From 9fb2eb7470d56d94bd8687b7566d60c3837df3a2 Mon Sep 17 00:00:00 2001
From: Peter Hansen <peter@engcorp.com>
Date: Sun, 3 Dec 2023 16:35:39 -0500
Subject: [PATCH] nrf52/qspi: avoid infinite busy-wait on QSPI read/write with
 zero-len buffer, fixes #2115

---
 embassy-nrf/src/qspi.rs | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)
 mode change 100644 => 100755 embassy-nrf/src/qspi.rs

diff --git a/embassy-nrf/src/qspi.rs b/embassy-nrf/src/qspi.rs
old mode 100644
new mode 100755
index add093b6..5e1a4e84
--- a/embassy-nrf/src/qspi.rs
+++ b/embassy-nrf/src/qspi.rs
@@ -391,8 +391,13 @@ impl<'d, T: Instance> Qspi<'d, T> {
     ///
     /// The difference with `read` is that this does not do bounds checks
     /// against the flash capacity. It is intended for use when QSPI is used as
-    /// a raw bus, not with flash memory.    
+    /// a raw bus, not with flash memory.
     pub async fn read_raw(&mut self, address: u32, data: &mut [u8]) -> Result<(), Error> {
+        // Avoid blocking_wait_ready() blocking forever on zero-length buffers.
+        if data.len() == 0 {
+            return Ok(());
+        }
+
         let ondrop = OnDrop::new(Self::blocking_wait_ready);
 
         self.start_read(address, data)?;
@@ -409,6 +414,11 @@ impl<'d, T: Instance> Qspi<'d, T> {
     /// against the flash capacity. It is intended for use when QSPI is used as
     /// a raw bus, not with flash memory.
     pub async fn write_raw(&mut self, address: u32, data: &[u8]) -> Result<(), Error> {
+        // Avoid blocking_wait_ready() blocking forever on zero-length buffers.
+        if data.len() == 0 {
+            return Ok(());
+        }
+
         let ondrop = OnDrop::new(Self::blocking_wait_ready);
 
         self.start_write(address, data)?;
@@ -425,6 +435,11 @@ impl<'d, T: Instance> Qspi<'d, T> {
     /// against the flash capacity. It is intended for use when QSPI is used as
     /// a raw bus, not with flash memory.
     pub fn blocking_read_raw(&mut self, address: u32, data: &mut [u8]) -> Result<(), Error> {
+        // Avoid blocking_wait_ready() blocking forever on zero-length buffers.
+        if data.len() == 0 {
+            return Ok(());
+        }
+
         self.start_read(address, data)?;
         Self::blocking_wait_ready();
         Ok(())
@@ -436,6 +451,11 @@ impl<'d, T: Instance> Qspi<'d, T> {
     /// against the flash capacity. It is intended for use when QSPI is used as
     /// a raw bus, not with flash memory.
     pub fn blocking_write_raw(&mut self, address: u32, data: &[u8]) -> Result<(), Error> {
+        // Avoid blocking_wait_ready() blocking forever on zero-length buffers.
+        if data.len() == 0 {
+            return Ok(());
+        }
+
         self.start_write(address, data)?;
         Self::blocking_wait_ready();
         Ok(())