From aaa675f07e781e248fcf169ce9a917b48bc2cc9b Mon Sep 17 00:00:00 2001
From: Brian Norris <computersforpeace@gmail.com>
Date: Fri, 28 Jul 2023 12:06:23 +0200
Subject: [PATCH 3/3] firmware: qcom: scm: fix SCM cold boot address

This effectively reverts upstream Linux commit 13e77747800e ("firmware:
qcom: scm: Use atomic SCM for cold boot"), because Google WiFi boot
firmwares don't support the atomic variant.

This fixes SMP support for Google WiFi.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
 drivers/firmware/qcom_scm-legacy.c | 62 +++++++++++++++++++++++++-----
 drivers/firmware/qcom_scm.c        | 11 ++++++
 2 files changed, 63 insertions(+), 10 deletions(-)

--- a/drivers/firmware/qcom_scm-legacy.c
+++ b/drivers/firmware/qcom_scm-legacy.c
@@ -13,6 +13,9 @@
 #include <linux/arm-smccc.h>
 #include <linux/dma-mapping.h>
 
+#include <asm/cacheflush.h>
+#include <asm/outercache.h>
+
 #include "qcom_scm.h"
 
 static DEFINE_MUTEX(qcom_scm_lock);
@@ -117,6 +120,25 @@ static void __scm_legacy_do(const struct
 	} while (res->a0 == QCOM_SCM_INTERRUPTED);
 }
 
+static void qcom_scm_inv_range(unsigned long start, unsigned long end)
+{
+	u32 cacheline_size, ctr;
+
+	asm volatile("mrc p15, 0, %0, c0, c0, 1" : "=r" (ctr));
+	cacheline_size = 4 << ((ctr >> 16) & 0xf);
+
+	start = round_down(start, cacheline_size);
+	end = round_up(end, cacheline_size);
+	outer_inv_range(start, end);
+	while (start < end) {
+		asm ("mcr p15, 0, %0, c7, c6, 1" : : "r" (start)
+		     : "memory");
+		start += cacheline_size;
+	}
+	dsb();
+	isb();
+}
+
 /**
  * scm_legacy_call() - Sends a command to the SCM and waits for the command to
  * finish processing.
@@ -163,10 +185,16 @@ int scm_legacy_call(struct device *dev,
 
 	rsp = scm_legacy_command_to_response(cmd);
 
-	cmd_phys = dma_map_single(dev, cmd, alloc_len, DMA_TO_DEVICE);
-	if (dma_mapping_error(dev, cmd_phys)) {
-		kfree(cmd);
-		return -ENOMEM;
+	if (dev) {
+		cmd_phys = dma_map_single(dev, cmd, alloc_len, DMA_TO_DEVICE);
+		if (dma_mapping_error(dev, cmd_phys)) {
+			kfree(cmd);
+			return -ENOMEM;
+		}
+	} else {
+		cmd_phys = virt_to_phys(cmd);
+		__cpuc_flush_dcache_area(cmd, alloc_len);
+		outer_flush_range(cmd_phys, cmd_phys + alloc_len);
 	}
 
 	smc.args[0] = 1;
@@ -182,13 +210,26 @@ int scm_legacy_call(struct device *dev,
 		goto out;
 
 	do {
-		dma_sync_single_for_cpu(dev, cmd_phys + sizeof(*cmd) + cmd_len,
-					sizeof(*rsp), DMA_FROM_DEVICE);
+		if (dev) {
+			dma_sync_single_for_cpu(dev, cmd_phys + sizeof(*cmd) +
+						cmd_len, sizeof(*rsp),
+						DMA_FROM_DEVICE);
+		} else {
+			unsigned long start = (uintptr_t)cmd + sizeof(*cmd) +
+					      cmd_len;
+			qcom_scm_inv_range(start, start + sizeof(*rsp));
+		}
 	} while (!rsp->is_complete);
 
-	dma_sync_single_for_cpu(dev, cmd_phys + sizeof(*cmd) + cmd_len +
-				le32_to_cpu(rsp->buf_offset),
-				resp_len, DMA_FROM_DEVICE);
+	if (dev) {
+		dma_sync_single_for_cpu(dev, cmd_phys + sizeof(*cmd) + cmd_len +
+					le32_to_cpu(rsp->buf_offset),
+					resp_len, DMA_FROM_DEVICE);
+	} else {
+		unsigned long start = (uintptr_t)cmd + sizeof(*cmd) + cmd_len +
+				      le32_to_cpu(rsp->buf_offset);
+		qcom_scm_inv_range(start, start + resp_len);
+	}
 
 	if (res) {
 		res_buf = scm_legacy_get_response_buffer(rsp);
@@ -196,7 +237,8 @@ int scm_legacy_call(struct device *dev,
 			res->result[i] = le32_to_cpu(res_buf[i]);
 	}
 out:
-	dma_unmap_single(dev, cmd_phys, alloc_len, DMA_TO_DEVICE);
+	if (dev)
+		dma_unmap_single(dev, cmd_phys, alloc_len, DMA_TO_DEVICE);
 	kfree(cmd);
 	return ret;
 }
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -315,6 +315,17 @@ static int qcom_scm_set_boot_addr(void *
 	desc.args[0] = flags;
 	desc.args[1] = virt_to_phys(entry);
 
+	/*
+	 * Factory firmware doesn't support the atomic variant. Non-atomic SCMs
+	 * require ugly DMA invalidation support that was dropped upstream a
+	 * while ago. For more info, see:
+	 *
+	 *  [RFC] qcom_scm: IPQ4019 firmware does not support atomic API?
+	 *  https://lore.kernel.org/linux-arm-msm/20200913201608.GA3162100@bDebian/
+	 */
+	if (of_machine_is_compatible("google,wifi"))
+		return qcom_scm_call(__scm ? __scm->dev : NULL, &desc, NULL);
+
 	return qcom_scm_call_atomic(__scm ? __scm->dev : NULL, &desc, NULL);
 }
 
