From 4b03ccc7cb74801a5f5b58bad7bb2c9c26564c3d Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.com>
Date: Mon, 22 Jul 2024 15:27:51 +0100
Subject: [PATCH] spi: dw: don't immediately kill DMA transfers if an error
 occurs

Disabling the peripheral resets controller state which has a dangerous
side-effect of disabling the DMA handshake interface while it is active.
This can cause DMA channels to hang.

The error recovery pathway will wait for DMA to stop and reset the chip
anyway, so mask further FIFO interrupts and let the transfer finish
gracefully.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
---
 drivers/spi/spi-dw-core.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -202,7 +202,18 @@ int dw_spi_check_status(struct dw_spi *d
 
 	/* Generically handle the erroneous situation */
 	if (ret) {
-		dw_spi_reset_chip(dws);
+		/*
+		 * Forcibly halting the controller can cause DMA to hang.
+		 * Defer to dw_spi_handle_err outside of interrupt context
+		 * and mask further interrupts for the current transfer.
+		 */
+		if (dws->dma_mapped) {
+			dw_spi_mask_intr(dws, 0xff);
+			dw_readl(dws, DW_SPI_ICR);
+		} else {
+			dw_spi_reset_chip(dws);
+		}
+
 		if (dws->host->cur_msg)
 			dws->host->cur_msg->status = ret;
 	}
