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SubjectRe: [EXT] Re: [PATCH nvmem 1/1] nvmem: imx: correct the fuse word index
Hi,

On Fri, 5 Jul 2019 02:46:32 +0000 Andy Duan wrote:
> From: Andy Duan Sent: Friday, July 5, 2019 12:08 AM
> > From: Lothar Waßmann <LW@KARO-electronics.de> Sent: Thursday, July 4,
> > 2019 11:46 PM
> > > Hi,
> > >
> > > On Thu, 4 Jul 2019 22:20:15 +0800 fugang.duan@nxp.com wrote:
> > > > From: Fugang Duan <fugang.duan@nxp.com>
> > > >
> > > > iMX8 fuse word index represent as one 4-bytes word, it should not be
> > > > divided by 4.
> > > >
> > > > Exp:
> > > > - MAC0 address layout in fuse:
> > > > offset 708: MAC[3] MAC[2] MAC[1] MAC[0]
> > > > offset 709: XX xx MAC[5] MAC[4]
> > > >
> > > > Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
> > > > ---
> > > > drivers/nvmem/imx-ocotp-scu.c | 6 +++---
> > > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/nvmem/imx-ocotp-scu.c
> > > > b/drivers/nvmem/imx-ocotp-scu.c index d9dc482..be2f5f0 100644
> > > > --- a/drivers/nvmem/imx-ocotp-scu.c
> > > > +++ b/drivers/nvmem/imx-ocotp-scu.c
> > > > @@ -71,8 +71,8 @@ static int imx_scu_ocotp_read(void *context,
> > > > unsigned
> > > int offset,
> > > > void *p;
> > > > int i, ret;
> > > >
> > > > - index = offset >> 2;
> > > > - num_bytes = round_up((offset % 4) + bytes, 4);
> > > > + index = offset;
> > > > + num_bytes = round_up(bytes, 4);
> > > > count = num_bytes >> 2;
> > > >
> > > > if (count > (priv->data->nregs - index)) @@ -100,7 +100,7 @@
> > > > static int imx_scu_ocotp_read(void *context, unsigned int offset,
> > > > buf++;
> > > > }
> > > >
> > > > - memcpy(val, (u8 *)p + offset % 4, bytes);
> > > > + memcpy(val, (u8 *)p, bytes);
> > > >
> > > > kfree(p);
> > > >
> > > With these changes you could use the 'val' pointer directly as the
> > > destination for ocotp_read() without need for an intermediate buffer.
> > >
> > >
> > > Lothar Waßmann
> >
> > You are right, in fact, we can remove "p" and "buf" pointer.
> > Thanks for your review, I will send out the V2.
>
> Hi Lothar,
>
> It still need intermediate buffer to read out n words (n * 4 bytes) from eFuse.
> Because 'val' buffer size is real count parsed from DT, which is not an integer multiple of 4.
>
> For example, cell->bytes is parsed from "reg" property and it is real count like 6.
> fec_mac0: mac@2c4 {
> reg = <0x2c4 6>;
> };
>
> So we have to use intermediate buffer here.
>
val is a u32 pointer, so legally it cannot point to any buffer whose
size is not divisible by four!


Lothar Waßmann

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