linux-kernel - Re: [PATCH v2] net: stmmac: explicitly deassert GMAC_AHB

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Date:   Tue, 8 Jun 2021 19:57:00 +0100
From:   Matthew Hagan <mnhagan88@...il.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     bjorn.andersson@...aro.org,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Wong Vee Khee <vee.khee.wong@...ux.intel.com>,
        Tan Tee Min <tee.min.tan@...el.com>,
        "Wong, Vee Khee" <vee.khee.wong@...el.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: stmmac: explicitly deassert GMAC_AHB_RESET

On 07/06/2021 10:45, Philipp Zabel wrote:

> On Sun, 2021-06-06 at 11:30 +0100, Matthew Hagan wrote:
>> We are currently assuming that GMAC_AHB_RESET will already be deasserted
>> by the bootloader. However if this has not been done, probing of the GMAC
>> will fail. To remedy this we must ensure GMAC_AHB_RESET has been deasserted
>> prior to probing.
>>
>> v2 changes:
>>  - remove NULL condition check for stmmac_ahb_rst in stmmac_main.c
>>  - unwrap dev_err() message in stmmac_main.c
>>  - add PTR_ERR() around plat->stmmac_ahb_rst in stmmac_platform.c
>>
>> Signed-off-by: Matthew Hagan <mnhagan88@...il.com>
>> ---
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     | 4 ++++
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 7 +++++++
>>  include/linux/stmmac.h                                | 1 +
>>  3 files changed, 12 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 6d41dd6f9f7a..0d4cb423cbbd 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -6840,6 +6840,10 @@ int stmmac_dvr_probe(struct device *device,
>>  			reset_control_reset(priv->plat->stmmac_rst);
>>  	}
>>  
>> +	ret = reset_control_deassert(priv->plat->stmmac_ahb_rst);
>> +	if (ret == -ENOTSUPP)
>> +		dev_err(priv->device, "unable to bring out of ahb reset\n");
>> +
> I would make this
>
> 	if (ret)
> 		dev_err(priv->device, "unable to bring out of ahb reset: %pe\n", ERR_PTR(ret));

Done.

>
> Also consider asserting the reset again in the remove path. Or is there
> a reason not to?

Don't see any issue doing this. As this is a shared reset, the assert will only occur
when the final GMAC is removed, due to the tracking of deassert_count.

> With that addressed,
>
> Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>
>
> regards
> Philipp

Thanks,

Matthew