[PATCH 2/2] rockchip: rk3399: enable spl-fifo-mode for sdmmc only when needed

[Jerome Forissier]

Commit 5c606ca35c42 ("rockchip: rk3399: enable spl-fifo-mode for sdmmc")
mentions that the RK3399 SoC can't do DMA between SDMMC and SRAM.
According to the TRM "7.3.2 Embedded SRAM access path" [1], only the
8KB SRAM at 0xff3b0000 (INTMEM1) is in this situation. The 192KB SRAM
can be accessed by both DMA controllers.

Assuming the only use case for writing from MMC to INTMEM1 is loading
a FIT image, and with the introduction of a temporary buffer for that
purpose (CONFIG_SPL_LOAD_FIT_IMAGE_BUFFER_SIZE, which is required
anyways to ensure the destination boundaries are enforced), then
spl-fifo-mode is not needed anymore and DMA can be enabled safely.

Link: [1] https://www.rockchip.fr/Rockchip%20RK3399%20TRM%20V1.4%20Part1.pdf
CC: Deepak Das <deepakdas.linux at gmail.com>
Signed-off-by: Jerome Forissier <jerome.forissier at linaro.org>
---
 arch/arm/dts/rk3399-u-boot.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/dts/rk3399-u-boot.dtsi b/arch/arm/dts/rk3399-u-boot.dtsi
index 716b9a433a..a1b6d6f007 100644
--- a/arch/arm/dts/rk3399-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-u-boot.dtsi
@@ -124,8 +124,10 @@
 &sdmmc {
 	u-boot,dm-pre-reloc;
 
+#ifndef CONFIG_SPL_LOAD_FIT_IMAGE_BUFFER_SIZE
 	/* mmc to sram can't do dma, prevent aborts transferring TF-A parts */
 	u-boot,spl-fifo-mode;
+#endif
 };
 
 &spi1 {
-- 
2.34.1