Hi Sivaprakash, Sivaprakash Murugesan <sivaprak@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx> > --- > 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 ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/