mb/siemens/mc_apl2: Limit SD-Card speed to DDR50
Due to PCB limitations the SD-Card interface is not able to operate
with the highest frequency reliably. The OS driver will switch to
the highest mode if a SD-Card is attached which supports this high
frequency mode. In order to work around this PCB limitation disable the
high frequency modes in the controller capabilities (SDR104 and HS400
mode) and leave SDR50 and DDR50 enabled.
Change-Id: Ia5fed5fb70b027de34170b49620927614a00fb7a
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32542
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
diff --git a/src/mainboard/siemens/mc_apl1/variants/mc_apl2/mainboard.c b/src/mainboard/siemens/mc_apl1/variants/mc_apl2/mainboard.c
index 0c2418a..f52091b 100644
--- a/src/mainboard/siemens/mc_apl1/variants/mc_apl2/mainboard.c
+++ b/src/mainboard/siemens/mc_apl1/variants/mc_apl2/mainboard.c
@@ -23,6 +23,11 @@
#include <timer.h>
#include <timestamp.h>
#include <baseboard/variants.h>
+#include <soc/pci_devs.h>
+
+#define SD_CAP_BYP 0x810
+#define SD_CAP_BYP_EN 0x5A
+#define SD_CAP_BYP_REG1 0x814
void variant_mainboard_final(void)
{
@@ -36,6 +41,21 @@
cmd |= PCI_COMMAND_MASTER;
pci_write_config16(dev, PCI_COMMAND, cmd);
}
+
+ /* Reduce SD-Card speed to DDR50 because of PCB constraints. */
+ dev = pcidev_path_on_root(PCH_DEVFN_SDCARD);
+ if (dev) {
+ uint32_t reg;
+ struct resource *res = find_resource(dev, PCI_BASE_ADDRESS_0);
+ if (!res)
+ return;
+
+ write32(res2mmio(res, SD_CAP_BYP, 0), SD_CAP_BYP_EN);
+ reg = read32(res2mmio(res, SD_CAP_BYP_REG1, 0));
+ /* Disable HS400 and SDR104, keep SDR50 and DDR50 modes. */
+ reg &= ~0x20005800;
+ write32(res2mmio(res, SD_CAP_BYP_REG1, 0), reg);
+ }
}
static void wait_for_legacy_dev(void *unused)