memory: tegra186-emc: Handle errors in BPMP response

The return value from tegra_bpmp_transfer indicates the success or
failure of the IPC transaction with BPMP. If the transaction
succeeded, we also need to check the actual command's result code.
Add code to do this.
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Link: https://lore.kernel.org/r/20210915085517.1669675-3-mperttunen@nvidia.comSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

drivers/memory/tegra/tegra186-emc.c

@@ -197,6 +197,10 @@ static int tegra186_emc_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "failed to EMC DVFS pairs: %d\n", err);
 		goto put_bpmp;
 	}
+	if (msg.rx.ret < 0) {
+		dev_err(&pdev->dev, "EMC DVFS MRQ failed: %d (BPMP error code)\n", msg.rx.ret);
+		goto put_bpmp;
+	}
 
 	emc->debugfs.min_rate = ULONG_MAX;
 	emc->debugfs.max_rate = 0;