Re: [PATCH V4 06/16] PCI: dwc: Add ext config space capability search API

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On 4/24/2019 2:05 AM, Bjorn Helgaas wrote:
On Tue, Apr 23, 2019 at 01:57:20PM +0530, Vidya Sagar wrote:
Add extended configuration space capability search API using struct dw_pcie *
pointer

Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
Acked-by: Gustavo Pimentel <gustavo.pimentel@xxxxxxxxxxxx>
---
Changes from [v3]:
* None

Changes from [v2]:
* None

Changes from [v1]:
* This is a new patch in v2 series

  drivers/pci/controller/dwc/pcie-designware.c | 41 ++++++++++++++++++++
  drivers/pci/controller/dwc/pcie-designware.h |  1 +
  2 files changed, 42 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 6a98135244d6..ecf5fe8842f6 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -53,6 +53,47 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
  	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
  }

Please make sure there's a comment here about why
pci_find_ext_capability() can't be used (a comment covering both this
and pci_find_capability() is fine, if the reason is the same).
Reason is same that standard pci_find_ext_capability() uses 'struct pci_dev *dev' pointer
and can only be used post enumeration whereas APIs being added here use 'struct dw_pcie *pci'
and can be used before link up also.
I'll add a comment in the other patch where I'm moving these APIs from pcie-designware-ep.c file
to pcie-designware.c file.


+static int dw_pcie_find_next_ext_capability(struct dw_pcie *pci, int start,
+					    int cap)
+{
+	u32 header;
+	int ttl;
+	int pos = PCI_CFG_SPACE_SIZE;
+
+	/* minimum 8 bytes per capability */
+	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
+
+	if (start)
+		pos = start;
+
+	header = dw_pcie_readl_dbi(pci, pos);
+	/*
+	 * If we have no capabilities, this is indicated by cap ID,
+	 * cap version and next pointer all being 0.
+	 */
+	if (header == 0)
+		return 0;
+
+	while (ttl-- > 0) {
+		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
+			return pos;
+
+		pos = PCI_EXT_CAP_NEXT(header);
+		if (pos < PCI_CFG_SPACE_SIZE)
+			break;
+
+		header = dw_pcie_readl_dbi(pci, pos);
+	}
+
+	return 0;
+}
+
+int dw_pcie_find_ext_capability(struct dw_pcie *pci, int cap)
+{
+	return dw_pcie_find_next_ext_capability(pci, 0, cap);
+}
+EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
+
  int dw_pcie_read(void __iomem *addr, int size, u32 *val)
  {
  	if (!IS_ALIGNED((uintptr_t)addr, size)) {
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 35160b4ce929..67307842e003 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -249,6 +249,7 @@ struct dw_pcie {
  		container_of((endpoint), struct dw_pcie, ep)
u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
+int dw_pcie_find_ext_capability(struct dw_pcie *pci, int cap);
int dw_pcie_read(void __iomem *addr, int size, u32 *val);
  int dw_pcie_write(void __iomem *addr, int size, u32 val);
--
2.17.1





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