> 
> [...]
>> @@ -2560,21 +2559,23 @@ static int ravb_set_gti(struct net_device *ndev)
>>  	return 0;
>>  }
>>  
>> -static void ravb_set_config_mode(struct net_device *ndev)
>> +static int ravb_set_config_mode(struct net_device *ndev)
>>  {
>>  	struct ravb_private *priv = netdev_priv(ndev);
>>  	const struct ravb_hw_info *info = priv->info;
>> +	int error;
>>  
>>  	if (info->gptp) {
>> -		ravb_modify(ndev, CCC, CCC_OPC, CCC_OPC_CONFIG);
>> +		error = ravb_set_opmode(ndev, CCC_OPC_CONFIG);
> 
>    Don't we need to return on error here?

I kept it like this to have a single exit point from function. But probably
setting CSEL when OPC setup failed may lead to failures. I'll adjust it,
thanks.

> 
>>  		/* Set CSEL value */
>>  		ravb_modify(ndev, CCC, CCC_CSEL, CCC_CSEL_HPB);
>>  	} else if (info->ccc_gac) {
>> -		ravb_modify(ndev, CCC, CCC_OPC, CCC_OPC_CONFIG |
>> -			    CCC_GAC | CCC_CSEL_HPB);
>> +		error = ravb_set_opmode(ndev, CCC_OPC_CONFIG | CCC_GAC | CCC_CSEL_HPB);
> 
>    See, you pass more than just CCC.OPC value here -- need to mask it out
> above...

Agree.

> 
> [...]
>> @@ -2917,8 +2921,9 @@ static void ravb_remove(struct platform_device *pdev)
>>  	dma_free_coherent(ndev->dev.parent, priv->desc_bat_size, priv->desc_bat,
>>  			  priv->desc_bat_dma);
>>  
>> -	/* Set reset mode */
>> -	ravb_write(ndev, CCC_OPC_RESET, CCC);
>> +	error = ravb_set_opmode(ndev, CCC_OPC_RESET);
>> +	if (error)
>> +		netdev_err(ndev, "Failed to reset ndev\n");
> 
>    ravb_set_opmode() will have complained already at this point...
> 
> [...]
> 
> MBR, Sergey