linux-kernel - Re: [PATCH 2/4] powerpc/pseries/iommu: Implement ibm,reset-pe-dma-windows rtas call

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Message-ID: <c02fbebb-32ed-f328-ff93-ab2201844d61@ozlabs.ru>
Date:   Tue, 23 Jun 2020 11:11:59 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] powerpc/pseries/iommu: Implement
 ibm,reset-pe-dma-windows rtas call



On 23/06/2020 04:58, Leonardo Bras wrote:
> Hello Alexey, thanks for the feedback!
> 
> On Mon, 2020-06-22 at 20:02 +1000, Alexey Kardashevskiy wrote:
>>
>> On 19/06/2020 15:06, Leonardo Bras wrote:
>>> Platforms supporting the DDW option starting with LoPAR level 2.7 implement
>>> ibm,ddw-extensions. The first extension available (index 2) carries the
>>> token for ibm,reset-pe-dma-windows rtas call, which is used to restore
>>> the default DMA window for a device, if it has been deleted.
>>>
>>> It does so by resetting the TCE table allocation for the PE to it's
>>> boot time value, available in "ibm,dma-window" device tree node.
>>>
>>> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
>>> ---
>>>  arch/powerpc/platforms/pseries/iommu.c | 33 ++++++++++++++++++++++++++
>>>  1 file changed, 33 insertions(+)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>>> index e5a617738c8b..5e1fbc176a37 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -1012,6 +1012,39 @@ static phys_addr_t ddw_memory_hotplug_max(void)
>>>  	return max_addr;
>>>  }
>>>  
>>> +/*
>>> + * Platforms supporting the DDW option starting with LoPAR level 2.7 implement
>>> + * ibm,ddw-extensions, which carries the rtas token for
>>> + * ibm,reset-pe-dma-windows.
>>> + * That rtas-call can be used to restore the default DMA window for the device.
>>> + */
>>> +static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
>>> +{
>>> +	int ret;
>>> +	u32 cfg_addr, ddw_ext[3];
>>> +	u64 buid;
>>> +	struct device_node *dn;
>>> +	struct pci_dn *pdn;
>>> +
>>> +	ret = of_property_read_u32_array(par_dn, "ibm,ddw-extensions",
>>> +					 &ddw_ext[0], 3);
>>
>> s/3/2/ as for the reset extension you do not need the "64bit largest
>> block" extension.
> 
> Sure, I will update this.
> 
>>
>>
>>> +	if (ret)
>>> +		return;
>>> +
>>> +	dn = pci_device_to_OF_node(dev);
>>> +	pdn = PCI_DN(dn);
>>> +	buid = pdn->phb->buid;
>>> +	cfg_addr = ((pdn->busno << 16) | (pdn->devfn << 8));
>>> +
>>> +	ret = rtas_call(ddw_ext[1], 3, 1, NULL, cfg_addr,
>>
>> Here the "reset" extention is in ddw_ext[1]. Hm. 1/4 has a bug then.
> 
> Humm, in 1/4 I used dd_ext[0] (how many extensions) and ddw_ext[2] (64-
> bit largest window count). I fail to see the bug here.

There is none, my bad :)


>> And I am pretty sure it won't compile as reset_dma_window() is not used
>> and it is static so fold it into one the next patches. Thanks,
> 
> Sure, I will do that. 
> I was questioning myself about this and thought it would be better to
> split for easier revision.

People separate things when a patch is really huge but even then I miss
the point - I'd really like to see a new function _and_ its uses in the
same patch, otherwise I either need to jump between mails or apply the
series, either is little but extra work :) Thanks,


>>
>>
>>> +			BUID_HI(buid), BUID_LO(buid));
>>> +	if (ret)
>>> +		dev_info(&dev->dev,
>>> +			 "ibm,reset-pe-dma-windows(%x) %x %x %x returned %d ",
>>> +			 ddw_ext[1], cfg_addr, BUID_HI(buid), BUID_LO(buid),
>>> +			 ret);
>>> +}
>>> +
>>>  /*
>>>   * If the PE supports dynamic dma windows, and there is space for a table
>>>   * that can map all pages in a linear offset, then setup such a table,
>>>
> 
> Best regards,
> Leonardo
> 

-- 
Alexey