acp_7_x: clear DMA IO stutter and PWA defaults to fix I2S loopback noise

ACP DMA linked-list, IO stutter, and PWA control registers retain
power-on defaults that can affect I2S DMA transfers:

- ACP_DMA_CH_LINKED_LIST_EN: DMAChIOStutEn (bits 24:15) defaults to all 1s
- ACP_DMA_IO_STUT_TIMER_LIMIT: IO stutter timer defaults are non-zero
- ACP_DMA_CH_PWA_CTRL: PWA DMA control defaults are enabled

Clear these registers during platform init, before DMA channel setup,
to disable DMA IO stutter and PWA features that cause I2S loopback noise.

Signed-off-by: sneha-voona <sneha.voona@amd.com>

Author: sneha-voona

src/platform/amd/acp_7_x/include/platform/platform_misc.h

@@ -24,6 +24,9 @@
 #define ACP_SRBM_CLIENT_RDDATA         0x1241BF4
 #define ACP_SRBM_CYCLE_STS             0x1241BF8
 #define ACP_SRBM_CLIENT_CONFIG         0x1241BFC
+#define ACP_DMA_CH_LINKED_LIST_EN      0x124012C
+#define ACP_DMA_IO_STUT_TIMER_LIMIT    0x1240130
+#define ACP_DMA_CH_PWA_CTRL            0x1240138
 
 /* Registers from SYSTEMPLL2P0_N3_BUS_CSR_SNAP_6 block ACP_7X */
 #define ACP_7X_SYSTEMPLL2P0_N3_BUS_CSR_SNAP_6_REFCLK_BRDS            0x6D204

src/platform/amd/acp_7_x/platform.c

@@ -150,6 +150,16 @@ int platform_init(struct sof *sof)
 	/*CONFIG_SYSTICK_PERIOD hardcoded as 200000*/
 	sa_init(sof, 200000);
 	clock_set_freq(CLK_CPU(cpu_get_id()), CLK_MAX_CPU_HZ);
+
+	/*
+	 * Clear DMA linked-list IO stutter and PWA defaults before
+	 * channel setup. ACP_DMA_CH_LINKED_LIST_EN DMAChIOStutEn
+	 * (bits 24:15) defaults to all 1s.
+	 */
+	io_reg_write(PU_REGISTER_BASE + ACP_DMA_CH_LINKED_LIST_EN, 0);
+	io_reg_write(PU_REGISTER_BASE + ACP_DMA_IO_STUT_TIMER_LIMIT, 0);
+	io_reg_write(PU_REGISTER_BASE + ACP_DMA_CH_PWA_CTRL, 0);
+
 	/* init DMA */
 	ret = dmac_init(sof);
 	if (ret < 0) {