PCI: aardvark: Fix checking for PIO status

There is an issue that when PCIe switch is connected to an Armada 3700
board, there will be lots of warnings about PIO errors when reading the
config space. According to Aardvark PIO read and write sequence in HW
specification, the current way to check PIO status has the following
issues:

1) For PIO read operation, it reports the error message, which should be
   avoided according to HW specification.

2) For PIO read and write operations, it only checks PIO operation complete
   status, which is not enough, and error status should also be checked.

This patch aligns the code with Aardvark PIO read and write sequence in HW
specification on PIO status check and fix the warnings when reading config
space.

[pali: Fix CRS handling when CRSSVE is not enabled]

Link: https://lore.kernel.org/r/20210722144041.12661-2-pali@kernel.org


Tested-by: Victor Gu <xigu@marvell.com>
Signed-off-by: Evan Wang <xswang@marvell.com>
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Victor Gu <xigu@marvell.com>
Reviewed-by: Marek Behún <kabel@kernel.org>
Cc: stable@vger.kernel.org # b1bd5714 ("PCI: aardvark: Indicate error in 'val' when config read fails")

drivers/pci/controller/pci-aardvark.c

@@ -58,6 +58,7 @@
 #define   PIO_COMPLETION_STATUS_CRS		2
 #define   PIO_COMPLETION_STATUS_CA		4
 #define   PIO_NON_POSTED_REQ			BIT(10)
+#define   PIO_ERR_STATUS			BIT(11)
 #define PIO_ADDR_LS				(PIO_BASE_ADDR + 0x8)
 #define PIO_ADDR_MS				(PIO_BASE_ADDR + 0xc)
 #define PIO_WR_DATA				(PIO_BASE_ADDR + 0x10)
@@ -472,7 +473,7 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
 	advk_writel(pcie, reg, PCIE_CORE_CMD_STATUS_REG);
 }
 
-static void advk_pcie_check_pio_status(struct advk_pcie *pcie)
+static int advk_pcie_check_pio_status(struct advk_pcie *pcie, u32 *val)
 {
 	struct device *dev = &pcie->pdev->dev;
 	u32 reg;
@@ -483,14 +484,49 @@ static void advk_pcie_check_pio_status(struct advk_pcie *pcie)
 	status = (reg & PIO_COMPLETION_STATUS_MASK) >>
 		PIO_COMPLETION_STATUS_SHIFT;
 
-	if (!status)
-		return;
-
+	/*
+	 * According to HW spec, the PIO status check sequence as below:
+	 * 1) even if COMPLETION_STATUS(bit9:7) indicates successful,
+	 *    it still needs to check Error Status(bit11), only when this bit
+	 *    indicates no error happen, the operation is successful.
+	 * 2) value Unsupported Request(1) of COMPLETION_STATUS(bit9:7) only
+	 *    means a PIO write error, and for PIO read it is successful with
+	 *    a read value of 0xFFFFFFFF.
+	 * 3) value Completion Retry Status(CRS) of COMPLETION_STATUS(bit9:7)
+	 *    only means a PIO write error, and for PIO read it is successful
+	 *    with a read value of 0xFFFF0001.
+	 * 4) value Completer Abort (CA) of COMPLETION_STATUS(bit9:7) means
+	 *    error for both PIO read and PIO write operation.
+	 * 5) other errors are indicated as 'unknown'.
+	 */
 	switch (status) {
+	case PIO_COMPLETION_STATUS_OK:
+		if (reg & PIO_ERR_STATUS) {
+			strcomp_status = "COMP_ERR";
+			break;
+		}
+		/* Get the read result */
+		if (val)
+			*val = advk_readl(pcie, PIO_RD_DATA);
+		/* No error */
+		strcomp_status = NULL;
+		break;
 	case PIO_COMPLETION_STATUS_UR:
 		strcomp_status = "UR";
 		break;
 	case PIO_COMPLETION_STATUS_CRS:
+		/* PCIe r4.0, sec 2.3.2, says:
+		 * If CRS Software Visibility is not enabled, the Root Complex
+		 * must re-issue the Configuration Request as a new Request.
+		 * A Root Complex implementation may choose to limit the number
+		 * of Configuration Request/CRS Completion Status loops before
+		 * determining that something is wrong with the target of the
+		 * Request and taking appropriate action, e.g., complete the
+		 * Request to the host as a failed transaction.
+		 *
+		 * To simplify implementation do not re-issue the Configuration
+		 * Request and complete the Request as a failed transaction.
+		 */
 		strcomp_status = "CRS";
 		break;
 	case PIO_COMPLETION_STATUS_CA:
@@ -501,6 +537,9 @@ static void advk_pcie_check_pio_status(struct advk_pcie *pcie)
 		break;
 	}
 
+	if (!strcomp_status)
+		return 0;
+
 	if (reg & PIO_NON_POSTED_REQ)
 		str_posted = "Non-posted";
 	else
@@ -508,6 +547,8 @@ static void advk_pcie_check_pio_status(struct advk_pcie *pcie)
 
 	dev_err(dev, "%s PIO Response Status: %s, %#x @ %#x\n",
 		str_posted, strcomp_status, reg, advk_readl(pcie, PIO_ADDR_LS));
+
+	return -EFAULT;
 }
 
 static int advk_pcie_wait_pio(struct advk_pcie *pcie)
@@ -745,10 +786,13 @@ static int advk_pcie_rd_conf(struct pci_bus *bus, u32 devfn,
 		return PCIBIOS_SET_FAILED;
 	}
 
-	advk_pcie_check_pio_status(pcie);
+	/* Check PIO status and get the read result */
+	ret = advk_pcie_check_pio_status(pcie, val);
+	if (ret < 0) {
+		*val = 0xffffffff;
+		return PCIBIOS_SET_FAILED;
+	}
 
-	/* Get the read result */
-	*val = advk_readl(pcie, PIO_RD_DATA);
 	if (size == 1)
 		*val = (*val >> (8 * (where & 3))) & 0xff;
 	else if (size == 2)
@@ -812,7 +856,9 @@ static int advk_pcie_wr_conf(struct pci_bus *bus, u32 devfn,
 	if (ret < 0)
 		return PCIBIOS_SET_FAILED;
 
-	advk_pcie_check_pio_status(pcie);
+	ret = advk_pcie_check_pio_status(pcie, NULL);
+	if (ret < 0)
+		return PCIBIOS_SET_FAILED;
 
 	return PCIBIOS_SUCCESSFUL;
 }