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SubjectRe: [PATCH v2 2/6] spi: cadence-quadspi: Disable the DAC for Intel LGM SoC
Hi,

On 21/10/20 10:55AM, Ramuthevar,Vadivel MuruganX wrote:
> From: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@linux.intel.com>
>
> On Intel Lightning Mountain(LGM) SoCs QSPI controller do not use
> Direct Access Controller(DAC).
>
> This patch adds a quirk to disable the Direct Access Controller
> for data transfer instead it uses indirect data transfer.
>
> Signed-off-by: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@linux.intel.com>
> ---
> drivers/spi/spi-cadence-quadspi.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
> index d7b10c46fa70..3d017b484114 100644
> --- a/drivers/spi/spi-cadence-quadspi.c
> +++ b/drivers/spi/spi-cadence-quadspi.c
> @@ -1106,6 +1106,13 @@ static void cqspi_controller_init(struct cqspi_st *cqspi)
> reg |= CQSPI_REG_CONFIG_ENB_DIR_ACC_CTRL;
> writel(reg, cqspi->iobase + CQSPI_REG_CONFIG);
>
> + /* Disable direct access controller */
> + if (!cqspi->use_direct_mode) {
> + reg = readl(cqspi->iobase + CQSPI_REG_CONFIG);
> + reg &= ~CQSPI_REG_CONFIG_ENB_DIR_ACC_CTRL;
> + writel(reg, cqspi->iobase + CQSPI_REG_CONFIG);
> + }
> +

Do you really need to disable the DAC controller? cqspi_read() and
cqspi_write() already check for cqspi->use_direct_mode and avoid using
direct mode if it is false. While I don't think it would do any harm I'm
curious what prompted you to do this instead of just setting the quirk
like cdns_qspi does.

Anyway, if you do insist on doing it, it does not make any sense to set
a bit and then unset it immediately after. The datasheet I have says
this bit resets to 1 so the block above the code you added should be
removed.

> cqspi_controller_enable(cqspi, 1);
> }
>
> @@ -1388,6 +1395,10 @@ static const struct cqspi_driver_platdata am654_ospi = {
> .quirks = CQSPI_NEEDS_WR_DELAY,
> };
>
> +static const struct cqspi_driver_platdata intel_lgm_qspi = {
> + .quirks = CQSPI_DISABLE_DAC_MODE,
> +};
> +
> static const struct of_device_id cqspi_dt_ids[] = {
> {
> .compatible = "cdns,qspi-nor",
> @@ -1403,6 +1414,7 @@ static const struct of_device_id cqspi_dt_ids[] = {
> },
> {
> .compatible = "intel,lgm-qspi",
> + .data = &intel_lgm_qspi,
> },
> { /* end of table */ }
> };

--
Regards,
Pratyush Yadav
Texas Instruments India

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