Re: [PATCH v2] net: stmmac: explicitly deassert GMAC_AHB_RESET

From: Matthew Hagan <mnhagan88@gmail.com>
To: Philipp Zabel <p.zabel@pengutronix.de>
Cc: bjorn.andersson@linaro.org,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Voon Weifeng <weifeng.voon@intel.com>,
	Ong Boon Leong <boon.leong.ong@intel.com>,
	Wong Vee Khee <vee.khee.wong@linux.intel.com>,
	Tan Tee Min <tee.min.tan@intel.com>,
	"Wong, Vee Khee" <vee.khee.wong@intel.com>,
	Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] net: stmmac: explicitly deassert GMAC_AHB_RESET
Date: Tue, 8 Jun 2021 19:57:00 +0100	[thread overview]
Message-ID: <c223051b-c11c-3c08-055b-544f9e31cf00@gmail.com> (raw)
In-Reply-To: <b89d828a08528aaa07e3527d254785f1e40b9bee.camel@pengutronix.de>

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@gmail.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@pengutronix.de>
>
> regards
> Philipp

Thanks,

Matthew

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