linux-kernel - [PATCH v2 1/5] dmaengine: dw-edma: Fix the ch

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Date:   Mon,  2 Oct 2023 15:17:45 +0200
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     Cai Huoqing <cai.huoqing@...ux.dev>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Kory Maincent <kory.maincent@...tlin.com>
Subject: [PATCH v2 1/5] dmaengine: dw-edma: Fix the ch_count hdma callback

From: Kory Maincent <kory.maincent@...tlin.com>

The current check of ch_en enabled to know the maximum number of available
hardware channels is wrong as it check the number of ch_en register set
but all of them are unset at probe. This register is set at the
dw_hdma_v0_core_start function which is run lately before a DMA transfer.

The HDMA IP have no way to know the number of hardware channels available
like the eDMA IP, then let set it to maximum channels and let the platform
set the right number of channels.

Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
---

See the following thread mail that talk about this issue:
https://lore.kernel.org/lkml/20230607095832.6d6b1a73@kmaincent-XPS-13-7390/

Changes in v2:
- Add comment
---
 drivers/dma/dw-edma/dw-hdma-v0-core.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
index 00b735a0202a..3e78d4fd3955 100644
--- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
@@ -65,18 +65,11 @@ static void dw_hdma_v0_core_off(struct dw_edma *dw)
 
 static u16 dw_hdma_v0_core_ch_count(struct dw_edma *dw, enum dw_edma_dir dir)
 {
-	u32 num_ch = 0;
-	int id;
-
-	for (id = 0; id < HDMA_V0_MAX_NR_CH; id++) {
-		if (GET_CH_32(dw, id, dir, ch_en) & BIT(0))
-			num_ch++;
-	}
-
-	if (num_ch > HDMA_V0_MAX_NR_CH)
-		num_ch = HDMA_V0_MAX_NR_CH;
-
-	return (u16)num_ch;
+	/* The HDMA IP have no way to know the number of hardware channels
+	 * available, we set it to maximum channels and let the platform
+	 * set the right number of channels.
+	 */
+	return HDMA_V0_MAX_NR_CH;
 }
 
 static enum dma_status dw_hdma_v0_core_ch_status(struct dw_edma_chan *chan)
-- 
2.25.1