linux-kernel - [PATCH v6 39/53] PCI: Allow bridge optional only io port resource required size to be 0

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Date:	Wed, 30 Sep 2015 22:53:13 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>, TJ <linux@....tj>,
	Yijing Wang <wangyijing@...wei.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH v6 39/53] PCI: Allow bridge optional only io port resource required size to be 0

When there is no child device under the non hotplug bridge,
We can use 0 for required size, and do not use old size as required size.

That will save some io port range for other bridges, as BIOS could do
some partial assign, and we want to use those not used io port range.

When there is child device, size will not be 0.
when the bridge supports hotplug, min_size will not be 0.
So they will still honor the old size as required size.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
 drivers/pci/setup-bus.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 0fd66b6..7a474d9 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1192,8 +1192,9 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 
 	size = size_aligned_for_isa(size);
 	size += size1;
-	size0 = calculate_size(size, min_size,
-			resource_size(b_res), min_align);
+	if (size || min_size)
+		size0 = calculate_size(size, min_size,
+					resource_size(b_res), min_align);
 	sum_add_size = size_aligned_for_isa(sum_add_size);
 	sum_add_size += sum_add_size1;
 	if (sum_add_size < min_sum_size)
@@ -1209,7 +1210,7 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 		return;
 	}
 
-	b_res->start = min_align;
+	b_res->start = size0 ? min_align : 0;
 	b_res->end = b_res->start + size0 - 1;
 	b_res->flags |= IORESOURCE_STARTALIGN;
 	if (size1 > size0 && realloc_head) {
-- 
1.8.4.5

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