add restore logic for erase test.

target/ast10x0/peripherals/smc/device/flash.rs

diff --git a/target/ast10x0/peripherals/smc/device/flash.rs b/target/ast10x0/peripherals/smc/device/flash.rs
index 062409e..3815cfe 100644
--- a/target/ast10x0/peripherals/smc/device/flash.rs
+++ b/target/ast10x0/peripherals/smc/device/flash.rs
@@ -508,6 +508,8 @@
         self.validate_range(offset, buf.len())?;
         let translated = self.device_to_controller_offset(offset)?;
         let cs = self.cs;
+        //TODO: need to add dma_read variant if buf.len() is above some threshold
+        // and dma is enabled
         match &self.backend {
             FlashBackend::Fmc(fmc) => fmc.read(cs, translated, buf),
             FlashBackend::Spi(spi) => spi.read(cs, translated, buf),

target/ast10x0/tests/smc/write/target.rs

diff --git a/target/ast10x0/tests/smc/write/target.rs b/target/ast10x0/tests/smc/write/target.rs
index ef5eb1d..cee181f 100644
--- a/target/ast10x0/tests/smc/write/target.rs
+++ b/target/ast10x0/tests/smc/write/target.rs
@@ -39,6 +39,7 @@
 
 const TEST_OFFSET: u32 = 0x10_0000;
 const TEST_LEN: usize = 256;
+const TEST_SECTOR_LEN: usize = 4096;
 
 pub struct Target {}
 
@@ -59,6 +60,22 @@
     Ok(())
 }
 
+fn restore_sector(flash: &mut SpiNorFlash<'_>, original: &[u8]) -> Result<(), SmcError> {
+    pw_log::info!("=== restore CS1 sector ===");
+    flash.erase_sector(TEST_OFFSET)?;
+
+    let written = flash.program(TEST_OFFSET, original)?;
+    if written != TEST_SECTOR_LEN {
+        return Err(SmcError::HardwareError);
+    }
+
+    if !flash.verify(TEST_OFFSET, original)? {
+        return Err(SmcError::HardwareError);
+    }
+
+    Ok(())
+}
+
 fn run_smc_fmc_cs1_write_test() -> Result<(), SmcError> {
     let scu = unsafe { ScuRegisters::new_global_unlocked() };
     scu.apply_pinctrl_group(PINCTRL_FMC_QUAD);
@@ -81,8 +98,10 @@
         return Err(SmcError::HardwareError);
     }
 
-    let mut flash = SpiNorFlash::from_fmc_cs(&mut fmc, CS1_CONFIG, ChipSelect::Cs1)?;
-    let jedec = flash.jedec_id()?;
+    let jedec = {
+        let flash = SpiNorFlash::from_fmc_cs(&mut fmc, CS1_CONFIG, ChipSelect::Cs1)?;
+        flash.jedec_id()?
+    };
     pw_log::info!(
         "CS1 JEDEC ID: {:02x} {:02x} {:02x}",
         jedec[0] as u32,
@@ -90,6 +109,26 @@
         jedec[2] as u32
     );
 
+    pw_log::info!("=== backup CS1 sector ===");
+    let original = unsafe { core::slice::from_raw_parts_mut(0x41000 as *mut u8, TEST_SECTOR_LEN) };
+    fmc.dma_read(
+        ChipSelect::Cs1,
+        TEST_OFFSET,
+        0x41000usize,
+        TEST_SECTOR_LEN as u32,
+    )?;
+    loop {
+        match fmc.poll_dma_completion() {
+            core::task::Poll::Pending => {}
+            core::task::Poll::Ready(result) => {
+                result?;
+                break;
+            }
+        }
+    }
+
+    let mut flash = SpiNorFlash::from_fmc_cs(&mut fmc, CS1_CONFIG, ChipSelect::Cs1)?;
+
     pw_log::info!("=== erase CS1 sector ===");
     flash.erase_sector(TEST_OFFSET)?;
 
@@ -122,6 +161,8 @@
         return Err(SmcError::HardwareError);
     }
 
+    restore_sector(&mut flash, original)?;
+
     dump_smc_register(0x7E62_0000, 16);
     Ok(())
 }