Re: [PATCH v2 03/11] spi: spi-mem: allow specifying whether an op is DTR or not

Boris Brezillon
2020-02-27T16:36:36Z

On Wed, 26 Feb 2020 15:06:55 +0530
Pratyush Yadav <p.yadav@ti.com> wrote:

> Each phase is given a separate 'is_dtr' field so mixed protocols like
> 4S-4D-4D can be supported.
>
> Also add the mode bits SPI_RX_DTR and SPI_TX_DTR so controllers can
> specify whether they support DTR modes or not.
>
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> ---
> drivers/spi/spi-mem.c | 23 +++++++++++++++++++++++
> include/linux/spi/spi-mem.h | 8 ++++++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index e5a46f0eb93b..cb13e0878b95 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -99,6 +99,16 @@ void spi_controller_dma_unmap_mem_op_data(struct spi_controller *ctlr,
> }
> EXPORT_SYMBOL_GPL(spi_controller_dma_unmap_mem_op_data);
>
> +static int spi_check_dtr_req(struct spi_mem *mem, bool tx)
> +{
> + u32 mode = mem->spi->mode;
> +
> + if ((tx && (mode & SPI_TX_DTR)) || (!tx && (mode & SPI_RX_DTR)))
> + return 0;
> +
> + return -ENOTSUPP;
> +}
> +
> static int spi_check_buswidth_req(struct spi_mem *mem, u8 buswidth, bool tx)
> {
> u32 mode = mem->spi->mode;
> @@ -154,6 +164,19 @@ bool spi_mem_default_supports_op(struct spi_mem *mem,
> op->data.dir == SPI_MEM_DATA_OUT))
> return false;
>
> + if (op->cmd.is_dtr && spi_check_dtr_req(mem, true))
> + return false;
> +
> + if (op->addr.is_dtr && spi_check_dtr_req(mem, true))
> + return false;
> +
> + if (op->dummy.is_dtr && spi_check_dtr_req(mem, true))
> + return false;
> +
> + if (op->data.dir != SPI_MEM_NO_DATA && op->data.is_dtr &&
> + spi_check_dtr_req(mem, op->data.dir == SPI_MEM_DATA_OUT))
> + return false;
> +

Not all controllers use spi_mem_default_supports_op(). Those should be
patched to reject DTR ops too.

> return true;
> }
> EXPORT_SYMBOL_GPL(spi_mem_default_supports_op);
> diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> index af9ff2f0f1b2..4669082b4e3b 100644
> --- a/include/linux/spi/spi-mem.h
> +++ b/include/linux/spi/spi-mem.h
> @@ -71,6 +71,7 @@ enum spi_mem_data_dir {
> * struct spi_mem_op - describes a SPI memory operation
> * @cmd.buswidth: number of IO lines used to transmit the command
> * @cmd.opcode: operation opcode
> + * @cmd.is_dtr: whether the command opcode should be sent in DTR mode or not
> * @addr.nbytes: number of address bytes to send. Can be zero if the operation
> * does not need to send an address
> * @addr.buswidth: number of IO lines used to transmit the address cycles
> @@ -78,10 +79,13 @@ enum spi_mem_data_dir {
> * Note that only @addr.nbytes are taken into account in this
> * address value, so users should make sure the value fits in the
> * assigned number of bytes.
> + * @addr.is_dtr: whether the address should be sent in DTR mode or not
> * @dummy.nbytes: number of dummy bytes to send after an opcode or address. Can
> * be zero if the operation does not require dummy bytes
> * @dummy.buswidth: number of IO lanes used to transmit the dummy bytes
> + * @dummy.is_dtr: whether the dummy bytes should be sent in DTR mode or not
> * @data.buswidth: number of IO lanes used to send/receive the data
> + * @data.is_dtr: whether the data should be sent in DTR mode or not
> * @data.dir: direction of the transfer
> * @data.nbytes: number of data bytes to send/receive. Can be zero if the
> * operation does not involve transferring data
> @@ -92,21 +96,25 @@ struct spi_mem_op {
> struct {
> u8 buswidth;
> u8 opcode;
> + bool is_dtr;

Hm, maybe use a bitfield here so we can pack other fields if needed.
Also not convince the 'is_' prefix is useful.

u8 dtr : 1;

> } cmd;
>
> struct {
> u8 nbytes;
> u8 buswidth;

Maybe move the dtr field here so the compiler can pack things instead of
adding extra padding for the u64 alignment.

u8 dtr : 1;

> u64 val;
> + bool is_dtr;
> } addr;
>
> struct {
> u8 nbytes;
> u8 buswidth;
> + bool is_dtr;
> } dummy;
>
> struct {
> u8 buswidth;
> + bool is_dtr;
> enum spi_mem_data_dir dir;
> unsigned int nbytes;
> union {