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SubjectRe: [PATCH v13 11/15] mtd: spi-nor: core: perform a Soft Reset on shutdown
On 30/09/20 07:32AM, Tudor.Ambarus@microchip.com wrote:
> On 9/29/20 4:08 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > On 16/09/20 06:14PM, Pratyush Yadav wrote:
> >> Perform a Soft Reset on shutdown on flashes that support it so that the
> >> flash can be reset to its initial state and any configurations made by
> >> spi-nor (given that they're only done in volatile registers) will be
> >> reset. This will hand back the flash in pristine state for any further
> >> operations on it.
> >>
> >> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> >> ---
> >> drivers/mtd/spi-nor/core.c | 41 +++++++++++++++++++++++++++++++++++++
> >> include/linux/mtd/spi-nor.h | 2 ++
> >> 2 files changed, 43 insertions(+)
> >>
> >> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >> index 6ee93544d72f..853dfa02f0de 100644
> >> --- a/drivers/mtd/spi-nor/core.c
> >> +++ b/drivers/mtd/spi-nor/core.c
> >> @@ -40,6 +40,9 @@
> >>
> >> #define SPI_NOR_MAX_ADDR_WIDTH 4
> >>
> >> +#define SPI_NOR_SRST_SLEEP_MIN 200
> >> +#define SPI_NOR_SRST_SLEEP_MAX 400
> >> +
> >> /**
> >> * spi_nor_get_cmd_ext() - Get the command opcode extension based on the
> >> * extension type.
> >> @@ -3174,6 +3177,41 @@ static int spi_nor_init(struct spi_nor *nor)
> >> return 0;
> >> }
> >>
> >> +static void spi_nor_soft_reset(struct spi_nor *nor)
> >> +{
> >> + struct spi_mem_op op;
> >> + int ret;
> >> +
> >> + op = (struct spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRSTEN, 8),
>
> can we avoid the cast?

No. The compiler complains about "expected expression before '{' token".
We can avoid it if the assignment is with the declaration but then we
can't re-use the variable op for the second command.

I like the cast better than using separate variables for the two (or
more in other cases) commands we execute.

> >
> > The buswidth used here should be 1 instead of 8. It makes no difference
> > in practice because the call to spi_nor_spimem_setup_op() immediately
> > after will over-write it to the correct value anyway, but let's follow
> > the style followed throughout the rest of the codebase. Will fix in the
> > next version.
>
> or you can just set the buswidth to 0 so that the reader rises his eyebrow
> and search for where it is updated. If you like it better you'll have to change
> throughout the entire code base, maybe in 4/15 where setup_op is introduced.

Ok. Will change it.

> >
> >> + SPI_MEM_OP_NO_DUMMY,
> >> + SPI_MEM_OP_NO_ADDR,
> >> + SPI_MEM_OP_NO_DATA);
> >> + spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
>
> Still not a big fan of this, but we can update the op init later on. How
> about some new lines around spi_nor_spimem_setup_op()? First time I read
> the code I haven't seen it.

Ok.

> >> + ret = spi_mem_exec_op(nor->spimem, &op);
> >> + if (ret) {
> >> + dev_warn(nor->dev, "Software reset failed: %d\n", ret);
> >> + return;
> >> + }
> >> +
> >> + op = (struct spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRST, 8),
> >
> > Same here.
> >
> >> + SPI_MEM_OP_NO_DUMMY,
> >> + SPI_MEM_OP_NO_ADDR,
> >> + SPI_MEM_OP_NO_DATA);
> >> + spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> >> + ret = spi_mem_exec_op(nor->spimem, &op);
> >> + if (ret) {
> >> + dev_warn(nor->dev, "Software reset failed: %d\n", ret);
> >> + return;
> >> + }
> >> +
> >> + /*
> >> + * Software Reset is not instant, and the delay varies from flash to
> >> + * flash. Looking at a few flashes, most range somewhere below 100
> >> + * microseconds. So, sleep for a range of 200-400 us.
> >> + */
> >> + usleep_range(SPI_NOR_SRST_SLEEP_MIN, SPI_NOR_SRST_SLEEP_MAX);
> >> +}
> >> +
> >> /* mtd resume handler */
> >> static void spi_nor_resume(struct mtd_info *mtd)
> >> {

--
Regards,
Pratyush Yadav
Texas Instruments India

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