mtd: chips: Add support for PMC SPI Flash chips in m25p80.c

Add support for PMC (now Chingis, part of ISSI) Pm25LV512 (512 Kib),
Pm25LV010 (1 Mib) and Pm25LQ032 (32 Mib) SPI Flash chips.

This patch addresses two generations of PMC SPI Flash chips:

 - Pm25LV512 and Pm25LV010: these have 4KiB sectors and 32KiB
   blocks. The 4KiB sector erase uses a non-standard opcode
   (0xd7). They do not support JEDEC RDID (0x9f), and so they can only
   be detected by matching their name string with pre-configured
   platform data. Because of the cascaded acquisitions, the datasheet
   is no longer available on the current manufacturer's website,
   although it is still commonly used in some recent wireless routers
   (<https://forum.openwrt.org/viewtopic.php?pid=186360#p186360>). The
   only public datasheet available seems to be on GeoCities:
   <http://www.geocities.jp/scottle556/pdf/Pm25LV512-010.pdf>

 - Pm25LQ032: a newer generation flash, with 4KiB sectors and 64KiB
   blocks. It uses the standard erase and JEDEC read-ID
   opcodes. Manufacturer's datasheet is here:
   <http://www.chingistek.com/img/Product_Files/Pm25LQ032C%20datasheet%20v1.6.1.pdf>

This patch is resent in order to take into account both Brian Norris
remarks and this upstream patch:

commit e534ee4f9ca29fdb38eea4b0c53f2154fbd8c1ee
Author: Krzysztof Mazur <krzysiek@podlesie.net>
Date:   Fri Feb 22 15:51:05 2013 +0100

    mtd: m25p80: introduce SST_WRITE flag for SST byte programming

    Not all SST devices implement the SST byte programming command.
    Some devices (like SST25VF064C) implement only standard m25p80 page
    write command.

    Now SPI flash devices that need sst_write() are explicitly marked
    with new SST_WRITE flag and the decision to use sst_write() is based
    on this flag instead of manufacturer id.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Michel Stempin <michel.stempin@wanadoo.fr>
[Brian: fixed conflict]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/devices/m25p80.c

@@ -43,6 +43,7 @@
 #define	OPCODE_FAST_READ	0x0b	/* Read data bytes (high frequency) */
 #define	OPCODE_PP		0x02	/* Page program (up to 256 bytes) */
 #define	OPCODE_BE_4K		0x20	/* Erase 4KiB block */
+#define	OPCODE_BE_4K_PMC	0xd7	/* Erase 4KiB block on PMC chips */
 #define	OPCODE_BE_32K		0x52	/* Erase 32KiB block */
 #define	OPCODE_CHIP_ERASE	0xc7	/* Erase whole flash chip */
 #define	OPCODE_SE		0xd8	/* Sector erase (usually 64KiB) */
@@ -692,6 +693,7 @@ struct flash_info {
 #define	M25P_NO_ERASE	0x02		/* No erase command needed */
 #define	SST_WRITE	0x04		/* use SST byte programming */
 #define	M25P_NO_FR	0x08		/* Can't do fastread */
+#define	SECT_4K_PMC	0x10		/* OPCODE_BE_4K_PMC works uniformly */
 };
 
 #define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)	\
@@ -773,6 +775,11 @@ static const struct spi_device_id m25p_ids[] = {
 	{ "n25q128a13",  INFO(0x20ba18, 0, 64 * 1024, 256, 0) },
 	{ "n25q256a", INFO(0x20ba19, 0, 64 * 1024, 512, SECT_4K) },
 
+	/* PMC */
+	{ "pm25lv512", INFO(0, 0, 32 * 1024, 2, SECT_4K_PMC) },
+	{ "pm25lv010", INFO(0, 0, 32 * 1024, 4, SECT_4K_PMC) },
+	{ "pm25lq032", INFO(0x7f9d46, 0, 64 * 1024,  64, SECT_4K) },
+
 	/* Spansion -- single (large) sector size only, at least
 	 * for the chips listed here (without boot sectors).
 	 */
@@ -1026,6 +1033,9 @@ static int m25p_probe(struct spi_device *spi)
 	if (info->flags & SECT_4K) {
 		flash->erase_opcode = OPCODE_BE_4K;
 		flash->mtd.erasesize = 4096;
+	} else if (info->flags & SECT_4K_PMC) {
+		flash->erase_opcode = OPCODE_BE_4K_PMC;
+		flash->mtd.erasesize = 4096;
 	} else {
 		flash->erase_opcode = OPCODE_SE;
 		flash->mtd.erasesize = info->sector_size;