ath79: add Mikrotik rb4xx series drivers

This adds 3 Mikrotik rb4xx series drivers as follows:

rb4xx-cpld: This is in the mfd subsystem, and is the parent CPLD device
that interfaces between the SoC SPI bus and its two children below.
rb4xx-gpio: This is the GPIO expander.
rb4xx-nand: This is the NAND driver.

The history of this code comes in three phases.

1. The first is a May 2015 attempt to push the equivalient ar71xx rb4xx
drivers upstream. See https://lore.kernel.org/patchwork/patch/940880/.

Module-author: Gabor Juhos <juhosg@openwrt.org>
Module-author: Imre Kaloz <kaloz@openwrt.org>
Module-author: Bert Vermeulen <bert@biot.com>

2. Next several ar71xx patches were applied bringing the code current.

commit 7bbf4117c6fe4b764d9d7c62fb2bcf6dd93bff2c
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

commit af79fdbe4af32a287798b579141204bda056b8aa
commit 889272d92db689fd9c910243635e44c9d8323095
commit e21cb649a235180563363b8af5ba8296b9ac0baa
commit 7c09fa4a7492ca436f2c94bd9a465b7c5bbeed6f
Signed-off-by: Felix Fietkau <nbd@nbd.name>

3. Finally a heavy refactor to split the driver into the three new
subsystems, and updated to work with the device tree configuration, plus
updates and review feedback incorporated

Reviewed-by: Thibaut VARÈNE <hacks@slashdirt.org>
Signed-off-by: Christopher Hill <ch6574@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/target/linux/ath79/files/include/mfd/rb4xx-cpld.h b/target/linux/ath79/files/include/mfd/rb4xx-cpld.h
new file mode 100644
index 0000000000..d73617bfb1
--- /dev/null
+++ b/target/linux/ath79/files/include/mfd/rb4xx-cpld.h
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CPLD driver for the MikroTik RouterBoard 4xx series
+ *
+ * Copyright (C) 2008-2011 Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
+ * Copyright (C) 2015 Bert Vermeulen <bert@biot.com>
+ * Copyright (C) 2020 Christopher Hill <ch6574@gmail.com>
+ *
+ * This file was based on the driver for Linux 2.6.22 published by
+ * MikroTik for their RouterBoard 4xx series devices.
+ */
+#include <linux/spi/spi.h>
+
+struct rb4xx_cpld {
+	struct spi_device *spi;
+
+	int (*write_nand)(struct rb4xx_cpld *self, const void *tx_buf,
+			  unsigned int len);
+	int (*read_nand)(struct rb4xx_cpld *self, void *rx_buf,
+			 unsigned int len);
+
+	int (*gpio_set_0_7)(struct rb4xx_cpld *self, u8 values);
+	int (*gpio_set_8)(struct rb4xx_cpld *self, u8 value);
+};