arm: mvebu: a38x: serdes: Don't overwrite read-only SAR PCIe registers

Device/Port Type bits of PCIe Root Port PCI Express Capabilities Register
are read-only SAR registers and are initialized according to current mode
configured by PCIe controller. Changing PCIe controller mode (from Root
Complex mode to Endpoint mode or the other way) is possible via PCI
Express Control Register (offset 0x41A00), bit 1 (ConfRoot Complex). This
has to be done in PCIe controller driver (in our case pci_mvebu.c). Note
that default mode is Root Complex.

Maximum Link Speed bits of PCIe Root Port Link Capabilities Register are
platform specific and overwriting them does not make sense. They are set by
PCIe controller according to current SerDes configuration. For A38x it is
5.0 GT/s if SerDes supports appropriate speed.

Maximum Link Width bits of PCIe Root Port Link Capabilities Register are
read-only SAR registers, but unfortunately if this is not set correctly
here, then access PCI config space of the endpoint card behind this Root
Port does not work.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>

3 files changed, 19 insertions, 47 deletions

diff --git a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
index 0eb31d589ca..7c18df8113a 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
+++ b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
@@ -28,28 +28,6 @@ int hws_pex_config(const struct serdes_map *serdes_map, u8 count)
 
 	DEBUG_INIT_FULL_S("\n### hws_pex_config ###\n");
 
-	for (idx = 0; idx < count; idx++) {
-		serdes_type = serdes_map[idx].serdes_type;
-		/* configuration for PEX only */
-		if ((serdes_type != PEX0) && (serdes_type != PEX1) &&
-		    (serdes_type != PEX2) && (serdes_type != PEX3))
-			continue;
-
-		if ((serdes_type != PEX0) &&
-		    ((serdes_map[idx].serdes_mode == PEX_ROOT_COMPLEX_X4) ||
-		     (serdes_map[idx].serdes_mode == PEX_END_POINT_X4))) {
-			/* for PEX by4 - relevant for the first port only */
-			continue;
-		}
-
-		/* Set Device/Port Type to RootComplex */
-		pex_idx = serdes_type - PEX0;
-		tmp = reg_read(PEX_CAPABILITIES_REG(pex_idx));
-		tmp &= ~(0xf << 20);
-		tmp |= (0x4 << 20);
-		reg_write(PEX_CAPABILITIES_REG(pex_idx), tmp);
-	}
-
 	tmp = reg_read(SOC_CONTROL_REG1);
 	tmp &= ~0x03;
 
diff --git a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.h b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.h
index a882d242083..5d70166fc5b 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.h
+++ b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.h
@@ -6,8 +6,12 @@
 #ifndef _CTRL_PEX_H
 #define _CTRL_PEX_H
 
+#include <pci.h>
 #include "high_speed_env_spec.h"
 
+/* Direct access to PEX0 Root Port's PCIe Capability structure */
+#define PEX0_RP_PCIE_CFG_OFFSET		(0x00080000 + 0x60)
+
 /* Sample at Reset */
 #define MPP_SAMPLE_AT_RESET(id)		(0xe4200 + (id * 4))
 
diff --git a/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c b/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
index 7b4710501df..c089479a9b8 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
+++ b/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
@@ -1712,7 +1712,7 @@ int serdes_power_up_ctrl(u32 serdes_num, int serdes_power_up,
 				(serdes_mode == PEX_END_POINT_X1);
 			pex_idx = serdes_type - PEX0;
 
-			if ((is_pex_by1 == 1) || (serdes_type == PEX0)) {
+			if (serdes_type == PEX0) {
 				/* For PEX by 4, init only the PEX 0 */
 				reg_data = reg_read(SOC_CONTROL_REG1);
 				if (is_pex_by1 == 1)
@@ -1721,30 +1721,20 @@ int serdes_power_up_ctrl(u32 serdes_num, int serdes_power_up,
 					reg_data &= ~0x4000;
 				reg_write(SOC_CONTROL_REG1, reg_data);
 
-				/* Set Maximum Link Width to X1 or X4 */
-				reg_data = reg_read(PEX_CFG_DIRECT_ACCESS(
-						     pex_idx,
-						     PEX_LINK_CAPABILITY_REG));
-				reg_data &= ~0x3f0;
-				if (is_pex_by1 == 1)
-					reg_data |= 0x10;
-				else
-					reg_data |= 0x40;
-				reg_write(PEX_CFG_DIRECT_ACCESS(
-					   pex_idx,
-					   PEX_LINK_CAPABILITY_REG),
-					  reg_data);
-
-				/* Set Maximum Link Speed to 5 GT/s */
-				reg_data = reg_read(PEX_CFG_DIRECT_ACCESS(
-						     pex_idx,
-						     PEX_LINK_CAPABILITY_REG));
-				reg_data &= ~0xf;
-				reg_data |= 0x2;
-				reg_write(PEX_CFG_DIRECT_ACCESS(
-					   pex_idx,
-					   PEX_LINK_CAPABILITY_REG),
-					  reg_data);
+				/*
+				 * Set Maximum Link Width to X1 or X4 in Root
+				 * Port's PCIe Link Capability register.
+				 * This register is read-only but if is not set
+				 * correctly then access to PCI config space of
+				 * endpoint card behind this Root Port does not
+				 * work.
+				 */
+				reg_data = reg_read(PEX0_RP_PCIE_CFG_OFFSET +
+						    PCI_EXP_LNKCAP);
+				reg_data &= ~PCI_EXP_LNKCAP_MLW;
+				reg_data |= (is_pex_by1 ? 1 : 4) << 4;
+				reg_write(PEX0_RP_PCIE_CFG_OFFSET +
+					  PCI_EXP_LNKCAP, reg_data);
 
 				/*
 				 * Set Common Clock Configuration to indicates