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Subject: Re: [PATCHv5 04/20] PCI: mobiveil: Remove the flag
 MSI_FLAG_MULTI_PCI_MSI
To:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        "Z.q. Hou" <zhiqiang.hou@nxp.com>
Cc:     "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        Xiaowei Bao <xiaowei.bao@nxp.com>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "l.subrahmanya@mobiveil.co.in" <l.subrahmanya@mobiveil.co.in>,
        "will.deacon@arm.com" <will.deacon@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Leo Li <leoyang.li@nxp.com>,
        "M.h. Lian" <minghuan.lian@nxp.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        Mingkai Hu <mingkai.hu@nxp.com>,
        "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
References: <20190412083635.33626-1-Zhiqiang.Hou@nxp.com>
 <20190412083635.33626-5-Zhiqiang.Hou@nxp.com>
 <20190611165935.GA22836@redmoon>
From:   Marc Zyngier <marc.zyngier@arm.com>
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Organization: ARM Ltd
Message-ID: <3b883516-1d63-1504-bdc9-22ac9c6f2d46@arm.com>
Date:   Tue, 11 Jun 2019 18:29:49 +0100
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On 11/06/2019 17:59, Lorenzo Pieralisi wrote:
> On Fri, Apr 12, 2019 at 08:35:36AM +0000, Z.q. Hou wrote:
>> From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
>>
>> The current code does not support multiple MSIs, so remove
>> the corresponding flag from the msi_domain_info structure.
> 
> Please explain me what's the problem before removing multi MSI
> support.

The reason seems to be the following code in the allocator:

        WARN_ON(nr_irqs != 1);
        mutex_lock(&msi->lock);

        bit = find_first_zero_bit(msi->msi_irq_in_use, msi->num_of_vectors);
        if (bit >= msi->num_of_vectors) {
                mutex_unlock(&msi->lock);
                return -ENOSPC;
        }

        set_bit(bit, msi->msi_irq_in_use);

So instead of fixing the allocator, the author prefers disabling
the feature. I'm not sure whether that is an acceptable outcome...

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...