[PATCH v2 05/65] PCI: designware: Use exact access size in dw_pcie_cfg_read()

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Port of a Linux commit c003ca99632e1783466f459033874a0e1e31457b

  dw_pcie_cfg_write() uses the exact 8-, 16-, or 32-bit access size
  requested, but dw_pcie_cfg_read() previously performed a 32-bit read and
  masked out the bits requested.

  Use the exact access size in dw_pcie_cfg_read().  For example, if we want
  an 8-bit read, use readb() instead of using readl() and masking out the 8
  bits we need.  This makes it symmetric with dw_pcie_cfg_write().

  [bhelgaas: split into separate patch, set *val = 0 in failure case]
  Signed-off-by: Gabriele Paoloni <gabriele.paoloni@xxxxxxxxxx>
  Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

NOTE: Original Linux commit incorrectly handles the case of single
byte read by doing

       else if (size == 1)
               *val = readb(addr + (where & 1));

instead of

       else if (size == 1)
               *val = readb(addr + (where & 3));

which would be symmetric with what's done in dw_pcie_cfg_write(). This
was most likely overlooked since commit that follow change the
signature of the function, remove 'where' as argument completely,
inadvertenly fixing the problem.

Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
---
 drivers/pci/pcie-designware.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie-designware.c b/drivers/pci/pcie-designware.c
index 547d402a7..bda85c30e 100644
--- a/drivers/pci/pcie-designware.c
+++ b/drivers/pci/pcie-designware.c
@@ -76,14 +76,16 @@ static unsigned long global_io_offset;
 
 int dw_pcie_cfg_read(void __iomem *addr, int where, int size, u32 *val)
 {
-	*val = readl(addr);
-
-	if (size == 1)
-		*val = (*val >> (8 * (where & 3))) & 0xff;
+	if (size == 4)
+		*val = readl(addr);
 	else if (size == 2)
-		*val = (*val >> (8 * (where & 3))) & 0xffff;
-	else if (size != 4)
+		*val = readw(addr + (where & 2));
+	else if (size == 1)
+		*val = readb(addr + (where & 3));
+	else {
+		*val = 0;
 		return PCIBIOS_BAD_REGISTER_NUMBER;
+	}
 
 	return PCIBIOS_SUCCESSFUL;
 }
-- 
2.19.1


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