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SubjectRe: [PATCH V2 2/2] mtd: rawnand: qcom: set BAM mode only if not set already
Hi Sivaprakash,

Sivaprakash Murugesan <sivaprak@codeaurora.org> wrote on Tue, 9 Jun
2020 16:40:56 +0530:

> 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);
> }

Does this currently produces an issue at runtime?

If yes, you should have a Fixes/CC: stable pair of tags.

Also, what is BAM mode? Please tell us in the commit log.

Thanks,
Miquèl

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