m25p80: Add basic support for the SFDP command

JEDEC STANDARD JESD216 for Serial Flash Discovery Parameters (SFDP)
provides a mean to describe the features of a serial flash device
using a set of internal parameter tables.

This is the initial framework for the RDSFDP command giving access to
a private SFDP area under the flash. This area now needs to be
populated with the flash device characteristics, using a new
'sfdp_read' handler under FlashPartInfo.

Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Message-Id: <20220722063602.128144-2-clg@kaod.org>
Message-Id: <20221013161241.2805140-2-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

MAINTAINERS

@@ -1915,7 +1915,7 @@ SSI
 M: Alistair Francis <alistair@alistair23.me>
 S: Maintained
 F: hw/ssi/*
-F: hw/block/m25p80.c
+F: hw/block/m25p80*
 F: include/hw/ssi/ssi.h
 X: hw/ssi/xilinx_*
 F: tests/qtest/m25p80-test.c

hw/block/m25p80.c

@@ -35,6 +35,7 @@
 #include "qapi/error.h"
 #include "trace.h"
 #include "qom/object.h"
+#include "m25p80_sfdp.h"
 
 /* 16 MiB max in 3 byte address mode */
 #define MAX_3BYTES_SIZE 0x1000000
@@ -72,6 +73,7 @@ typedef struct FlashPartInfo {
      * This field inform how many die is in the chip.
      */
     uint8_t die_cnt;
+    uint8_t (*sfdp_read)(uint32_t sfdp_addr);
 } FlashPartInfo;
 
 /* adapted from linux */
@@ -355,6 +357,7 @@ typedef enum {
     BULK_ERASE = 0xc7,
     READ_FSR = 0x70,
     RDCR = 0x15,
+    RDSFDP = 0x5a,
 
     READ = 0x03,
     READ4 = 0x13,
@@ -421,6 +424,7 @@ typedef enum {
     STATE_COLLECTING_DATA,
     STATE_COLLECTING_VAR_LEN_DATA,
     STATE_READING_DATA,
+    STATE_READING_SFDP,
 } CMDState;
 
 typedef enum {
@@ -679,6 +683,8 @@ static inline int get_addr_length(Flash *s)
     }
 
    switch (s->cmd_in_progress) {
+   case RDSFDP:
+       return 3;
    case PP4:
    case PP4_4:
    case QPP_4:
@@ -823,6 +829,11 @@ static void complete_collecting_data(Flash *s)
                           " by device\n");
         }
         break;
+
+    case RDSFDP:
+        s->state = STATE_READING_SFDP;
+        break;
+
     default:
         break;
     }
@@ -1431,6 +1442,16 @@ static void decode_new_cmd(Flash *s, uint32_t value)
             qemu_log_mask(LOG_GUEST_ERROR, "M25P80: Unknown cmd %x\n", value);
         }
         break;
+    case RDSFDP:
+        if (s->pi->sfdp_read) {
+            s->needed_bytes = get_addr_length(s) + 1; /* SFDP addr + dummy */
+            s->pos = 0;
+            s->len = 0;
+            s->state = STATE_COLLECTING_DATA;
+            break;
+        }
+        /* Fallthrough */
+
     default:
         s->pos = 0;
         s->len = 1;
@@ -1538,6 +1559,12 @@ static uint32_t m25p80_transfer8(SSIPeripheral *ss, uint32_t tx)
             }
         }
         break;
+    case STATE_READING_SFDP:
+        assert(s->pi->sfdp_read);
+        r = s->pi->sfdp_read(s->cur_addr);
+        trace_m25p80_read_sfdp(s, s->cur_addr, (uint8_t)r);
+        s->cur_addr = (s->cur_addr + 1) & (M25P80_SFDP_MAX_SIZE - 1);
+        break;
 
     default:
     case STATE_IDLE:

hw/block/m25p80_sfdp.h

@@ -0,0 +1,18 @@
+/*
+ * M25P80 SFDP
+ *
+ * Copyright (c) 2020, IBM Corporation.
+ *
+ * This code is licensed under the GPL version 2 or later. See the
+ * COPYING file in the top-level directory.
+ */
+
+#ifndef HW_M25P80_SFDP_H
+#define HW_M25P80_SFDP_H
+
+/*
+ * SFDP area has a 3 bytes address space.
+ */
+#define M25P80_SFDP_MAX_SIZE  (1 << 24)
+
+#endif

hw/block/trace-events

@@ -80,5 +80,6 @@ m25p80_page_program(void *s, uint32_t addr, uint8_t tx) "[%p] page program cur_a
 m25p80_transfer(void *s, uint8_t state, uint32_t len, uint8_t needed, uint32_t pos, uint32_t cur_addr, uint8_t t) "[%p] Transfer state 0x%"PRIx8" len 0x%"PRIx32" needed 0x%"PRIx8" pos 0x%"PRIx32" addr 0x%"PRIx32" tx 0x%"PRIx8
 m25p80_read_byte(void *s, uint32_t addr, uint8_t v) "[%p] Read byte 0x%"PRIx32"=0x%"PRIx8
 m25p80_read_data(void *s, uint32_t pos, uint8_t v) "[%p] Read data 0x%"PRIx32"=0x%"PRIx8
+m25p80_read_sfdp(void *s, uint32_t addr, uint8_t v) "[%p] Read SFDP 0x%"PRIx32"=0x%"PRIx8
 m25p80_binding(void *s) "[%p] Binding to IF_MTD drive"
 m25p80_binding_no_bdrv(void *s) "[%p] No BDRV - binding to RAM"