[RFC 06/47] mtd: nand: stm_nand_bch: change between BCH and Hamming modes

[Lee Jones]

The EMISS is a device which, amongst other things, controls various
flash memory modes. We make use of it here merely to flip the
HAMMING_NOT_BCH bit dependant on whether we wish to operate in Hamming
or BCH modes. The STM BCH driver makes good use of the helper introduced
here.

Signed-off-by: Lee Jones <lee.jones at linaro.org>
---
 include/linux/mtd/stm_nand.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/include/linux/mtd/stm_nand.h b/include/linux/mtd/stm_nand.h
index 9210d5c..da2006c 100644
--- a/include/linux/mtd/stm_nand.h
+++ b/include/linux/mtd/stm_nand.h
@@ -15,6 +15,8 @@
 #ifndef __LINUX_STM_NAND_H
 #define __LINUX_STM_NAND_H
 
+#include <linux/io.h>
+
 struct stm_plat_nand_bch_data {
 	struct stm_nand_bank_data *bank;
 	enum stm_nand_bch_ecc_config bch_ecc_cfg;
@@ -30,4 +32,44 @@ struct stm_plat_nand_bch_data {
 	bool flashss;
 };
 
+#define EMISS_BASE				0xfef01000
+#define EMISS_CONFIG				0x0000
+#define EMISS_CONFIG_HAMMING_NOT_BCH		(0x1 << 6)
+
+enum nandi_controllers {
+	STM_NANDI_UNCONFIGURED,
+	STM_NANDI_HAMMING,
+	STM_NANDI_BCH
+};
+
+static inline void emiss_nandi_select(enum nandi_controllers controller)
+{
+	unsigned v;
+	void __iomem *emiss_config_base;
+
+	emiss_config_base = ioremap(EMISS_BASE, 4);
+	if (!emiss_config_base) {
+		pr_err("%s: failed to ioremap EMISS\n", __func__);
+		return;
+	}
+
+	v = readl(emiss_config_base + EMISS_CONFIG);
+
+	if (controller == STM_NANDI_HAMMING) {
+		if (v & EMISS_CONFIG_HAMMING_NOT_BCH)
+			goto out;
+		v |= EMISS_CONFIG_HAMMING_NOT_BCH;
+	} else {
+		if (!(v & EMISS_CONFIG_HAMMING_NOT_BCH))
+			goto out;
+		v &= ~EMISS_CONFIG_HAMMING_NOT_BCH;
+	}
+
+	writel(v, emiss_config_base + EMISS_CONFIG);
+	readl(emiss_config_base + EMISS_CONFIG);
+
+out:
+	iounmap(emiss_config_base);
+}
+
 #endif /* __LINUX_STM_NAND_H */
-- 
1.8.3.2