Add bridged amplifiers to cs42l43

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

In some cs42l43 systems a couple of cs35l56 amplifiers are attached
to the cs42l43's SPI and I2S. On Windows the cs42l43 is controlled
by a SDCA class driver and these two amplifiers are controlled by
firmware running on the cs42l43. However, under Linux the decision
was made to interact with the cs42l43 directly, affording the user
greater control over the audio system. However, this has resulted
in an issue where these two bridged cs35l56 amplifiers are not
populated in ACPI and must be added manually. There is at least an
SDCA extension unit DT entry we can key off.

The process of adding this is handled using a software node, firstly the
ability to add native chip selects to software nodes must be added.
Secondly, an additional flag for naming the SPI devices is added this
allows the machine driver to key to the correct amplifier. Then finally,
the cs42l43 SPI driver adds the two amplifiers directly onto its SPI
bus.

An additional series will follow soon to add the audio machine driver
parts (in the sof-sdw driver), however that is fairly orthogonal to
this part of the process, getting the actual amplifiers registered.

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c
new file mode 100644
index 000000000000..044219c5960a
--- /dev/null
+++ b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include "i915_drv.h"
+#include "intel_gt.h"
+#include "intel_gt_ccs_mode.h"
+#include "intel_gt_regs.h"
+
+void intel_gt_apply_ccs_mode(struct intel_gt *gt)
+{
+	int cslice;
+	u32 mode = 0;
+	int first_ccs = __ffs(CCS_MASK(gt));
+
+	if (!IS_DG2(gt->i915))
+		return;
+
+	/* Build the value for the fixed CCS load balancing */
+	for (cslice = 0; cslice < I915_MAX_CCS; cslice++) {
+		if (CCS_MASK(gt) & BIT(cslice))
+			/*
+			 * If available, assign the cslice
+			 * to the first available engine...
+			 */
+			mode |= XEHP_CCS_MODE_CSLICE(cslice, first_ccs);
+
+		else
+			/*
+			 * ... otherwise, mark the cslice as
+			 * unavailable if no CCS dispatches here
+			 */
+			mode |= XEHP_CCS_MODE_CSLICE(cslice,
+						     XEHP_CCS_MODE_CSLICE_MASK);
+	}
+
+	intel_uncore_write(gt->uncore, XEHP_CCS_MODE, mode);
+}