[PATCH 2/3] mtd: m25p80: make CONFIG_M25PXX_USE_FAST_READ safe to enable

[Sascha Hauer <s.hauer@pengutronix.de>]

This patch adds a flag to struct flash_info indicating that
fast_read is not supported. This now gives the following logic
when determing whether to enable fastread:

If the flash chip does not support fast_read, then disable it.
Otherwise:
1) enable fast_read if device node contains m25p,fast-read
2) enable fast_read if forced in Kconfig

This makes enabling CONFIG_M25PXX_USE_FAST_READ a safe option
since we no longer enable the fast_read option unconditionally.

For now fast_read is disabled for the everspin mr25h256 and the
catalyst devices. Others may need the flag aswell.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/mtd/devices/m25p80.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 0b8672b..6f93d32 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -691,6 +691,7 @@ struct flash_info {
 #define	SECT_4K		0x01		/* OPCODE_BE_4K works uniformly */
 #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 INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)	\
@@ -741,7 +742,7 @@ static const struct spi_device_id m25p_ids[] = {
 	{ "en25qh256", INFO(0x1c7019, 0, 64 * 1024, 512, 0) },
 
 	/* Everspin */
-	{ "mr25h256", CAT25_INFO(  32 * 1024, 1, 256, 2, M25P_NO_ERASE) },
+	{ "mr25h256", CAT25_INFO(  32 * 1024, 1, 256, 2, M25P_NO_ERASE | M25P_NO_FR) },
 
 	/* GigaDevice */
 	{ "gd25q32", INFO(0xc84016, 0, 64 * 1024,  64, SECT_4K) },
@@ -856,11 +857,11 @@ static const struct spi_device_id m25p_ids[] = {
 	{ "w25q256", INFO(0xef4019, 0, 64 * 1024, 512, SECT_4K) },
 
 	/* Catalyst / On Semiconductor -- non-JEDEC */
-	{ "cat25c11", CAT25_INFO(  16, 8, 16, 1, M25P_NO_ERASE) },
-	{ "cat25c03", CAT25_INFO(  32, 8, 16, 2, M25P_NO_ERASE) },
-	{ "cat25c09", CAT25_INFO( 128, 8, 32, 2, M25P_NO_ERASE) },
-	{ "cat25c17", CAT25_INFO( 256, 8, 32, 2, M25P_NO_ERASE) },
-	{ "cat25128", CAT25_INFO(2048, 8, 64, 2, M25P_NO_ERASE) },
+	{ "cat25c11", CAT25_INFO(  16, 8, 16, 1, M25P_NO_ERASE | M25P_NO_FR) },
+	{ "cat25c03", CAT25_INFO(  32, 8, 16, 2, M25P_NO_ERASE | M25P_NO_FR) },
+	{ "cat25c09", CAT25_INFO( 128, 8, 32, 2, M25P_NO_ERASE | M25P_NO_FR) },
+	{ "cat25c17", CAT25_INFO( 256, 8, 32, 2, M25P_NO_ERASE | M25P_NO_FR) },
+	{ "cat25128", CAT25_INFO(2048, 8, 64, 2, M25P_NO_ERASE | M25P_NO_FR) },
 	{ },
 };
 MODULE_DEVICE_TABLE(spi, m25p_ids);
@@ -1044,6 +1045,8 @@ static int m25p_probe(struct spi_device *spi)
 #ifdef CONFIG_M25PXX_USE_FAST_READ
 	flash->fast_read = true;
 #endif
+	if (info->flags & M25P_NO_FR)
+		flash->fast_read = false;
 
 	/* Default commands */
 	if (flash->fast_read)
-- 
1.8.4.rc3