linux-kernel - Re: [PATCH v9 2/9] PCI: Using PCI configuration space header type instead of class type to assign resource

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Message-ID: <20181016145355.GB16390@e107981-ln.cambridge.arm.com>
Date:   Tue, 16 Oct 2018 15:53:55 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     honghui.zhang@...iatek.com
Cc:     bhelgaas@...gle.com, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, ryder.lee@...iatek.com,
        ulf.hansson@...aro.org, marc.zyngier@....com,
        matthias.bgg@...il.com, devicetree@...r.kernel.org,
        yingjoe.chen@...iatek.com, eddie.huang@...iatek.com,
        youlin.pei@...iatek.com, yt.shen@...iatek.com,
        jianjun.wang@...iatek.com
Subject: Re: [PATCH v9 2/9] PCI: Using PCI configuration space header type
 instead of class type to assign resource

On Tue, Oct 16, 2018 at 06:44:43PM +0800, honghui.zhang@...iatek.com wrote:
> From: Honghui Zhang <honghui.zhang@...iatek.com>
> 
> The PCI configuration space header type defines the layout of the rest
> of the header (PCI r3.0 sec 6.1, PCIe r4.0 sec 7.5.1.1.9) while the
> resource assignment is based on the configuration space layout instead
> of its class type. Using configuration space header type instead of
> class type for the resource assignment.
> 
> Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Honghui Zhang <honghui.zhang@...iatek.com>
> ---
>  drivers/pci/pci.c       |  3 +--
>  drivers/pci/probe.c     |  3 ---
>  drivers/pci/setup-bus.c | 20 ++++++++++----------
>  3 files changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 29ff961..7d379ca 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5908,8 +5908,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
>  	 * to enable the kernel to reassign new resource
>  	 * window later on.
>  	 */
> -	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE &&
> -	    (dev->class >> 8) == PCI_CLASS_BRIDGE_PCI) {
> +	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>  		for (i = PCI_BRIDGE_RESOURCES; i < PCI_NUM_RESOURCES; i++) {
>  			r = &dev->resource[i];
>  			if (!(r->flags & IORESOURCE_MEM))
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ec78400..29a35c1 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1695,9 +1695,6 @@ int pci_setup_device(struct pci_dev *dev)
>  		break;
>  
>  	case PCI_HEADER_TYPE_BRIDGE:		    /* bridge header */
> -		if (class != PCI_CLASS_BRIDGE_PCI)
> -			goto bad;
> -
>  		/*
>  		 * The PCI-to-PCI bridge spec requires that subtractive
>  		 * decoding (i.e. transparent) bridge must have programming
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 79b1824..69f90f4 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -182,7 +182,7 @@ static void __dev_sort_resources(struct pci_dev *dev,
>  	u16 class = dev->class >> 8;
>  
>  	/* Don't touch classless devices or host bridges or ioapics.  */
> -	if (class == PCI_CLASS_NOT_DEFINED || class == PCI_CLASS_BRIDGE_HOST)
> +	if (class == PCI_CLASS_NOT_DEFINED)

I think this check has been there since the first initial git commit,
whether that's _really_ needed or not in the current kernel it is very
hard to say.

I am not that sure it is safe to remove it, especially given that we are at
-rc8 and close to a release, it would be good if this patch could sit in
next to give it some exposure to testing before merging it upstream.

Lorenzo

>  		return;
>  
>  	/* Don't touch ioapic devices already enabled by firmware */
> @@ -1221,12 +1221,12 @@ void __pci_bus_size_bridges(struct pci_bus *bus, struct list_head *realloc_head)
>  		if (!b)
>  			continue;
>  
> -		switch (dev->class >> 8) {
> -		case PCI_CLASS_BRIDGE_CARDBUS:
> +		switch (dev->hdr_type) {
> +		case PCI_HEADER_TYPE_CARDBUS:
>  			pci_bus_size_cardbus(b, realloc_head);
>  			break;
>  
> -		case PCI_CLASS_BRIDGE_PCI:
> +		case PCI_HEADER_TYPE_BRIDGE:
>  		default:
>  			__pci_bus_size_bridges(b, realloc_head);
>  			break;
> @@ -1237,12 +1237,12 @@ void __pci_bus_size_bridges(struct pci_bus *bus, struct list_head *realloc_head)
>  	if (pci_is_root_bus(bus))
>  		return;
>  
> -	switch (bus->self->class >> 8) {
> -	case PCI_CLASS_BRIDGE_CARDBUS:
> +	switch (bus->self->hdr_type) {
> +	case PCI_HEADER_TYPE_CARDBUS:
>  		/* don't size cardbuses yet. */
>  		break;
>  
> -	case PCI_CLASS_BRIDGE_PCI:
> +	case PCI_HEADER_TYPE_BRIDGE:
>  		pci_bridge_check_ranges(bus);
>  		if (bus->self->is_hotplug_bridge) {
>  			additional_io_size  = pci_hotplug_io_size;
> @@ -1391,13 +1391,13 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
>  
>  		__pci_bus_assign_resources(b, realloc_head, fail_head);
>  
> -		switch (dev->class >> 8) {
> -		case PCI_CLASS_BRIDGE_PCI:
> +		switch (dev->hdr_type) {
> +		case PCI_HEADER_TYPE_BRIDGE:
>  			if (!pci_is_enabled(dev))
>  				pci_setup_bridge(b);
>  			break;
>  
> -		case PCI_CLASS_BRIDGE_CARDBUS:
> +		case PCI_HEADER_TYPE_CARDBUS:
>  			pci_setup_cardbus(b);
>  			break;
>  
> -- 
> 2.6.4
>