[PATCH 1/4] ddr: imx: Reload the training firmware for every PHY configuration

[Frieder Schrempf <frieder@fris.de>]

From: Frieder Schrempf <frieder.schrempf@kontron.de>

ddr_load_train_firmware() remembers the type of the last loaded firmware
image in a static variable and returns early if the same type is
requested again. That is valid within a single ddr_cfg_phy() call, where
the 1D image is used for several frequency setpoints in a row, but the
state also survives across calls.

Boards that probe several DDR configurations call ddr_init() more than
once. The power up procedure at the beginning of ddr_init() resets the
DDR PHY, which leaves the image in the PHY memory in an undefined state.
The second call then skips the loading, starts the PMU on whatever is
left of it and the training firmware never reports a result. As the PHY
also stops answering on its APB interface at that point, the boot hangs
in a register read, which no software timeout can recover from.

On some specific Kontron SL i.MX8MM with 1GB or 2GB DDR, where the first
init is expected to fail and the second one uses an adjusted
configuration, this made the boot hang every few cycles.

Move the check into ddr_cfg_phy(), the only caller, so that the loading
is still skipped for repeated setpoints of one run, but never across
runs.

Fixes: b614ddb5d335 ("ddr: imx: Save the FW loading if it hasn't changed")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
---
 drivers/ddr/imx/phy/ddrphy_train.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/ddr/imx/phy/ddrphy_train.c b/drivers/ddr/imx/phy/ddrphy_train.c
index 1a2d071d6f1..63a6ca800a3 100644
--- a/drivers/ddr/imx/phy/ddrphy_train.c
+++ b/drivers/ddr/imx/phy/ddrphy_train.c
@@ -12,6 +12,7 @@ int ddr_cfg_phy(struct dram_timing_info *dram_timing)
 {
 	struct dram_cfg_param *dram_cfg;
 	struct dram_fsp_msg *fsp_msg;
+	int last_fw_type = -1;
 	unsigned int num;
 	int i = 0;
 	int j = 0;
@@ -33,9 +34,18 @@ int ddr_cfg_phy(struct dram_timing_info *dram_timing)
 		/* set dram PHY input clocks to desired frequency */
 		ddrphy_init_set_dfi_clk(fsp_msg->drate);
 
-		/* load the dram training firmware image */
+		/*
+		 * Load the DRAM training firmware image, unless the same image has
+		 * already been loaded for an earlier frequency setpoint of this run.
+		 * It must be loaded again for every ddr_cfg_phy() call as the caller
+		 * resets the PHY before this, which leaves the image in the PHY memory
+		 * in an undefined state.
+		 */
 		dwc_ddrphy_apb_wr(0xd0000, 0x0);
-		ddr_load_train_firmware(fsp_msg->fw_type);
+		if (fsp_msg->fw_type != last_fw_type) {
+			ddr_load_train_firmware(fsp_msg->fw_type);
+			last_fw_type = fsp_msg->fw_type;
+		}
 
 		/* load the frequency set point message block parameter */
 		dram_cfg = fsp_msg->fsp_cfg;
-- 
2.55.0