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[PATCH v5 1/5] PCI: designware: ensure ATU is enabled before IO/conf space accesses

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  [PATCH v5 1/5] PCI: designware: ensure ATU is enabled before IO/conf space accesses Stanimir Varbanov <stanimir.varbanov@linaro.org> - 2015-12-18 13:40 +0100
    Re: [PATCH v5 1/5] PCI: designware: ensure ATU is enabled before  IO/conf space accesses Pratyush Anand <pratyush.anand@gmail.com> - 2015-12-18 15:50 +0100

#1294749 — [PATCH v5 1/5] PCI: designware: ensure ATU is enabled before IO/conf space accesses

There is no guarantees that enabling ATU will hit the hardware
immediately, and subsequent accesses to configuration / IO spaces
are reliable. So fixing this by read back PCIE_ATU_CR2 register
just after writing.

Without such a fix the PCI device enumeration during kernel boot
is not reliable, and reading configuration space for particular
PCI device on the bus returns zero aka no device.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
---
 drivers/pci/host/pcie-designware.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c
index 02a7452bdf23..7880de63895d 100644
--- a/drivers/pci/host/pcie-designware.c
+++ b/drivers/pci/host/pcie-designware.c
@@ -154,6 +154,8 @@ static int dw_pcie_wr_own_conf(struct pcie_port *pp, int where, int size,
 static void dw_pcie_prog_outbound_atu(struct pcie_port *pp, int index,
 		int type, u64 cpu_addr, u64 pci_addr, u32 size)
 {
+	u32 val;
+
 	dw_pcie_writel_rc(pp, PCIE_ATU_REGION_OUTBOUND | index,
 			  PCIE_ATU_VIEWPORT);
 	dw_pcie_writel_rc(pp, lower_32_bits(cpu_addr), PCIE_ATU_LOWER_BASE);
@@ -164,6 +166,11 @@ static void dw_pcie_prog_outbound_atu(struct pcie_port *pp, int index,
 	dw_pcie_writel_rc(pp, upper_32_bits(pci_addr), PCIE_ATU_UPPER_TARGET);
 	dw_pcie_writel_rc(pp, type, PCIE_ATU_CR1);
 	dw_pcie_writel_rc(pp, PCIE_ATU_ENABLE, PCIE_ATU_CR2);
+	/*
+	 * ensure that the ATU enable has been happaned before accessing
+	 * pci configuration/io spaces through dw_pcie_cfg_[read|write].
+	 */
+	dw_pcie_readl_rc(pp, PCIE_ATU_CR2, &val);
 }
 
 static struct irq_chip dw_msi_irq_chip = {
-- 
1.7.9.5

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#1294922 — Re: [PATCH v5 1/5] PCI: designware: ensure ATU is enabled before IO/conf space accesses

On Fri, Dec 18, 2015 at 6:08 PM, Stanimir Varbanov
<stanimir.varbanov@linaro.org> wrote:
> There is no guarantees that enabling ATU will hit the hardware
> immediately, and subsequent accesses to configuration / IO spaces
> are reliable. So fixing this by read back PCIE_ATU_CR2 register
> just after writing.
>
> Without such a fix the PCI device enumeration during kernel boot
> is not reliable, and reading configuration space for particular
> PCI device on the bus returns zero aka no device.
>
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>

Acked-by: Pratyush Anand <pratyush.anand@gmail.com>
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