linux-kernel - [PATCH] dmaengine: apple-admac: Avoid accessing registers in probe

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Message-Id: <20241124-admac-power-v1-1-58f2165a4d55@gmail.com>
Date: Sun, 24 Nov 2024 16:48:28 +0100
From: Sasha Finkelstein via B4 Relay <devnull+fnkl.kernel.gmail.com@...nel.org>
To: Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>, 
 Alyssa Rosenzweig <alyssa@...enzweig.io>, Vinod Koul <vkoul@...nel.org>, 
 Martin Povišer <povik+lin@...ebit.org>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Sasha Finkelstein <fnkl.kernel@...il.com>
Subject: [PATCH] dmaengine: apple-admac: Avoid accessing registers in probe

From: Sasha Finkelstein <fnkl.kernel@...il.com>

The ADMAC attached to the AOP has complex power sequencing, and is
power gated when the probe callback runs. Move the register reads
to other functions, where we can guarantee that the hardware is
switched on.

Fixes: 568aa6dd641f ("dmaengine: apple-admac: Allocate cache SRAM to channels")
Signed-off-by: Sasha Finkelstein <fnkl.kernel@...il.com>
---
 drivers/dma/apple-admac.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/apple-admac.c b/drivers/dma/apple-admac.c
index 9588773dd2eb670a2f6115fdaef39a0e88248015..037ec38730cf980eee11ebb8ec17be7623879cf8 100644
--- a/drivers/dma/apple-admac.c
+++ b/drivers/dma/apple-admac.c
@@ -153,6 +153,8 @@ static int admac_alloc_sram_carveout(struct admac_data *ad,
 {
 	struct admac_sram *sram;
 	int i, ret = 0, nblocks;
+	ad->txcache.size = readl_relaxed(ad->base + REG_TX_SRAM_SIZE);
+	ad->rxcache.size = readl_relaxed(ad->base + REG_RX_SRAM_SIZE);
 
 	if (dir == DMA_MEM_TO_DEV)
 		sram = &ad->txcache;
@@ -912,12 +914,7 @@ static int admac_probe(struct platform_device *pdev)
 		goto free_irq;
 	}
 
-	ad->txcache.size = readl_relaxed(ad->base + REG_TX_SRAM_SIZE);
-	ad->rxcache.size = readl_relaxed(ad->base + REG_RX_SRAM_SIZE);
-
 	dev_info(&pdev->dev, "Audio DMA Controller\n");
-	dev_info(&pdev->dev, "imprint %x TX cache %u RX cache %u\n",
-		 readl_relaxed(ad->base + REG_IMPRINT), ad->txcache.size, ad->rxcache.size);
 
 	return 0;
 

---
base-commit: 9f16d5e6f220661f73b36a4be1b21575651d8833
change-id: 20241124-admac-power-7f32c2a1850a