Subject: Re: [PATCH v6 05/42] powerpc/powernv: Track IO/M32/M64 segments from PE

From: Alexey Kardashevskiy <[email-masked]>
Date: Wed, 12 Aug 2015 21:05:09 +1000

On 08/12/2015 08:45 PM, Gavin Shan wrote:
> On Tue, Aug 11, 2015 at 12:23:42PM +1000, Alexey Kardashevskiy wrote:
>> On 08/11/2015 10:03 AM, Gavin Shan wrote:
>>> On Mon, Aug 10, 2015 at 05:16:40PM +1000, Alexey Kardashevskiy wrote:
>>>> On 08/06/2015 02:11 PM, Gavin Shan wrote:
>>>>> The patch is adding 6 bitmaps, three to PE and three to PHB, to track
>>>>
>>>> The patch is also removing 2 arrays (io_segmap and m32_segmap), what is that
>>>> all about? Also, there was no m64_segmap, now there is, needs an explanation
>>>> may be.
>>>>
>>>
>>> Originally, the bitmaps (io_segmap and m32_segmap) are allocated dynamically.
>>> Now, they have fixed sizes - 512 bits.
>>>
>>> The subject "powerpc/powernv: Track IO/M32/M64 segments from PE" indicates
>>> why m64_segmap is added.
>>
>>
>> But before this patch, you somehow managed to keep it working without a map
>> for M64, by the same time you needed map for IO and M32. It seems you are
>> making things consistent in this patch but it also feels like you do not have
>> to do so as M64 did not need a map before and I cannot see why it needs one
>> now.
>>
>
> The M64 map is used by [PATCH v6 23/42] powerpc/powernv: Release PEs dynamically
> where the M64 segments consumed by one particular PE will be released.

Then add it where it is really started being used. It is really hard to 
review a patch which is actually spread between patches. Do not count that 
reviewers will just trust you.

>>>>
>>>>> the consumed by one particular PE, which can be released once the PE
>>>>> is destroyed during PCI unplugging time. Also, we're using fixed
>>>>> quantity of bits to trace the used IO, M32 and M64 segments by PEs
>>>>> in one particular PHB.
>>>>>
>>>>
>>>> Out of curiosity - have you considered having just 3 arrays, in PHB, storing
>>>> PE numbers, and ditching PE's arrays? Does PE itself need to know what PEs it
>>>> is using? Not sure about this master/slave PEs though.
>>>>
>>>
>>> I don't follow your suggestion. Can you rephrase and explain it a bit more?
>>
>>
>> Please explains in what situations you need same map in both PHB and PE and
>> how you are going to use them. For example, pe::m64_segmap and
>> phb::m64_segmap.
>>
>> I believe you need to know what segment is used by what PE and that's it and
>> having 2 bitmaps is overcomplicated hard to follow. Is there anything else
>> what I am missing?
>>
>
> The situation is same to all (IO, M32 and M64) segment maps. Taking m64_segmap
> as an example, it will be used when creating or destroying the PE who consumes
> M64 segments. phb::m64_segmap is recording the M64 segment usage in PHB's domain.
> It's used to check same M64 segment won't be used for towice. pe::m64_segmap tracks
> the M64 segments consumed by the PE.

You could have a single map in PHB, key would be a segment number and value 
would be PE number. No need to have a map in PE. At all. No need to 
initialize bitmaps, etc.

>>>> It would be easier to read patches if this one was right before
>>>> [PATCH v6 23/42] powerpc/powernv: Release PEs dynamically
>>>>
>>>
>>> I'll try to reoder the patch, but not expect too much...
>>>
>>>>
>>>>
>>>>> Signed-off-by: Gavin Shan <[email-masked]>
>>>>> ---
>>>>>   arch/powerpc/platforms/powernv/pci-ioda.c | 29 +++++++++++++++--------------
>>>>>   arch/powerpc/platforms/powernv/pci.h      | 18 ++++++++++++++----
>>>>>   2 files changed, 29 insertions(+), 18 deletions(-)
>>>>>
>>>>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>> index e4ac703..78b49a1 100644
>>>>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>> @@ -388,6 +388,12 @@ static int pnv_ioda_pick_m64_pe(struct pci_bus *bus, bool all)
>>>>>   			list_add_tail(&pe->list, &master_pe->slaves);
>>>>>   		}
>>>>>
>>>>> +		/* M64 segments consumed by slave PEs are tracked
>>>>> +		 * by master PE
>>>>> +		 */
>>>>> +		set_bit(pe->pe_number, master_pe->m64_segmap);
>>>>> +		set_bit(pe->pe_number, phb->ioda.m64_segmap);
>>>>> +
>>>>>   		/* P7IOC supports M64DT, which helps mapping M64 segment
>>>>>   		 * to one particular PE#. However, PHB3 has fixed mapping
>>>>>   		 * between M64 segment and PE#. In order to have same logic
>>>>> @@ -2871,9 +2877,11 @@ static void pnv_ioda_setup_pe_seg(struct pci_controller *hose,
>>>>>
>>>>>   			while (index < phb->ioda.total_pe &&
>>>>>   			       region.start <= region.end) {
>>>>> -				phb->ioda.io_segmap[index] = pe->pe_number;
>>>>> +				set_bit(index, pe->io_segmap);
>>>>> +				set_bit(index, phb->ioda.io_segmap);
>>>>>   				rc = opal_pci_map_pe_mmio_window(phb->opal_id,
>>>>> -					pe->pe_number, OPAL_IO_WINDOW_TYPE, 0, index);
>>>>> +					pe->pe_number, OPAL_IO_WINDOW_TYPE,
>>>>> +					0, index);
>>>>
>>>> Unrelated change.
>>>>
>>>
>>> True, will drop. However, checkpatch.pl will complain wtih:
>>> exceeding 80 characters.
>>
>> It will not as you are not changing these lines, it only complains on changes.
>>
>>
>>
>>>
>>>>>   				if (rc != OPAL_SUCCESS) {
>>>>>   					pr_err("%s: OPAL error %d when mapping IO "
>>>>>   					       "segment #%d to PE#%d\n",
>>>>> @@ -2896,9 +2904,11 @@ static void pnv_ioda_setup_pe_seg(struct pci_controller *hose,
>>>>>
>>>>>   			while (index < phb->ioda.total_pe &&
>>>>>   			       region.start <= region.end) {
>>>>> -				phb->ioda.m32_segmap[index] = pe->pe_number;
>>>>> +				set_bit(index, pe->m32_segmap);
>>>>> +				set_bit(index, phb->ioda.m32_segmap);
>>>>>   				rc = opal_pci_map_pe_mmio_window(phb->opal_id,
>>>>> -					pe->pe_number, OPAL_M32_WINDOW_TYPE, 0, index);
>>>>> +					pe->pe_number, OPAL_M32_WINDOW_TYPE,
>>>>> +					0, index);
>>>>
>>>> Unrelated change.
>>>>
>>>
>>> same as above.
>>>
>>>>>   				if (rc != OPAL_SUCCESS) {
>>>>>   					pr_err("%s: OPAL error %d when mapping M32 "
>>>>>   					       "segment#%d to PE#%d",
>>>>> @@ -3090,7 +3100,7 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>>>>>   {
>>>>>   	struct pci_controller *hose;
>>>>>   	struct pnv_phb *phb;
>>>>> -	unsigned long size, m32map_off, pemap_off, iomap_off = 0;
>>>>> +	unsigned long size, pemap_off;
>>>>>   	const __be64 *prop64;
>>>>>   	const __be32 *prop32;
>>>>>   	int len;
>>>>> @@ -3175,19 +3185,10 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>>>>>
>>>>>   	/* Allocate aux data & arrays. We don't have IO ports on PHB3 */
>>>>
>>>>
>>>> This comment came with if(IODA1) below, since you are removing the condition
>>>> below, makes sense to remove the comment as well or move it where people will
>>>> look for it (arch/powerpc/platforms/powernv/pci.h ?)
>>>>
>>>
>>> Yes, will do.
>>>
>>>>
>>>>>   	size = _ALIGN_UP(phb->ioda.total_pe / 8, sizeof(unsigned long));
>>>>> -	m32map_off = size;
>>>>> -	size += phb->ioda.total_pe * sizeof(phb->ioda.m32_segmap[0]);
>>>>> -	if (phb->type == PNV_PHB_IODA1) {
>>>>> -		iomap_off = size;
>>>>> -		size += phb->ioda.total_pe * sizeof(phb->ioda.io_segmap[0]);
>>>>> -	}
>>>>>   	pemap_off = size;
>>>>>   	size += phb->ioda.total_pe * sizeof(struct pnv_ioda_pe);
>>>>>   	aux = memblock_virt_alloc(size, 0);
>>>>
>>>>
>>>> After adding static arrays to PE and PHB, do you still need this "aux"?
>>>>
>>>
>>> "aux" is still needed to tell the boundary of pe_alloc_bitmap and pe_array.
>>>>
>>>>>   	phb->ioda.pe_alloc = aux;
>>>>> -	phb->ioda.m32_segmap = aux + m32map_off;
>>>>> -	if (phb->type == PNV_PHB_IODA1)
>>>>> -		phb->ioda.io_segmap = aux + iomap_off;
>>>>>   	phb->ioda.pe_array = aux + pemap_off;
>>>>>   	set_bit(phb->ioda.reserved_pe, phb->ioda.pe_alloc);
>>>>>
>>>>> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
>>>>> index 62239b1..08a4e57 100644
>>>>> --- a/arch/powerpc/platforms/powernv/pci.h
>>>>> +++ b/arch/powerpc/platforms/powernv/pci.h
>>>>> @@ -49,6 +49,15 @@ struct pnv_ioda_pe {
>>>>>   	/* PE number */
>>>>>   	unsigned int		pe_number;
>>>>>
>>>>> +	/* IO/M32/M64 segments consumed by the PE. Each PE can
>>>>> +	 * have one M64 segment at most, but M64 segments consumed
>>>>> +	 * by slave PEs will be contributed to the master PE. One
>>>>> +	 * PE can own multiple IO and M32 segments.
>>>>
>>>>
>>>> A PE can have multiple IO and M32 segments but just one M64 segment? Is this
>>>> correct for IODA1 or IODA2 or both? Is this a limitation of this
>>>> implementation or it comes from P7IOC/PHB3 hardware?
>>>>
>>>
>>> It's correct for IO and M32. However, on IODA1 or IODA2, one PE can have
>>> multiple M64 segments as well.
>>
>>
>> But the comment says "Each PE can have one M64 segment at most". Which
>> statement is correct?
>>
>
> The comment is correct regarding PHB's 15th M64 BAR: Each PE can have one
> M64 segment at post. It's from hardware limitation. However, once one PE
> consumes multiple M64 segments. all those M64 segments will be tracked in
> "master" PE and it's determined by software implementation.
>
>>>>> +	 */
>>>>> +	unsigned long		io_segmap[8];
>>>>> +	unsigned long		m32_segmap[8];
>>>>> +	unsigned long		m64_segmap[8];
>>>>
>>>> Magic constant "8", 64bit*8 = 512 PEs - where did this come from?
>>>>
>>>> Anyway,
>>>>
>>>> #define PNV_IODA_MAX_PE_NUM	512
>>>>
>>>> unsigned long io_segmap[PNV_IODA_MAX_PE_NUM/BITS_PER_LONG]
>>>>
>>>
>>> I prefer "8", not macro for 3 reasons:
>>> - The macro won't be used in the code.
>>
>> You will use it 6 times in the header, if you give it a good name, people
>> won't have to guess if the meaning of all these "8"s is the same and you
>> won't have to comment every use of it in this header file (now you have).
>>
>> Also, using BITS_PER_LONG tells the reader that this is a bitmask for sure.
>>
>>
>>> - The total segment number of specific resource is variable
>>>    on IODA1 and IODA2. I just choosed the max value with margin.
>>> - PNV_IODA_MAX_PE_NUM, indicating max PE number, isn't 512 on
>>>    IODA1 or IODA2.
>>
>> Give it a better name.
>>
>
> Ok. It it has to be a macro, then it's as below:
>
> #define PNV_IODA_MAX_SEG_NUM	512

Thanks mate :)

>>
>>>
>>>>> +
>>>>>   	/* "Weight" assigned to the PE for the sake of DMA resource
>>>>>   	 * allocations
>>>>>   	 */
>>>>> @@ -145,15 +154,16 @@ struct pnv_phb {
>>>>>   			unsigned int		io_segsize;
>>>>>   			unsigned int		io_pci_base;
>>>>>
>>>>> +			/* IO, M32, M64 segment maps */
>>>>> +			unsigned long		io_segmap[8];
>>>>> +			unsigned long		m32_segmap[8];
>>>>> +			unsigned long		m64_segmap[8];
>>>>> +
>>>>>   			/* PE allocation */
>>>>>   			struct mutex		pe_alloc_mutex;
>>>>>   			unsigned long		*pe_alloc;
>>>>>   			struct pnv_ioda_pe	*pe_array;
>>>>>
>>>>> -			/* M32 & IO segment maps */
>>>>> -			unsigned int		*m32_segmap;
>>>>> -			unsigned int		*io_segmap;
>>>>> -
>>>>>   			/* IRQ chip */
>>>>>   			int			irq_chip_init;
>>>>>   			struct irq_chip		irq_chip;
>>>>>
>
> Thanks,
> Gavin
>

-- 
Alexey