linux-kernel - Re: spi: imx: Increase imx51 ecspi burst length fails on imx6dl and imx8mm

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Message-ID: <c7a38307ac74a973e26ac820a0b98773262720bd.camel@bigler.one>
Date:   Sun, 26 Nov 2023 14:19:56 +0100
From:   Benjamin Bigler <benjamin@...ler.one>
To:     benjamin@...ler.one
Cc:     broonie@...nel.org, francesco@...cini.it,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        linux@...ler.io, regressions@...ts.linux.dev,
        stefan.moring@...hnolution.nl
Subject: Re: spi: imx: Increase imx51 ecspi burst length fails on imx6dl and
 imx8mm

Hi

I did some debugging and I think the problem is that in this case bits_per_word is 8. So in
spi_imx_dma_configure the buswidth is set to DMA_SLAVE_BUSWIDTH_1_BYTE. But in
mx51_ecspi_prepare_transfer the BURST_LENGTH is now set to (spi_imx->count * spi_imx->bits_per_word
- 1)
before 15a6af94a2779d5dfb42ee4bfac858ea8e964a3f it was (spi_imx->bits_per_word - 1). Now the spi
transmits 4 byte per byte except for the first word. I added the following patch and it worked again

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 498e35c8db2c..f514966e2ada 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -659,11 +659,22 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx,
 		ctrl |= (spi_imx->target_burst * 8 - 1)
 			<< MX51_ECSPI_CTRL_BL_OFFSET;
 	else {
-		if (spi_imx->count >= 512)
-			ctrl |= 0xFFF << MX51_ECSPI_CTRL_BL_OFFSET;
-		else
-			ctrl |= (spi_imx->count * spi_imx->bits_per_word - 1)
+		if (spi_imx->usedma)
+			ctrl |= (spi_imx->bits_per_word *
+					 spi_imx_bytes_per_word(
+						 spi_imx->bits_per_word) -
+				 1)
 				<< MX51_ECSPI_CTRL_BL_OFFSET;
+		else {
+			if (spi_imx->count >= MX51_ECSPI_CTRL_MAX_BURST)
+				ctrl |= (MX51_ECSPI_CTRL_MAX_BURST - 1)
+					<< MX51_ECSPI_CTRL_BL_OFFSET;
+			else
+				ctrl |= (spi_imx->count *
+						 spi_imx->bits_per_word -
+					 1)
+					<< MX51_ECSPI_CTRL_BL_OFFSET;
+		}
 	}
 
 	/* set clock speed */

Best regards,
Benjamin Bigler