[PULL 4/5] aspeed/smc: Add support for address lane disablement

["Cédric Le Goater" <clg@kaod.org>]

The controller can be configured to disable or enable address and data
byte lanes when issuing commands. This is useful in read command mode
to send SPI NOR commands that don't have an address space, such as
RDID. It's a good way to have a unified read operation for registers
and flash contents accesses.

A new SPI driver proposed by Aspeed makes use of this feature. Add
support for address lanes to start with. We will do the same for the
data lanes if they are controlled one day.

Cc: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Message-Id: <20201120161547.740806-2-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 hw/ssi/aspeed_smc.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
index 795784e5f364..e3d5e26058c0 100644
--- a/hw/ssi/aspeed_smc.c
+++ b/hw/ssi/aspeed_smc.c
@@ -71,6 +71,16 @@
 #define   INTR_CTRL_CMD_ABORT_EN          (1 << 2)
 #define   INTR_CTRL_WRITE_PROTECT_EN      (1 << 1)
 
+/* Command Control Register */
+#define R_CE_CMD_CTRL      (0x0C / 4)
+#define   CTRL_ADDR_BYTE0_DISABLE_SHIFT       4
+#define   CTRL_DATA_BYTE0_DISABLE_SHIFT       0
+
+#define aspeed_smc_addr_byte_enabled(s, i)                               \
+    (!((s)->regs[R_CE_CMD_CTRL] & (1 << (CTRL_ADDR_BYTE0_DISABLE_SHIFT + (i)))))
+#define aspeed_smc_data_byte_enabled(s, i)                               \
+    (!((s)->regs[R_CE_CMD_CTRL] & (1 << (CTRL_DATA_BYTE0_DISABLE_SHIFT + (i)))))
+
 /* CEx Control Register */
 #define R_CTRL0           (0x10 / 4)
 #define   CTRL_IO_QPI              (1 << 31)
@@ -702,19 +712,17 @@ static void aspeed_smc_flash_setup(AspeedSMCFlash *fl, uint32_t addr)
 {
     const AspeedSMCState *s = fl->controller;
     uint8_t cmd = aspeed_smc_flash_cmd(fl);
-    int i;
+    int i = aspeed_smc_flash_is_4byte(fl) ? 4 : 3;
 
     /* Flash access can not exceed CS segment */
     addr = aspeed_smc_check_segment_addr(fl, addr);
 
     ssi_transfer(s->spi, cmd);
-
-    if (aspeed_smc_flash_is_4byte(fl)) {
-        ssi_transfer(s->spi, (addr >> 24) & 0xff);
+    while (i--) {
+        if (aspeed_smc_addr_byte_enabled(s, i)) {
+            ssi_transfer(s->spi, (addr >> (i * 8)) & 0xff);
+        }
     }
-    ssi_transfer(s->spi, (addr >> 16) & 0xff);
-    ssi_transfer(s->spi, (addr >> 8) & 0xff);
-    ssi_transfer(s->spi, (addr & 0xff));
 
     /*
      * Use fake transfers to model dummy bytes. The value should
@@ -988,6 +996,7 @@ static uint64_t aspeed_smc_read(void *opaque, hwaddr addr, unsigned int size)
         (addr >= s->r_timings &&
          addr < s->r_timings + s->ctrl->nregs_timings) ||
         addr == s->r_ce_ctrl ||
+        addr == R_CE_CMD_CTRL ||
         addr == R_INTR_CTRL ||
         addr == R_DUMMY_DATA ||
         (s->ctrl->has_dma && addr == R_DMA_CTRL) ||
@@ -1276,6 +1285,8 @@ static void aspeed_smc_write(void *opaque, hwaddr addr, uint64_t data,
         if (value != s->regs[R_SEG_ADDR0 + cs]) {
             aspeed_smc_flash_set_segment(s, cs, value);
         }
+    } else if (addr == R_CE_CMD_CTRL) {
+        s->regs[addr] = value & 0xff;
     } else if (addr == R_DUMMY_DATA) {
         s->regs[addr] = value & 0xff;
     } else if (addr == R_INTR_CTRL) {
-- 
2.26.2