linux-kernel - Re: [PATCH] PCI: dwc: designware: don't sleep in atomic context

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Message-ID: <70cd34bd-01db-cd93-ddf7-d82114ccc61a@samsung.com>
Date:   Fri, 13 Oct 2017 09:10:38 +0530
From:   Pankaj Dubey <pankaj.dubey@...sung.com>
To:     David Laight <David.Laight@...LAB.COM>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>
Subject: Re: [PATCH] PCI: dwc: designware: don't sleep in atomic context



On 10/12/2017 04:09 PM, David Laight wrote:
> From: Pankaj Dubey
>> Sent: 12 October 2017 08:55
>> In pcie-designware.c many places we are calling "usleep_range" which
>> are in atomic context. This patch fixes these potential BUGs and
>> replaces "usleep_range" with mdelay calls.
>>
>> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
>> ---
>>   drivers/pci/dwc/pcie-designware.c | 8 ++++----
>>   drivers/pci/dwc/pcie-designware.h | 3 +--
>>   2 files changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/dwc/pcie-designware.c b/drivers/pci/dwc/pcie-designware.c
>> index 88abddd..35d19b9 100644
>> --- a/drivers/pci/dwc/pcie-designware.c
>> +++ b/drivers/pci/dwc/pcie-designware.c
>> @@ -138,7 +138,7 @@ static void dw_pcie_prog_outbound_atu_unroll(struct dw_pcie *pci, int index,
>>   		if (val & PCIE_ATU_ENABLE)
>>   			return;
>>
>> -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
>> +		mdelay(LINK_WAIT_IATU_MIN);
>>   	}
> Spinning for 9ms (possibly 10 times) isn't really a good idea.

Yes. It may not be a good idea, however in our experiment it never hit 
maximum retry count.
I just converted usleep_range to mdelay keeping min time limitation as 
it is, though I
am not sure, how do we arrived on these numbers in original code, may be 
Joao Pinto
from Synopsys have some idea, I will try to do few experiment and try to 
find out what
is sufficient minimum time in our hardware for these mdelay.

Thanks,
Pankaj Dubey
> 	David
>
>
>
>