[RFC PATCH 3/3] mtd: spi-nor: Parse SFDP SCCR Map

[Tudor Ambarus]

Parse just the 22nd dword and look for the 'DTR Octal Mode Enable
Volatile bit'.

SPI_NOR_IO_MODE_EN_VOLATILE should be set just for the flashes
that don't define the optional SFDP SCCR Map. For the others,
let the SFDP do its job and fill the SNOR_F_IO_MODE_EN_VOLATILE
flag. We avoid this way polluting the flash flags when declaring
one.

Signed-off-by: Tudor Ambarus <tudor.amba...@microchip.com>
---
 drivers/mtd/spi-nor/sfdp.c | 52 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index f192710aca31..7bca64cbba02 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -21,6 +21,10 @@
 #define SFDP_SECTOR_MAP_ID     0xff81  /* Sector Map Table */
 #define SFDP_4BAIT_ID          0xff84  /* 4-byte Address Instruction Table */
 #define SFDP_PROFILE1_ID       0xff05  /* xSPI Profile 1.0 table. */
+#define SFDP_SCCR_MAP_ID       0xff87  /*
+                                        * Status, Control and Configuration
+                                        * Register Map.
+                                        */
 
 #define SFDP_SIGNATURE         0x50444653U
 
@@ -1199,6 +1203,50 @@ static int spi_nor_parse_profile1(struct spi_nor *nor,
        return ret;
 }
 
+#define SCCR_DWORD22_OCTAL_DTR_EN_VOLATILE             BIT(31)
+
+/**
+ * spi_nor_parse_sccr() - Parse the Status, Control and Configuration Register
+ *                        Map.
+ * @nor:               pointer to a 'struct spi_nor'
+ * @sccr_header:       pointer to the 'struct sfdp_parameter_header' describing
+ *                     the SCCR Map table length and version.
+ * @params:            pointer to the 'struct spi_nor_flash_parameter' to be.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_parse_sccr(struct spi_nor *nor,
+                             const struct sfdp_parameter_header *sccr_header,
+                             struct spi_nor_flash_parameter *params)
+{
+       u32 *dwords, addr;
+       size_t len;
+       int ret;
+       u8 io_mode_en_volatile;
+
+       len = sccr_header->length * sizeof(*dwords);
+       dwords = kmalloc(len, GFP_KERNEL);
+       if (!dwords)
+               return -ENOMEM;
+
+       addr = SFDP_PARAM_HEADER_PTP(sccr_header);
+       ret = spi_nor_read_sfdp(nor, addr, len, dwords);
+       if (ret)
+               goto out;
+
+       le32_to_cpu_array(dwords, sccr_header->length);
+
+       io_mode_en_volatile = FIELD_GET(SCCR_DWORD22_OCTAL_DTR_EN_VOLATILE,
+                                       dwords[22]);
+
+       if (io_mode_en_volatile)
+               nor->flags |= SNOR_F_IO_MODE_EN_VOLATILE;
+
+out:
+       kfree(dwords);
+       return ret;
+}
+
 /**
  * spi_nor_parse_sfdp() - parse the Serial Flash Discoverable Parameters.
  * @nor:               pointer to a 'struct spi_nor'
@@ -1304,6 +1352,10 @@ int spi_nor_parse_sfdp(struct spi_nor *nor,
                        err = spi_nor_parse_profile1(nor, param_header, params);
                        break;
 
+               case SFDP_SCCR_MAP_ID:
+                       err = spi_nor_parse_sccr(nor, param_header, params);
+                       break;
+
                default:
                        break;
                }
-- 
2.25.1