Re: [PATCH v4 1/2] mtd: spi-nor: split spi_nor_spimem_xfer_data()

[<Tudor.Ambarus@xxxxxxxxxxxxx>]

Hi, Sergei,

Looks good. Just a nit below that I can fix it when applying. Let me know if 
you're ok with the change.

On Monday, January 27, 2020 10:28:05 PM EET Sergei Shtylyov wrote:
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> 
> spi_nor_spimem_xfer_data() being a helper function for the data reads/
> writes contains 3 fragments that depend on the data direction; and I'm
> going to add another one to call the SPI dirmap API...
> I think this function should be split so that the common fragments are
> put into 2 functions, spi_nor_spimem_bounce() and spi_nor_spimem_exec_op()
> called from spi_nor_spimem_{read|write}_data(), and the data direction
> dependent bits moved back into those read/write functions -- that way we
> would be able to avoid *goto*s otherwise needed in the next patch adding
> the  SPI dirmap support...
> 
> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
> 
> ---
> Changes in version 4:
> - new patch.
> 
>  drivers/mtd/spi-nor/spi-nor.c |   91
> +++++++++++++++++++++++------------------- 1 file changed, 51
> insertions(+), 40 deletions(-)
> 
> Index: linux/drivers/mtd/spi-nor/spi-nor.c
> ===================================================================
> --- linux.orig/drivers/mtd/spi-nor/spi-nor.c
> +++ linux/drivers/mtd/spi-nor/spi-nor.c
> @@ -246,55 +246,45 @@ struct flash_info {
>  #define JEDEC_MFR(info)        ((info)->id[0])
> 
>  /**
> - * spi_nor_spimem_xfer_data() - helper function to read/write data to
> - *                              flash's memory region
> + * spi_nor_spimem_bounce() - check if a bounce buffer is needed for the
> data + *                           transfer
>   * @nor:        pointer to 'struct spi_nor'
>   * @op:         pointer to 'struct spi_mem_op' template for transfer
>   *
> - * Return: number of bytes transferred on success, -errno otherwise
> + * If we have to use the bounce buffer, the data field in @op will be
> updated. + *
> + * Return: true if the bounce buffer is needed, false if not
>   */
> -static ssize_t spi_nor_spimem_xfer_data(struct spi_nor *nor,
> -                                       struct spi_mem_op *op)
> +static bool spi_nor_spimem_bounce(struct spi_nor *nor, struct spi_mem_op
> *op) {
> -       bool usebouncebuf = false;
> -       void *rdbuf = NULL;
> -       const void *buf;
> -       int ret;
> -
> -       if (op->data.dir == SPI_MEM_DATA_IN)
> -               buf = op->data.buf.in;
> -       else
> -               buf = op->data.buf.out;
> -
> -       if (object_is_on_stack(buf) || !virt_addr_valid(buf))
> -               usebouncebuf = true;
> -
> -       if (usebouncebuf) {
> +       /* op->data.buf.in occupies the same memory as op->data.buf.out */
> +       if (object_is_on_stack(op->data.buf.in) ||
> +           !virt_addr_valid(op->data.buf.in)) {
>                 if (op->data.nbytes > nor->bouncebuf_size)
>                         op->data.nbytes = nor->bouncebuf_size;
> -
> -               if (op->data.dir == SPI_MEM_DATA_IN) {
> -                       rdbuf = op->data.buf.in;
> -                       op->data.buf.in = nor->bouncebuf;
> -               } else {
> -                       op->data.buf.out = nor->bouncebuf;
> -                       memcpy(nor->bouncebuf, buf,
> -                              op->data.nbytes);
> -               }
> +               op->data.buf.in = nor->bouncebuf;
> +               return true;
>         }
> 
> -       ret = spi_mem_adjust_op_size(nor->spimem, op);
> -       if (ret)
> -               return ret;
> -
> -       ret = spi_mem_exec_op(nor->spimem, op);
> -       if (ret)
> -               return ret;
> +       return false;
> +}
> +
> +/**
> + * spi_nor_spimem_exec_op() - execute a memory operation
> + * @nor:        pointer to 'struct spi_nor'
> + * @op:         pointer to 'struct spi_mem_op' template for transfer
> + *
> + * Return: 0 on success, -error otherwise.
> + */
> +static int spi_nor_spimem_exec_op(struct spi_nor *nor, struct spi_mem_op
> *op) +{
> +       int error;
> 
> -       if (usebouncebuf && op->data.dir == SPI_MEM_DATA_IN)
> -               memcpy(rdbuf, nor->bouncebuf, op->data.nbytes);
> +       error = spi_mem_adjust_op_size(nor->spimem, op);
> +       if (error)
> +               return error;
> 
> -       return op->data.nbytes;
> +       return spi_mem_exec_op(nor->spimem, op);
>  }
> 
>  /**
> @@ -315,6 +305,8 @@ static ssize_t spi_nor_spimem_read_data(
>                            SPI_MEM_OP_ADDR(nor->addr_width, from, 1),
>                            SPI_MEM_OP_DUMMY(nor->read_dummy, 1),
>                            SPI_MEM_OP_DATA_IN(len, buf, 1));
> +       bool usebouncebuf;
> +       int error;
> 
>         /* get transfer protocols. */
>         op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->read_proto);
> @@ -325,7 +317,16 @@ static ssize_t spi_nor_spimem_read_data(
>         /* convert the dummy cycles to the number of bytes */
>         op.dummy.nbytes = (nor->read_dummy * op.dummy.buswidth) / 8;
> 
> -       return spi_nor_spimem_xfer_data(nor, &op);
> +       usebouncebuf = spi_nor_spimem_bounce(nor, &op);
> +
> +       error = spi_nor_spimem_exec_op(nor, &op);
> +       if (error)
> +               return error;
> +
> +       if (usebouncebuf)
> +               memcpy(buf, op.data.buf.in, op.data.nbytes);
> +
> +       return op.data.nbytes;
>  }
> 
>  /**
> @@ -364,6 +365,8 @@ static ssize_t spi_nor_spimem_write_data
>                            SPI_MEM_OP_ADDR(nor->addr_width, to, 1),
>                            SPI_MEM_OP_NO_DUMMY,
>                            SPI_MEM_OP_DATA_OUT(len, buf, 1));
> +       bool usebouncebuf;
> +       int error;
> 
>         op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->write_proto);
> op.addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->write_proto); @@
> -372,7 +375,15 @@ static ssize_t spi_nor_spimem_write_data
>         if (nor->program_opcode == SPINOR_OP_AAI_WP &&
> nor->sst_write_second) op.addr.nbytes = 0;
> 
> -       return spi_nor_spimem_xfer_data(nor, &op);
> +       usebouncebuf = spi_nor_spimem_bounce(nor, &op);
> +       if (usebouncebuf)
> +               memcpy(nor->bouncebuf, buf, op.data.nbytes);

How about memcpy(nor->bouncebuf, buf, len); instead?

spi_nor_spimem_bounce() does not modify op.data.nbytes. Using len is more 
straight forward than op.data.bytes because the reader doesn't have to verify 
if length was updated in spi_nor_spimem_bounce() or not.

Cheers,
ta




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