| Message ID | 1369807838-18683-2-git-send-email-rajeshwari.s@samsung.com |
|---|---|
| State | Accepted |
| Commit | bb786b84bdbcfe0474d53a54c82c5695494a6ab5 |
| Headers | show |
On Wed, May 29, 2013 at 11:40 AM, Rajeshwari Shinde <rajeshwari.s@samsung.com> wrote: > A SPI slave may take time to react to a request. For SPI flash devices > this time is defined as one bit time, or a whole byte for 'fast read' > mode. > > If the SPI slave is another CPU, then the time it takes to react may > vary. It is convenient to allow the slave device to tag the start of > the actual reply so that the host can determine when this 'preamble' > finishes and the actual message starts. > > Add a preamble flag to the available SPI flags. If supported by the > driver then it will ignore any received bytes before the preamble > on each transaction. This ensures that reliable communication with > the slave is possible. > > Signed-off-by: Simon Glass <sjg@chromium.org> > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> > --- > Changes in V2: > - None > Changes in V3: > - None. > Changes in V4: > - None. > Changes in V5: > - In commit message header changed SPI to spi. > include/spi.h | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/include/spi.h b/include/spi.h > index 3fe2e1e..1638b50 100644 > --- a/include/spi.h > +++ b/include/spi.h > @@ -37,11 +37,16 @@ > #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */ > #define SPI_3WIRE 0x10 /* SI/SO signals shared */ > #define SPI_LOOP 0x20 /* loopback mode */ > +#define SPI_SLAVE 0x40 /* slave mode */ > +#define SPI_PREAMBLE 0x80 /* Skip preamble bytes */ > > /* SPI transfer flags */ > #define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */ > #define SPI_XFER_END 0x02 /* Deassert CS after transfer */ > > +/* Header byte that marks the start of the message */ > +#define SPI_PREAMBLE_END_BYTE 0xec I think this 0xec is a value of rx_data what does it indicates and does this value specific to hw? -- Thanks, Jagan.
Hi, On Sun, Jun 2, 2013 at 10:24 AM, Jagan Teki <jagannadh.teki@gmail.com>wrote: > On Wed, May 29, 2013 at 11:40 AM, Rajeshwari Shinde > <rajeshwari.s@samsung.com> wrote: > > A SPI slave may take time to react to a request. For SPI flash devices > > this time is defined as one bit time, or a whole byte for 'fast read' > > mode. > > > > If the SPI slave is another CPU, then the time it takes to react may > > vary. It is convenient to allow the slave device to tag the start of > > the actual reply so that the host can determine when this 'preamble' > > finishes and the actual message starts. > > > > Add a preamble flag to the available SPI flags. If supported by the > > driver then it will ignore any received bytes before the preamble > > on each transaction. This ensures that reliable communication with > > the slave is possible. > > > > Signed-off-by: Simon Glass <sjg@chromium.org> > > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> > > --- > > Changes in V2: > > - None > > Changes in V3: > > - None. > > Changes in V4: > > - None. > > Changes in V5: > > - In commit message header changed SPI to spi. > > include/spi.h | 5 +++++ > > 1 files changed, 5 insertions(+), 0 deletions(-) > > > > diff --git a/include/spi.h b/include/spi.h > > index 3fe2e1e..1638b50 100644 > > --- a/include/spi.h > > +++ b/include/spi.h > > @@ -37,11 +37,16 @@ > > #define SPI_LSB_FIRST 0x08 /* per-word > bits-on-wire */ > > #define SPI_3WIRE 0x10 /* SI/SO signals > shared */ > > #define SPI_LOOP 0x20 /* loopback mode > */ > > +#define SPI_SLAVE 0x40 /* slave mode */ > > +#define SPI_PREAMBLE 0x80 /* Skip preamble > bytes */ > > > > /* SPI transfer flags */ > > #define SPI_XFER_BEGIN 0x01 /* Assert CS before > transfer */ > > #define SPI_XFER_END 0x02 /* Deassert CS after > transfer */ > > > > +/* Header byte that marks the start of the message */ > > +#define SPI_PREAMBLE_END_BYTE 0xec > > I think this 0xec is a value of rx_data what does it indicates and > does this value specific to hw? > We have a later change which generalises this using the device tree, but it is dependent on various other patches and adjusts the generic SPI interface. If we can get this one in then I'm sure Vadim will supply a new patch for consideration. > -- > Thanks, > Jagan. > Regards, Simon
On Sun, Jun 2, 2013 at 11:25 PM, Simon Glass <sjg@chromium.org> wrote: > Hi, > > On Sun, Jun 2, 2013 at 10:24 AM, Jagan Teki <jagannadh.teki@gmail.com> > wrote: >> >> On Wed, May 29, 2013 at 11:40 AM, Rajeshwari Shinde >> <rajeshwari.s@samsung.com> wrote: >> > A SPI slave may take time to react to a request. For SPI flash devices >> > this time is defined as one bit time, or a whole byte for 'fast read' >> > mode. >> > >> > If the SPI slave is another CPU, then the time it takes to react may >> > vary. It is convenient to allow the slave device to tag the start of >> > the actual reply so that the host can determine when this 'preamble' >> > finishes and the actual message starts. >> > >> > Add a preamble flag to the available SPI flags. If supported by the >> > driver then it will ignore any received bytes before the preamble >> > on each transaction. This ensures that reliable communication with >> > the slave is possible. >> > >> > Signed-off-by: Simon Glass <sjg@chromium.org> >> > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> >> > --- >> > Changes in V2: >> > - None >> > Changes in V3: >> > - None. >> > Changes in V4: >> > - None. >> > Changes in V5: >> > - In commit message header changed SPI to spi. >> > include/spi.h | 5 +++++ >> > 1 files changed, 5 insertions(+), 0 deletions(-) >> > >> > diff --git a/include/spi.h b/include/spi.h >> > index 3fe2e1e..1638b50 100644 >> > --- a/include/spi.h >> > +++ b/include/spi.h >> > @@ -37,11 +37,16 @@ >> > #define SPI_LSB_FIRST 0x08 /* per-word >> > bits-on-wire */ >> > #define SPI_3WIRE 0x10 /* SI/SO signals >> > shared */ >> > #define SPI_LOOP 0x20 /* loopback mode >> > */ >> > +#define SPI_SLAVE 0x40 /* slave mode */ >> > +#define SPI_PREAMBLE 0x80 /* Skip preamble >> > bytes */ >> > >> > /* SPI transfer flags */ >> > #define SPI_XFER_BEGIN 0x01 /* Assert CS before >> > transfer */ >> > #define SPI_XFER_END 0x02 /* Deassert CS after >> > transfer */ >> > >> > +/* Header byte that marks the start of the message */ >> > +#define SPI_PREAMBLE_END_BYTE 0xec >> >> I think this 0xec is a value of rx_data what does it indicates and >> does this value specific to hw? > > > We have a later change which generalises this using the device tree, but it > is dependent on various other patches and adjusts the generic SPI interface. > If we can get this one in then I'm sure Vadim will supply a new patch for > consideration. Means this value is specific to exynos is it? -- Thanks, Jagan.
Hi Jagan, On Sun, Jun 2, 2013 at 11:00 AM, Jagan Teki <jagannadh.teki@gmail.com>wrote: > On Sun, Jun 2, 2013 at 11:25 PM, Simon Glass <sjg@chromium.org> wrote: > > Hi, > > > > On Sun, Jun 2, 2013 at 10:24 AM, Jagan Teki <jagannadh.teki@gmail.com> > > wrote: > >> > >> On Wed, May 29, 2013 at 11:40 AM, Rajeshwari Shinde > >> <rajeshwari.s@samsung.com> wrote: > >> > A SPI slave may take time to react to a request. For SPI flash devices > >> > this time is defined as one bit time, or a whole byte for 'fast read' > >> > mode. > >> > > >> > If the SPI slave is another CPU, then the time it takes to react may > >> > vary. It is convenient to allow the slave device to tag the start of > >> > the actual reply so that the host can determine when this 'preamble' > >> > finishes and the actual message starts. > >> > > >> > Add a preamble flag to the available SPI flags. If supported by the > >> > driver then it will ignore any received bytes before the preamble > >> > on each transaction. This ensures that reliable communication with > >> > the slave is possible. > >> > > >> > Signed-off-by: Simon Glass <sjg@chromium.org> > >> > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> > >> > --- > >> > Changes in V2: > >> > - None > >> > Changes in V3: > >> > - None. > >> > Changes in V4: > >> > - None. > >> > Changes in V5: > >> > - In commit message header changed SPI to spi. > >> > include/spi.h | 5 +++++ > >> > 1 files changed, 5 insertions(+), 0 deletions(-) > >> > > >> > diff --git a/include/spi.h b/include/spi.h > >> > index 3fe2e1e..1638b50 100644 > >> > --- a/include/spi.h > >> > +++ b/include/spi.h > >> > @@ -37,11 +37,16 @@ > >> > #define SPI_LSB_FIRST 0x08 /* per-word > >> > bits-on-wire */ > >> > #define SPI_3WIRE 0x10 /* SI/SO > signals > >> > shared */ > >> > #define SPI_LOOP 0x20 /* loopback > mode > >> > */ > >> > +#define SPI_SLAVE 0x40 /* slave mode > */ > >> > +#define SPI_PREAMBLE 0x80 /* Skip > preamble > >> > bytes */ > >> > > >> > /* SPI transfer flags */ > >> > #define SPI_XFER_BEGIN 0x01 /* Assert CS before > >> > transfer */ > >> > #define SPI_XFER_END 0x02 /* Deassert CS after > >> > transfer */ > >> > > >> > +/* Header byte that marks the start of the message */ > >> > +#define SPI_PREAMBLE_END_BYTE 0xec > >> > >> I think this 0xec is a value of rx_data what does it indicates and > >> does this value specific to hw? > > > > > > We have a later change which generalises this using the device tree, but > it > > is dependent on various other patches and adjusts the generic SPI > interface. > > If we can get this one in then I'm sure Vadim will supply a new patch for > > consideration. > > Means this value is specific to exynos is it? > Yes, it is actually specific to snow, a particular board. We are working on generalising this using device tree, and moving this logic to the generic spi code, but these patches will come later, and sit on top of this one. These patches have now been outstanding on the list for a very long time, and have been thoroughly reviewed and tested. > > -- > Thanks, > Jagan. > Regards, Simon
On 29-05-2013 01:40, Rajeshwari Shinde wrote: > A SPI slave may take time to react to a request. For SPI flash devices > this time is defined as one bit time, or a whole byte for 'fast read' > mode. > > If the SPI slave is another CPU, then the time it takes to react may > vary. It is convenient to allow the slave device to tag the start of > the actual reply so that the host can determine when this 'preamble' > finishes and the actual message starts. > > Add a preamble flag to the available SPI flags. If supported by the > driver then it will ignore any received bytes before the preamble > on each transaction. This ensures that reliable communication with > the slave is possible. > > Signed-off-by: Simon Glass <sjg@chromium.org> > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> > > --- > Changes in V2: > - None > Changes in V3: > - None. > Changes in V4: > - None. > Changes in V5: > - In commit message header changed SPI to spi. > include/spi.h | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/include/spi.h b/include/spi.h > index 3fe2e1e..1638b50 100644 > --- a/include/spi.h > +++ b/include/spi.h > @@ -37,11 +37,16 @@ > #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */ > #define SPI_3WIRE 0x10 /* SI/SO signals shared */ > #define SPI_LOOP 0x20 /* loopback mode */ > +#define SPI_SLAVE 0x40 /* slave mode */ > +#define SPI_PREAMBLE 0x80 /* Skip preamble bytes */ > > /* SPI transfer flags */ > #define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */ > #define SPI_XFER_END 0x02 /* Deassert CS after transfer */ > > +/* Header byte that marks the start of the message */ > +#define SPI_PREAMBLE_END_BYTE 0xec > + > /*----------------------------------------------------------------------- > * Representation of a SPI slave, i.e. what we're communicating with. > * Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com> -- Thanks, Jagan.
On 29-05-2013 01:40, Rajeshwari Shinde wrote: > A SPI slave may take time to react to a request. For SPI flash devices > this time is defined as one bit time, or a whole byte for 'fast read' > mode. > > If the SPI slave is another CPU, then the time it takes to react may > vary. It is convenient to allow the slave device to tag the start of > the actual reply so that the host can determine when this 'preamble' > finishes and the actual message starts. > > Add a preamble flag to the available SPI flags. If supported by the > driver then it will ignore any received bytes before the preamble > on each transaction. This ensures that reliable communication with > the slave is possible. > > Signed-off-by: Simon Glass <sjg@chromium.org> > Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> > Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com> > > --- > Changes in V2: > - None > Changes in V3: > - None. > Changes in V4: > - None. > Changes in V5: > - In commit message header changed SPI to spi. > include/spi.h | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/include/spi.h b/include/spi.h > index 3fe2e1e..1638b50 100644 > --- a/include/spi.h > +++ b/include/spi.h > @@ -37,11 +37,16 @@ > #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */ > #define SPI_3WIRE 0x10 /* SI/SO signals shared */ > #define SPI_LOOP 0x20 /* loopback mode */ > +#define SPI_SLAVE 0x40 /* slave mode */ > +#define SPI_PREAMBLE 0x80 /* Skip preamble bytes */ > > /* SPI transfer flags */ > #define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */ > #define SPI_XFER_END 0x02 /* Deassert CS after transfer */ > > +/* Header byte that marks the start of the message */ > +#define SPI_PREAMBLE_END_BYTE 0xec > + > /*----------------------------------------------------------------------- > * Representation of a SPI slave, i.e. what we're communicating with. > * Applied to u-boot-spi/master -- Thanks, Jagan.
diff --git a/include/spi.h b/include/spi.h index 3fe2e1e..1638b50 100644 --- a/include/spi.h +++ b/include/spi.h @@ -37,11 +37,16 @@ #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */ #define SPI_3WIRE 0x10 /* SI/SO signals shared */ #define SPI_LOOP 0x20 /* loopback mode */ +#define SPI_SLAVE 0x40 /* slave mode */ +#define SPI_PREAMBLE 0x80 /* Skip preamble bytes */ /* SPI transfer flags */ #define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */ #define SPI_XFER_END 0x02 /* Deassert CS after transfer */ +/* Header byte that marks the start of the message */ +#define SPI_PREAMBLE_END_BYTE 0xec + /*----------------------------------------------------------------------- * Representation of a SPI slave, i.e. what we're communicating with. *