Re: [PATCH V3] Add support for flag status register on Micron chips.

Marek Vasut
2014-04-25T02:43:03Z

On Friday, April 25, 2014 at 03:34:36 AM, Huang Shijie wrote:
> On Tue, Apr 22, 2014 at 09:03:16AM -0500, Graham Moore wrote:
> > Some new Micron flash chips require reading the flag
> > status register to determine when operations have completed.
> >
> > Furthermore, chips with multi-die stacks of the 65nm 256Mb QSPI also
> > require reading the status register before reading the flag status
> > register.
> >
> > This patch adds support for the flag status register in the n25q512ax3
> > and n25q00 Micron QSPI flash chips.
> >
> > Signed-off-by: Graham Moore <grmoore@altera.com>
> > ---
> > V3:
> > Rebase to l2-mtd spinor branch.
> > V2:
> > Remove leading underscore in function names.
> > Remove type cast in dev_err call and use the proper format
> > specifier instead.
> > ---
> >
> > drivers/mtd/spi-nor/spi-nor.c | 51
> > +++++++++++++++++++++++++++++++++++++++++ include/linux/mtd/spi-nor.h
> > | 4 ++++
> > 2 files changed, 55 insertions(+)
> >
> > diff --git a/drivers/mtd/spi-nor/spi-nor.c
> > b/drivers/mtd/spi-nor/spi-nor.c index d6f44d5..24b84d8 100644
> > --- a/drivers/mtd/spi-nor/spi-nor.c
> > +++ b/drivers/mtd/spi-nor/spi-nor.c
> > @@ -48,6 +48,25 @@ static int read_sr(struct spi_nor *nor)
> >
> > }
> >
> > /*
> >
> > + * Read the flag status register, returning its value in the location
> > + * Return the status register value.
> > + * Returns negative if error occurred.
> > + */
> > +static int read_fsr(struct spi_nor *nor)
> > +{
> > + int ret;
> > + u8 val;
> > +
> > + ret = nor->read_reg(nor, SPINOR_OP_RDFSR, &val, 1);
> > + if (ret < 0) {
> > + pr_err("error %d reading FSR\n", ret);
> > + return ret;
> > + }
> > +
> > + return val;
> > +}
> > +
> > +/*
> >
> > * Read configuration register, returning its value in the
> > * location. Return the configuration register value.
> > * Returns negative if error occured.
> >
> > @@ -165,6 +184,32 @@ static int spi_nor_wait_till_ready(struct spi_nor
> > *nor)
> >
> > return -ETIMEDOUT;
> >
> > }
> >
> > +static int spi_nor_wait_till_fsr_ready(struct spi_nor *nor)
> > +{
> > + unsigned long deadline;
> > + int sr;
> > + int fsr;
> > +
> > + deadline = jiffies + MAX_READY_WAIT_JIFFIES;
> > +
> > + do {
> > + cond_resched();
> > +
> > + sr = read_sr(nor);
> > + if (sr < 0)
> > + break;
> > + else if (!(sr & SR_WIP)) {
> > + fsr = read_fsr(nor);
> > + if (fsr < 0)
> > + break;
> > + if (fsr & FSR_READY)
> > + return 0;
> > + }
> > + } while (!time_after_eq(jiffies, deadline));
> > +
> > + return -ETIMEDOUT;
> > +}
> > +
> >
> > /*
> >
> > * Service routine to read status register until ready, or timeout
> > occurs. * Returns non-zero if error.
> >
> > @@ -402,6 +447,7 @@ struct flash_info {
> >
> > #define SECT_4K_PMC 0x10 /* SPINOR_OP_BE_4K_PMC works
uniformly */
> > #define SPI_NOR_DUAL_READ 0x20 /* Flash supports Dual Read */
> > #define SPI_NOR_QUAD_READ 0x40 /* Flash supports Quad Read */
> >
> > +#define USE_FSR 0x80 /* use flag status register */
> >
> > };
> >
> > #define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags) \
> >
> > @@ -488,6 +534,8 @@ const struct spi_device_id spi_nor_ids[] = {
> >
> > { "n25q128a13", INFO(0x20ba18, 0, 64 * 1024, 256, 0) },
> > { "n25q256a", INFO(0x20ba19, 0, 64 * 1024, 512, SECT_4K) },
> > { "n25q512a", INFO(0x20bb20, 0, 64 * 1024, 1024, SECT_4K) },
> >
> > + { "n25q512ax3", INFO(0x20ba20, 0, 64 * 1024, 1024, USE_FSR) },
> > + { "n25q00", INFO(0x20ba21, 0, 64 * 1024, 2048, USE_FSR) },
> >
> > /* PMC */
> > { "pm25lv512", INFO(0, 0, 32 * 1024, 2, SECT_4K_PMC) },
> >
> > @@ -965,6 +1013,9 @@ int spi_nor_scan(struct spi_nor *nor, const struct
> > spi_device_id *id,
> >
> > else
> >
> > mtd->_write = spi_nor_write;
> >
> > + if (info->flags & USE_FSR)
> > + nor->wait_till_ready = spi_nor_wait_till_fsr_ready;
> > +
>
> the drivers may fills this hook itself, so the code should like this:
> --------------------------------------------------
> if ((info->flags & USE_FSR) &&
> nor->wait_till_ready == spi_nor_wait_till_fsr_ready)
> nor->wait_till_ready = spi_nor_wait_till_fsr_ready;
> --------------------------------------------------

I sense a misdesign of the SPI NOR subsystem here. The subsystem and the driver
compete for a function pointer here ? I guess one should have precedence in some
way then ... and also, they should be two different pointers, where the
subsystem decides which to use.