spi: Fix build for Linux v6.8

For Linux v6.8, support for SPI controllers with multiple chip-selects
was added to the SPI core and this updated the 'chip_select' member of
the 'spi_device' structure to be an array. This breaks building the
Tegra124 SPI Slave driver and Tegra210 QUAD SPI driver.

A helper function, spi_get_chipselect(), was added for Linux v6.3 to
retrieve the chip-select for a SPI device and can be used for retrieving
the chip-select for all Linux v6.3+ kernels.

Add a conftest rule to detecting if spi_get_chipselect() is present and
if so use this for getting the chip-select. This fixes the build issues
for Linux v6.8.

Bug 4448428

Change-Id: Ia4f95ed96b9a18cc7da7a4a52305fc64bc31905c
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3050146
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

drivers/spi/spi-tegra124-slave.c

@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
-// SPDX-FileCopyrightText: Copyright (C) 2023 NVIDIA CORPORATION.  All rights reserved.
+// SPDX-FileCopyrightText: Copyright (C) 2023-2024 NVIDIA CORPORATION.  All rights reserved.
+
+#include <nvidia/conftest.h>
 
 #include <linux/clk.h>
 #include <linux/reset.h>
@@ -1357,7 +1359,11 @@ static int tegra_spi_start_transfer_one(struct spi_device *spi,
 		command1 |= SPI_TX_EN;
 		tspi->cur_direction |= DATA_DIR_TX;
 	}
+#if defined(NV_SPI_GET_CHIPSELECT_PRESENT)
+	command1 |= SPI_CS_SEL(spi_get_chipselect(spi, 0));
+#else
 	command1 |= SPI_CS_SEL(spi->chip_select);
+#endif
 	tegra_spi_writel(tspi, command1, SPI_COMMAND1);
 	tspi->command1_reg = command1;
 
@@ -1398,7 +1404,11 @@ static struct tegra_spi_controller_data
 		return NULL;
 	}
 
+#if defined(NV_SPI_GET_CHIPSELECT_PRESENT)
+	cdata = &tspi->cdata[spi_get_chipselect(spi, 0)];
+#else
 	cdata = &tspi->cdata[spi->chip_select];
+#endif
 	memset(cdata, 0, sizeof(*cdata));
 
 	ret = of_property_read_bool(data_np, "nvidia,variable-length-transfer");
@@ -1448,10 +1458,17 @@ static int tegra_spi_setup(struct spi_device *spi)
 
 	spin_lock_irqsave(&tspi->lock, flags);
 	val = tspi->def_command1_reg;
+#if defined(NV_SPI_GET_CHIPSELECT_PRESENT)
+	if (spi->mode & SPI_CS_HIGH)
+		val &= ~cs_pol_bit[spi_get_chipselect(spi, 0)];
+	else
+		val |= cs_pol_bit[spi_get_chipselect(spi, 0)];
+#else
 	if (spi->mode & SPI_CS_HIGH)
 		val &= ~cs_pol_bit[spi->chip_select];
 	else
 		val |= cs_pol_bit[spi->chip_select];
+#endif
 
 	if (tspi->lsbyte_first)
 		val |= SPI_LSBYTE_FE;

drivers/spi/spi-tegra210-quad.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
-//
-// Copyright (C) 2023 NVIDIA CORPORATION.
+// SPDX-FileCopyrightText: Copyright (C) 2023-2024 NVIDIA CORPORATION.  All rights reserved.
+
+#include <nvidia/conftest.h>
 
 #include <linux/clk.h>
 #include <linux/completion.h>
@@ -925,7 +926,11 @@ static u32 tegra_qspi_setup_transfer_one(struct spi_device *spi, struct spi_tran
 		tegra_qspi_mask_clear_irq(tqspi);
 
 		command1 = tqspi->def_command1_reg;
+#if defined(NV_SPI_GET_CHIPSELECT_PRESENT)
+		command1 |= QSPI_CS_SEL(spi_get_chipselect(spi, 0));
+#else
 		command1 |= QSPI_CS_SEL(spi->chip_select);
+#endif
 		command1 |= QSPI_BIT_LENGTH(bits_per_word - 1);
 
 		command1 &= ~QSPI_CONTROL_MODE_MASK;
@@ -1109,11 +1114,21 @@ static int tegra_qspi_setup(struct spi_device *spi)
 
 	/* keep default cs state to inactive */
 	val = tqspi->def_command1_reg;
+#if defined(NV_SPI_GET_CHIPSELECT_PRESENT)
+	val |= QSPI_CS_SEL(spi_get_chipselect(spi, 0));
+
+	if (spi->mode & SPI_CS_HIGH)
+		val &= ~QSPI_CS_POL_INACTIVE(spi_get_chipselect(spi, 0));
+	else
+		val |= QSPI_CS_POL_INACTIVE(spi_get_chipselect(spi, 0));
+#else
 	val |= QSPI_CS_SEL(spi->chip_select);
+
 	if (spi->mode & SPI_CS_HIGH)
 		val &= ~QSPI_CS_POL_INACTIVE(spi->chip_select);
 	else
 		val |= QSPI_CS_POL_INACTIVE(spi->chip_select);
+#endif
 
 	tqspi->def_command1_reg = val;
 	tegra_qspi_writel(tqspi, tqspi->def_command1_reg, QSPI_COMMAND1);

scripts/conftest/Makefile

@@ -1,6 +1,6 @@
 ###########################################################################
 # SPDX-License-Identifier: MIT
-# SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2023-2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 #
 # Makefile file for NVIDIA Linux conftest
 ###########################################################################
@@ -151,6 +151,7 @@ NV_CONFTEST_FUNCTION_COMPILE_TESTS += snd_soc_of_get_dai_name_has_index_arg
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += snd_soc_rtd_to_codec
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += simple_util_dai_init
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += spi_driver_struct_remove_return_type_int
+NV_CONFTEST_FUNCTION_COMPILE_TESTS += spi_get_chipselect
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += tc_taprio_qopt_offload_struct_has_cmd
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += tegra_dev_iommu_get_stream_id
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += tegra_ivc_struct_has_iosys_map

scripts/conftest/conftest.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 # SPDX-License-Identifier: MIT
-# SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2023-2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 
 PATH="${PATH}:/bin:/sbin:/usr/bin"
 
@@ -7463,6 +7463,28 @@ compile_test() {
             compile_check_conftest "$CODE" "NV_SPI_DRIVER_STRUCT_REMOVE_RETURN_TYPE_INT" "" "types"
         ;;
 
+        spi_get_chipselect)
+            #
+            # Determine if the function 'spi_get_chip_select()' is present.
+            #
+            # In Linux v6.3, commit 303feb3cc06a ("spi: Add APIs in spi core to set/get
+            # spi->chip_select and spi->cs_gpiod") added a helper function,
+            # spi_get_chipselect(), so drivers did not need to access the
+            # 'spi_device->chip_select' directly. This Linux v6.8, commit 4d8ff6b0991d
+            # ("spi: Add multi-cs memories support in SPI core") updated the
+            # 'spi_device->chip_select' to be an array and so using spi_get_chipselect
+            # to retrieve the chipselect is required for Linux v6.8.
+            #
+            CODE="
+            #undef CONFIG_ACPI
+            #include <linux/spi/spi.h>
+            void conftest_spi_get_chipselect(void) {
+                spi_get_chipselect();
+            }"
+
+            compile_check_conftest "$CODE" "NV_SPI_GET_CHIPSELECT_PRESENT" "" "functions"
+        ;;
+
         tc_taprio_qopt_offload_struct_has_cmd)
             #
             # Determine if struct tc_taprio_qopt_offload has a member named cmd