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From 61cba34bd6c1bddfc38f94cc3f80bdfefcc3393b Mon Sep 17 00:00:00 2001
From: Ricardo Ribalda <ricardo.ribalda@gmail.com>
Date: Fri, 2 Dec 2016 12:31:44 +0100
Subject: [PATCH] mtd: spi-nor: Add support for S3AN spi-nor devices

Xilinx Spartan-3AN FPGAs contain an In-System Flash where they keep
their configuration data and (optionally) some user data.

The protocol of this flash follows most of the spi-nor standard. With
the following differences:

- Page size might not be a power of two.
- The address calculation (default addressing mode).
- The spi nor commands used.

Protocol is described on Xilinx User Guide UG333

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 154 ++++++++++++++++++++++++++++++++++++++++--
 include/linux/mtd/spi-nor.h   |  12 ++++
 2 files changed, 161 insertions(+), 5 deletions(-)

--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -75,6 +75,12 @@ struct flash_info {
                                         * bit. Must be used with
                                         * SPI_NOR_HAS_LOCK.
                                         */
+#define        SPI_S3AN                BIT(10) /*
+                                        * Xilinx Spartan 3AN In-System Flash
+                                        * (MFR cannot be used for probing
+                                        * because it has the same value as
+                                        * ATMEL flashes)
+                                       */
 };
 
 #define JEDEC_MFR(info)        ((info)->id[0])
@@ -217,6 +223,21 @@ static inline int set_4byte(struct spi_n
                return nor->write_reg(nor, SPINOR_OP_BRWR, nor->cmd_buf, 1);
        }
 }
+
+static int s3an_sr_ready(struct spi_nor *nor)
+{
+       int ret;
+       u8 val;
+
+       ret = nor->read_reg(nor, SPINOR_OP_XRDSR, &val, 1);
+       if (ret < 0) {
+               dev_err(nor->dev, "error %d reading XRDSR\n", (int) ret);
+               return ret;
+       }
+
+       return !!(val & XSR_RDY);
+}
+
 static inline int spi_nor_sr_ready(struct spi_nor *nor)
 {
        int sr = read_sr(nor);
@@ -238,7 +259,11 @@ static inline int spi_nor_fsr_ready(stru
 static int spi_nor_ready(struct spi_nor *nor)
 {
        int sr, fsr;
-       sr = spi_nor_sr_ready(nor);
+
+       if (nor->flags & SNOR_F_READY_XSR_RDY)
+               sr = s3an_sr_ready(nor);
+       else
+               sr = spi_nor_sr_ready(nor);
        if (sr < 0)
                return sr;
        fsr = nor->flags & SNOR_F_USE_FSR ? spi_nor_fsr_ready(nor) : 1;
@@ -320,6 +345,24 @@ static void spi_nor_unlock_and_unprep(st
 }
 
 /*
+ * This code converts an address to the Default Address Mode, that has non
+ * power of two page sizes. We must support this mode because it is the default
+ * mode supported by Xilinx tools, it can access the whole flash area and
+ * changing over to the Power-of-two mode is irreversible and corrupts the
+ * original data.
+ * Addr can safely be unsigned int, the biggest S3AN device is smaller than
+ * 4 MiB.
+ */
+static loff_t spi_nor_s3an_addr_convert(struct spi_nor *nor, unsigned int addr)
+{
+       unsigned int offset = addr;
+
+       offset %= nor->page_size;
+
+       return ((addr - offset) << 1) | offset;
+}
+
+/*
  * Initiate the erasure of a single sector
  */
 static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
@@ -327,6 +370,9 @@ static int spi_nor_erase_sector(struct s
        u8 buf[SPI_NOR_MAX_ADDR_WIDTH];
        int i;
 
+       if (nor->flags & SNOR_F_S3AN_ADDR_DEFAULT)
+               addr = spi_nor_s3an_addr_convert(nor, addr);
+
        if (nor->erase)
                return nor->erase(nor, addr);
 
@@ -368,7 +414,7 @@ static int spi_nor_erase(struct mtd_info
                return ret;
 
        /* whole-chip erase? */
-       if (len == mtd->size) {
+       if (len == mtd->size && !(nor->flags & SNOR_F_NO_OP_CHIP_ERASE)) {
                unsigned long timeout;
 
                write_enable(nor);
@@ -782,6 +828,19 @@ static int spi_nor_is_locked(struct mtd_
                .addr_width = (_addr_width),                            \
                .flags = (_flags),
 
+#define S3AN_INFO(_jedec_id, _n_sectors, _page_size)                   \
+               .id = {                                                 \
+                       ((_jedec_id) >> 16) & 0xff,                     \
+                       ((_jedec_id) >> 8) & 0xff,                      \
+                       (_jedec_id) & 0xff                              \
+                       },                                              \
+               .id_len = 3,                                            \
+               .sector_size = (8*_page_size),                          \
+               .n_sectors = (_n_sectors),                              \
+               .page_size = _page_size,                                \
+               .addr_width = 3,                                        \
+               .flags = SPI_NOR_NO_FR | SPI_S3AN,
+
 /* NOTE: double check command sets and memory organization when you add
  * more nor chips.  This current list focusses on newer chips, which
  * have been converging on command sets which including JEDEC ID.
@@ -1020,6 +1079,13 @@ static const struct flash_info spi_nor_i
        { "cat25c09", CAT25_INFO( 128, 8, 32, 2, SPI_NOR_NO_ERASE | SPI_NOR_NO_FR) },
        { "cat25c17", CAT25_INFO( 256, 8, 32, 2, SPI_NOR_NO_ERASE | SPI_NOR_NO_FR) },
        { "cat25128", CAT25_INFO(2048, 8, 64, 2, SPI_NOR_NO_ERASE | SPI_NOR_NO_FR) },
+
+       /* Xilinx S3AN Internal Flash */
+       { "3S50AN", S3AN_INFO(0x1f2200, 64, 264) },
+       { "3S200AN", S3AN_INFO(0x1f2400, 256, 264) },
+       { "3S400AN", S3AN_INFO(0x1f2400, 256, 264) },
+       { "3S700AN", S3AN_INFO(0x1f2500, 512, 264) },
+       { "3S1400AN", S3AN_INFO(0x1f2600, 512, 528) },
        { },
 };
 
@@ -1060,7 +1126,12 @@ static int spi_nor_read(struct mtd_info
                return ret;
 
        while (len) {
-               ret = nor->read(nor, from, len, buf);
+               loff_t addr = from;
+
+               if (nor->flags & SNOR_F_S3AN_ADDR_DEFAULT)
+                       addr = spi_nor_s3an_addr_convert(nor, addr);
+
+               ret = nor->read(nor, addr, len, buf);
                if (ret == 0) {
                        /* We shouldn't see 0-length reads */
                        ret = -EIO;
@@ -1181,8 +1252,23 @@ static int spi_nor_write(struct mtd_info
 
        for (i = 0; i < len; ) {
                ssize_t written;
+               loff_t addr = to + i;
 
-               page_offset = (to + i) & (nor->page_size - 1);
+               /*
+                * If page_size is a power of two, the offset can be quickly
+                * calculated with an AND operation. On the other cases we
+                * need to do a modulus operation (more expensive).
+                * Power of two numbers have only one bit set and we can use
+                * the instruction hweight32 to detect if we need to do a
+                * modulus (do_div()) or not.
+                */
+               if (hweight32(nor->page_size) == 1) {
+                       page_offset = addr & (nor->page_size - 1);
+               } else {
+                       uint64_t aux = addr;
+
+                       page_offset = do_div(aux, nor->page_size);
+               }
                WARN_ONCE(page_offset,
                          "Writing at offset %zu into a NOR page. Writing partial pages may decrease reliability and increase wear of NOR flash.",
                          page_offset);
@@ -1190,8 +1276,11 @@ static int spi_nor_write(struct mtd_info
                page_remain = min_t(size_t,
                                    nor->page_size - page_offset, len - i);
 
+               if (nor->flags & SNOR_F_S3AN_ADDR_DEFAULT)
+                       addr = spi_nor_s3an_addr_convert(nor, addr);
+
                write_enable(nor);
-               ret = nor->write(nor, to + i, page_remain, buf + i);
+               ret = nor->write(nor, addr, page_remain, buf + i);
                if (ret < 0)
                        goto write_err;
                written = ret;
@@ -1325,6 +1414,47 @@ static int spi_nor_check(struct spi_nor
        return 0;
 }
 
+static int s3an_nor_scan(const struct flash_info *info, struct spi_nor *nor)
+{
+       int ret;
+       u8 val;
+
+       ret = nor->read_reg(nor, SPINOR_OP_XRDSR, &val, 1);
+       if (ret < 0) {
+               dev_err(nor->dev, "error %d reading XRDSR\n", (int) ret);
+               return ret;
+       }
+
+       nor->erase_opcode = SPINOR_OP_XSE;
+       nor->program_opcode = SPINOR_OP_XPP;
+       nor->read_opcode = SPINOR_OP_READ;
+       nor->flags |= SNOR_F_NO_OP_CHIP_ERASE;
+
+       /*
+        * This flashes have a page size of 264 or 528 bytes (known as
+        * Default addressing mode). It can be changed to a more standard
+        * Power of two mode where the page size is 256/512. This comes
+        * with a price: there is 3% less of space, the data is corrupted
+        * and the page size cannot be changed back to default addressing
+        * mode.
+        *
+        * The current addressing mode can be read from the XRDSR register
+        * and should not be changed, because is a destructive operation.
+        */
+       if (val & XSR_PAGESIZE) {
+               /* Flash in Power of 2 mode */
+               nor->page_size = (nor->page_size == 264) ? 256 : 512;
+               nor->mtd.writebufsize = nor->page_size;
+               nor->mtd.size = 8 * nor->page_size * info->n_sectors;
+               nor->mtd.erasesize = 8 * nor->page_size;
+       } else {
+               /* Flash in Default addressing mode */
+               nor->flags |= SNOR_F_S3AN_ADDR_DEFAULT;
+       }
+
+       return 0;
+}
+
 int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
 {
        const struct flash_info *info = NULL;
@@ -1373,6 +1503,14 @@ int spi_nor_scan(struct spi_nor *nor, co
        mutex_init(&nor->lock);
 
        /*
+        * Make sure the XSR_RDY flag is set before calling
+        * spi_nor_wait_till_ready(). Xilinx S3AN share MFR
+        * with Atmel spi-nor
+        */
+       if (info->flags & SPI_S3AN)
+               nor->flags |=  SNOR_F_READY_XSR_RDY;
+
+       /*
         * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
         * with the software protection bits set
         */
@@ -1530,6 +1668,12 @@ int spi_nor_scan(struct spi_nor *nor, co
 
        nor->read_dummy = spi_nor_read_dummy_cycles(nor);
 
+       if (info->flags & SPI_S3AN) {
+               ret = s3an_nor_scan(info, nor);
+               if (ret)
+                       return ret;
+       }
+
        dev_info(dev, "%s (%lld Kbytes)\n", info->name,
                        (long long)mtd->size >> 10);
 
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -68,6 +68,15 @@
 #define SPINOR_OP_WRDI         0x04    /* Write disable */
 #define SPINOR_OP_AAI_WP       0xad    /* Auto address increment word program */
 
+/* Used for S3AN flashes only */
+#define SPINOR_OP_XSE          0x50    /* Sector erase */
+#define SPINOR_OP_XPP          0x82    /* Page program */
+#define SPINOR_OP_XRDSR                0xd7    /* Read status register */
+
+#define XSR_PAGESIZE           BIT(0)  /* Page size in Po2 or Linear */
+#define XSR_RDY                        BIT(7)  /* Ready */
+
+
 /* Used for Macronix and Winbond flashes. */
 #define SPINOR_OP_EN4B         0xb7    /* Enter 4-byte mode */
 #define SPINOR_OP_EX4B         0xe9    /* Exit 4-byte mode */
@@ -119,6 +128,9 @@ enum spi_nor_ops {
 enum spi_nor_option_flags {
        SNOR_F_USE_FSR          = BIT(0),
        SNOR_F_HAS_SR_TB        = BIT(1),
+       SNOR_F_NO_OP_CHIP_ERASE = BIT(2),
+       SNOR_F_S3AN_ADDR_DEFAULT = BIT(3),
+       SNOR_F_READY_XSR_RDY    = BIT(4),
 };
 
 /**