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From: Sivaprakash Murugesan <sivaprak@codeaurora.org>
To: miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
	peter.ujfalusi@ti.com, sivaprak@codeaurora.org,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH V2 2/2] mtd: rawnand: qcom: set BAM mode only if not set already
Date: Tue,  9 Jun 2020 16:40:56 +0530	[thread overview]
Message-ID: <1591701056-3944-3-git-send-email-sivaprak@codeaurora.org> (raw)
In-Reply-To: <1591701056-3944-1-git-send-email-sivaprak@codeaurora.org>

BAM mode is set by writing BAM_MODE_EN bit on NAND_CTRL register.
NAND_CTRL is an operational register and in BAM mode operational
registers are read only.

So, before writing into NAND_CTRL register check if BAM mode is already
enabled by bootloader, and set BAM mode only if it is not set already.

Signed-off-by: Sivaprakash Murugesan <sivaprak@codeaurora.org>
---
 drivers/mtd/nand/raw/qcom_nandc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
index e0afa2c..7740059 100644
--- a/drivers/mtd/nand/raw/qcom_nandc.c
+++ b/drivers/mtd/nand/raw/qcom_nandc.c
@@ -2779,7 +2779,14 @@ static int qcom_nandc_setup(struct qcom_nand_controller *nandc)
 	/* enable ADM or BAM DMA */
 	if (nandc->props->is_bam) {
 		nand_ctrl = nandc_read(nandc, NAND_CTRL);
-		nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
+		/* NAND_CTRL is an operational registers, and CPU
+		 * access to operational registers are read only
+		 * in BAM mode. So update the NAND_CTRL register
+		 * only if it is not in BAM mode. In most cases BAM
+		 * mode will be enabled in bootloader
+		 */
+		if (!(nand_ctrl | BAM_MODE_EN))
+			nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
 	} else {
 		nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
 	}
-- 
2.7.4


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WARNING: multiple messages have this Message-ID (diff)
From: Sivaprakash Murugesan <sivaprak@codeaurora.org>
To: miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
	peter.ujfalusi@ti.com, sivaprak@codeaurora.org,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH V2 2/2] mtd: rawnand: qcom: set BAM mode only if not set already
Date: Tue,  9 Jun 2020 16:40:56 +0530	[thread overview]
Message-ID: <1591701056-3944-3-git-send-email-sivaprak@codeaurora.org> (raw)
In-Reply-To: <1591701056-3944-1-git-send-email-sivaprak@codeaurora.org>

BAM mode is set by writing BAM_MODE_EN bit on NAND_CTRL register.
NAND_CTRL is an operational register and in BAM mode operational
registers are read only.

So, before writing into NAND_CTRL register check if BAM mode is already
enabled by bootloader, and set BAM mode only if it is not set already.

Signed-off-by: Sivaprakash Murugesan <sivaprak@codeaurora.org>
---
 drivers/mtd/nand/raw/qcom_nandc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
index e0afa2c..7740059 100644
--- a/drivers/mtd/nand/raw/qcom_nandc.c
+++ b/drivers/mtd/nand/raw/qcom_nandc.c
@@ -2779,7 +2779,14 @@ static int qcom_nandc_setup(struct qcom_nand_controller *nandc)
 	/* enable ADM or BAM DMA */
 	if (nandc->props->is_bam) {
 		nand_ctrl = nandc_read(nandc, NAND_CTRL);
-		nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
+		/* NAND_CTRL is an operational registers, and CPU
+		 * access to operational registers are read only
+		 * in BAM mode. So update the NAND_CTRL register
+		 * only if it is not in BAM mode. In most cases BAM
+		 * mode will be enabled in bootloader
+		 */
+		if (!(nand_ctrl | BAM_MODE_EN))
+			nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
 	} else {
 		nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
 	}
-- 
2.7.4


  parent reply	other threads:[~2020-06-09 11:11 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-09 11:10 [PATCH V2 0/2] Fix issues related to register access in IPQ NAND Sivaprakash Murugesan
2020-06-09 11:10 ` Sivaprakash Murugesan
2020-06-09 11:10 ` [PATCH V2 1/2] mtd: rawnand: qcom: remove write to unavailable register Sivaprakash Murugesan
2020-06-09 11:10   ` Sivaprakash Murugesan
2020-06-09 14:02   ` Miquel Raynal
2020-06-09 14:02     ` Miquel Raynal
2020-06-11  4:30     ` Sivaprakash Murugesan
2020-06-11  4:30       ` Sivaprakash Murugesan
2020-06-09 11:10 ` Sivaprakash Murugesan [this message]
2020-06-09 11:10   ` [PATCH V2 2/2] mtd: rawnand: qcom: set BAM mode only if not set already Sivaprakash Murugesan
2020-06-09 14:03   ` Miquel Raynal
2020-06-09 14:03     ` Miquel Raynal
2020-06-11  4:27     ` Sivaprakash Murugesan
2020-06-11  4:27       ` Sivaprakash Murugesan
2020-06-11  7:13       ` Miquel Raynal
2020-06-11  7:13         ` Miquel Raynal

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