[PATCH 5.15 150/917] PCI: aardvark: Fix support for bus mastering and PCI_COMMAND on emulated bridge

Greg Kroah-Hartman
2021-11-15T23:31:21Z

From: Pali Rohár <pali@kernel.org>

commit 771153fc884f566a89af2d30033b7f3bc6e24e84 upstream.

>From very vague, ambiguous and incomplete information from Marvell we
deduced that the 32-bit Aardvark register at address 0x4
(PCIE_CORE_CMD_STATUS_REG), which is not documented for Root Complex mode
in the Functional Specification (only for Endpoint mode), controls two
16-bit PCIe registers: Command Register and Status Registers of PCIe Root
Port.

This means that bit 2 controls bus mastering and forwarding of memory and
I/O requests in the upstream direction. According to PCI specifications
bits [0:2] of Command Register, this should be by default disabled on
reset. So explicitly disable these bits at early setup of the Aardvark
driver.

Remove code which unconditionally enables all 3 bits and let kernel code
(via pci_set_master() function) to handle bus mastering of Root PCIe
Bridge via emulated PCI_COMMAND on emulated bridge.

Link: https://lore.kernel.org/r/20211028185659.20329-5-kabel@kernel.org
Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI bridge config space")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org # b2a56469d550 ("PCI: aardvark: Add FIXME comment for PCIE_CORE_CMD_STATUS_REG access")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/pci/controller/pci-aardvark.c | 54 +++++++++++++++++++++++-----------
1 file changed, 38 insertions(+), 16 deletions(-)

--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -31,9 +31,6 @@
/* PCIe core registers */
#define PCIE_CORE_DEV_ID_REG 0x0
#define PCIE_CORE_CMD_STATUS_REG 0x4
-#define PCIE_CORE_CMD_IO_ACCESS_EN BIT(0)
-#define PCIE_CORE_CMD_MEM_ACCESS_EN BIT(1)
-#define PCIE_CORE_CMD_MEM_IO_REQ_EN BIT(2)
#define PCIE_CORE_DEV_REV_REG 0x8
#define PCIE_CORE_PCIEXP_CAP 0xc0
#define PCIE_CORE_ERR_CAPCTL_REG 0x118
@@ -563,6 +560,11 @@ static void advk_pcie_setup_hw(struct ad
reg = (PCI_VENDOR_ID_MARVELL << 16) | PCI_VENDOR_ID_MARVELL;
advk_writel(pcie, reg, VENDOR_ID_REG);

+ /* Disable Root Bridge I/O space, memory space and bus mastering */
+ reg = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
+ reg &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
+ advk_writel(pcie, reg, PCIE_CORE_CMD_STATUS_REG);
+
/* Set Advanced Error Capabilities and Control PF0 register */
reg = PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX |
PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX_EN |
@@ -660,19 +662,6 @@ static void advk_pcie_setup_hw(struct ad
advk_pcie_disable_ob_win(pcie, i);

advk_pcie_train_link(pcie);
-
- /*
- * FIXME: The following register update is suspicious. This register is
- * applicable only when the PCI controller is configured for Endpoint
- * mode, not as a Root Complex. But apparently when this code is
- * removed, some cards stop working. This should be investigated and
- * a comment explaining this should be put here.
- */
- reg = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
- reg |= PCIE_CORE_CMD_MEM_ACCESS_EN |
- PCIE_CORE_CMD_IO_ACCESS_EN |
- PCIE_CORE_CMD_MEM_IO_REQ_EN;
- advk_writel(pcie, reg, PCIE_CORE_CMD_STATUS_REG);
}

static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u32 *val)
@@ -793,6 +782,37 @@ static int advk_pcie_wait_pio(struct adv
return -ETIMEDOUT;
}

+static pci_bridge_emul_read_status_t
+advk_pci_bridge_emul_base_conf_read(struct pci_bridge_emul *bridge,
+ int reg, u32 *value)
+{
+ struct advk_pcie *pcie = bridge->data;
+
+ switch (reg) {
+ case PCI_COMMAND:
+ *value = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
+ return PCI_BRIDGE_EMUL_HANDLED;
+
+ default:
+ return PCI_BRIDGE_EMUL_NOT_HANDLED;
+ }
+}
+
+static void
+advk_pci_bridge_emul_base_conf_write(struct pci_bridge_emul *bridge,
+ int reg, u32 old, u32 new, u32 mask)
+{
+ struct advk_pcie *pcie = bridge->data;
+
+ switch (reg) {
+ case PCI_COMMAND:
+ advk_writel(pcie, new, PCIE_CORE_CMD_STATUS_REG);
+ break;
+
+ default:
+ break;
+ }
+}

static pci_bridge_emul_read_status_t
advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
@@ -893,6 +913,8 @@ advk_pci_bridge_emul_pcie_conf_write(str
}

static struct pci_bridge_emul_ops advk_pci_bridge_emul_ops = {
+ .read_base = advk_pci_bridge_emul_base_conf_read,
+ .write_base = advk_pci_bridge_emul_base_conf_write,
.read_pcie = advk_pci_bridge_emul_pcie_conf_read,
.write_pcie = advk_pci_bridge_emul_pcie_conf_write,
};