linux-kernel - RE: [PATCH 3/3] mtd: spi-nor: sf: Add clear flag status register support

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Date:	Thu, 20 Aug 2015 03:06:31 +0000
From:	Hou Zhiqiang <B48286@...escale.com>
To:	Jagan Teki <jteki@...nedev.com>
CC:	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"Hu Vincent" <Mingkai.Hu@...escale.com>,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] mtd: spi-nor: sf: Add clear flag status register
 support

Hello Jagan,

> -----Original Message-----
> From: Jagan Teki [mailto:jteki@...nedev.com]
> Sent: 2015年8月20日 1:49
> To: Hou Zhiqiang-B48286
> Cc: linux-mtd@...ts.infradead.org; Hu Mingkai-B21284; Brian Norris; David
> Woodhouse; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 3/3] mtd: spi-nor: sf: Add clear flag status register
> support
> 
> Hi Zhiqiang,
> 
> On 19 August 2015 at 17:42, Hou Zhiqiang <B48286@...escale.com> wrote:
> > Hi Jagan,
> >
> >> -----Original Message-----
> >> From: Jagan Teki [mailto:jteki@...nedev.com]
> >> Sent: 2015年8月19日 17:57
> >> To: linux-mtd@...ts.infradead.org
> >> Cc: linux-kernel@...r.kernel.org; Jagan Teki; Hou Zhiqiang-B48286; Hu
> >> Mingkai-B21284; David Woodhouse; Brian Norris
> >> Subject: [PATCH 3/3] mtd: spi-nor: sf: Add clear flag status register
> >> support
> >>
> >> The clear flag status register operation was required by Micron
> >> SPI-NOR chips, which support FSR. And if an error bit of FSR have
> >> been set like protection, voltage, erase, and program, it must be
> >> cleared by the clear FSR operation.
> >>
> >> Signed-off-by: Jagan Teki <jteki@...nedev.com>
> >> Cc: Hou Zhiqiang <B48286@...escale.com>
> >> Cc: Mingkai.Hu <Mingkai.Hu@...escale.com>
> >> Cc: David Woodhouse <dwmw2@...radead.org>
> >> Cc: Brian Norris <computersforpeace@...il.com>
> >> ---
> >>  drivers/mtd/spi-nor/spi-nor.c | 35 +++++++++++++++++++++++++++++++---
> -
> >>  include/linux/mtd/spi-nor.h   |  9 +++++++++
> >>  2 files changed, 40 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-
> >> nor.c index f954d03..c5c472d5 100644
> >> --- a/drivers/mtd/spi-nor/spi-nor.c
> >> +++ b/drivers/mtd/spi-nor/spi-nor.c
> >> @@ -100,6 +100,28 @@ static int read_fsr(struct spi_nor *nor)  }
> >>
> >>  /*
> >> + * Read the clear flag status register.
> >> + * The clear flag status register operation was required by Micron
> >> + * SPI-NOR chips, which support FSR. And if an error bit of FSR
> >> + * have been set like protection, voltage, erase, and program,
> >> + * it must be cleared by the clear FSR operation.
> >> + * Returns zero for FSR bits cleared and negative if error occurred.
> >> + */
> >> +static int read_cfsr(struct spi_nor *nor) {
> >> +     int ret;
> >> +     u8 val;
> >> +
> >> +     ret = nor->read_reg(nor, SPINOR_OP_RDCFSR, &val, 1);
> >
> > There should be a write_reg instead of read_reg.
> > There isn’t a register named CFSR, and the command SPINOR_OP_RDCFSR is
> > used to clear the FSR, another words reset FSR to default value.
> 
> Yes, SPINOR_OP_RDCFSR is clear flag status register, for clearing errors
> bits on fsr we need to read cfsr once.
> 

Sorry, I'm not clear for this operation. Please correct me if I'm wrong.
As far as I understand, this command is used to reset the FSR. Does a value
Will be read back? And there is not the register CFSR, so I don't know which
register will be read by SPINOR_OP_RDCFSR?

> >
> >> +     if (ret < 0) {
> >> +             pr_err("error %d reading CFSR\n", ret);
> >> +             return ret;
> >> +     }
> >> +
> >> +     return val;
> >> +}
> >> +
> >> +/*

Thanks,
Zhiqiang