+
+ /*
+ * RICOH 0xe823 SD/MMC card reader fails to recognize
+ * certain types of SD/MMC cards. Lowering the SD base
+ * clock frequency from 200Mhz to 50Mhz fixes this issue.
+ *
+ * 0x150 - SD2.0 mode enable for changing base clock
+ * frequency to 50Mhz
+ * 0xe1 - Base clock frequency
+ * 0x32 - 50Mhz new clock frequency
+ * 0xf9 - Key register for 0x150
+ * 0xfc - key register for 0xe1
+ */
+ if (dev->device == PCI_DEVICE_ID_RICOH_R5CE823) {
+ pci_write_config_byte(dev, 0xf9, 0xfc);
+ pci_write_config_byte(dev, 0x150, 0x10);
+ pci_write_config_byte(dev, 0xf9, 0x00);
+ pci_write_config_byte(dev, 0xfc, 0x01);
+ pci_write_config_byte(dev, 0xe1, 0x32);
+ pci_write_config_byte(dev, 0xfc, 0x00);
+
+ dev_notice(&dev->dev, "MMC controller base frequency changed to 50Mhz.\n");
+ }