Re: [PATCH v4 05/27] bus: mhi: Use bitfield operations for handling DWORDs of ring elements

['Manivannan Sadhasivam' <manivannan.sadhasivam@linaro.org>]

On Mon, Feb 28, 2022 at 02:00:07PM +0000, David Laight wrote:
> From: Manivannan Sadhasivam
> > Sent: 28 February 2022 12:43
> > 
> > Instead of using the hardcoded bits in DWORD definitions, let's use the
> > bitfield operations to make it more clear how the DWORDs are structured.
> 
> That all makes it as clear as mud.

It depends on how you see it ;)

For instance,

#define MHI_TRE_GET_CMD_TYPE(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 16) & 0xFF)

vs

#define MHI_TRE_GET_CMD_TYPE(tre) (FIELD_GET(GENMASK(23, 16), (MHI_TRE_GET_DWORD(tre, 1))))

The later one makes it more obvious that the "type" field resides between bit 23
and 16. Plus it avoids the extra masking.

> Try reading it!
> 

Well I did before sending the patch.

Thanks,
Mani

> 	David
> 
> > 
> > Suggested-by: Alex Elder <elder@linaro.org>
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > ---
> >  drivers/bus/mhi/host/internal.h | 58 +++++++++++++++++++--------------
> >  1 file changed, 33 insertions(+), 25 deletions(-)
> > 
> > diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
> > index 156bf65b6810..1d1790e83a93 100644
> > --- a/drivers/bus/mhi/host/internal.h
> > +++ b/drivers/bus/mhi/host/internal.h
> > @@ -7,6 +7,7 @@
> >  #ifndef _MHI_INT_H
> >  #define _MHI_INT_H
> > 
> > +#include <linux/bitfield.h>
> >  #include <linux/mhi.h>
> > 
> >  extern struct bus_type mhi_bus_type;
> > @@ -205,58 +206,65 @@ enum mhi_cmd_type {
> >  /* No operation command */
> >  #define MHI_TRE_CMD_NOOP_PTR (0)
> >  #define MHI_TRE_CMD_NOOP_DWORD0 (0)
> > -#define MHI_TRE_CMD_NOOP_DWORD1 (cpu_to_le32(MHI_CMD_NOP << 16))
> > +#define MHI_TRE_CMD_NOOP_DWORD1 (cpu_to_le32(FIELD_PREP(GENMASK(23, 16), MHI_CMD_NOP)))
> > 
> >  /* Channel reset command */
> >  #define MHI_TRE_CMD_RESET_PTR (0)
> >  #define MHI_TRE_CMD_RESET_DWORD0 (0)
> > -#define MHI_TRE_CMD_RESET_DWORD1(chid) (cpu_to_le32((chid << 24) | \
> > -					(MHI_CMD_RESET_CHAN << 16)))
> > +#define MHI_TRE_CMD_RESET_DWORD1(chid) (cpu_to_le32(FIELD_PREP(GENMASK(31, 24), chid)) | \
> > +					FIELD_PREP(GENMASK(23, 16), MHI_CMD_RESET_CHAN))
> > 
> >  /* Channel stop command */
> >  #define MHI_TRE_CMD_STOP_PTR (0)
> >  #define MHI_TRE_CMD_STOP_DWORD0 (0)
> > -#define MHI_TRE_CMD_STOP_DWORD1(chid) (cpu_to_le32((chid << 24) | \
> > -				       (MHI_CMD_STOP_CHAN << 16)))
> > +#define MHI_TRE_CMD_STOP_DWORD1(chid) (cpu_to_le32(FIELD_PREP(GENMASK(31, 24), chid)) | \
> > +					FIELD_PREP(GENMASK(23, 16), MHI_CMD_STOP_CHAN))
> > 
> >  /* Channel start command */
> >  #define MHI_TRE_CMD_START_PTR (0)
> >  #define MHI_TRE_CMD_START_DWORD0 (0)
> > -#define MHI_TRE_CMD_START_DWORD1(chid) (cpu_to_le32((chid << 24) | \
> > -					(MHI_CMD_START_CHAN << 16)))
> > +#define MHI_TRE_CMD_START_DWORD1(chid) (cpu_to_le32(FIELD_PREP(GENMASK(31, 24), chid)) | \
> > +					FIELD_PREP(GENMASK(23, 16), MHI_CMD_START_CHAN))
> > 
> >  #define MHI_TRE_GET_DWORD(tre, word) (le32_to_cpu((tre)->dword[(word)]))
> > -#define MHI_TRE_GET_CMD_CHID(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 24) & 0xFF)
> > -#define MHI_TRE_GET_CMD_TYPE(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 16) & 0xFF)
> > +#define MHI_TRE_GET_CMD_CHID(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 1))))
> > +#define MHI_TRE_GET_CMD_TYPE(tre) (FIELD_GET(GENMASK(23, 16), (MHI_TRE_GET_DWORD(tre, 1))))
> > 
> >  /* Event descriptor macros */
> >  #define MHI_TRE_EV_PTR(ptr) (cpu_to_le64(ptr))
> > -#define MHI_TRE_EV_DWORD0(code, len) (cpu_to_le32((code << 24) | len))
> > -#define MHI_TRE_EV_DWORD1(chid, type) (cpu_to_le32((chid << 24) | (type << 16)))
> > +#define MHI_TRE_EV_DWORD0(code, len) (cpu_to_le32(FIELD_PREP(GENMASK(31, 24), code) | \
> > +						FIELD_PREP(GENMASK(15, 0), len)))
> > +#define MHI_TRE_EV_DWORD1(chid, type) (cpu_to_le32(FIELD_PREP(GENMASK(31, 24), chid) | \
> > +						FIELD_PREP(GENMASK(23, 16), type)))
> >  #define MHI_TRE_GET_EV_PTR(tre) (le64_to_cpu((tre)->ptr))
> > -#define MHI_TRE_GET_EV_CODE(tre) ((MHI_TRE_GET_DWORD(tre, 0) >> 24) & 0xFF)
> > -#define MHI_TRE_GET_EV_LEN(tre) (MHI_TRE_GET_DWORD(tre, 0) & 0xFFFF)
> > -#define MHI_TRE_GET_EV_CHID(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 24) & 0xFF)
> > -#define MHI_TRE_GET_EV_TYPE(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 16) & 0xFF)
> > -#define MHI_TRE_GET_EV_STATE(tre) ((MHI_TRE_GET_DWORD(tre, 0) >> 24) & 0xFF)
> > -#define MHI_TRE_GET_EV_EXECENV(tre) ((MHI_TRE_GET_DWORD(tre, 0) >> 24) & 0xFF)
> > +#define MHI_TRE_GET_EV_CODE(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 0))))
> > +#define MHI_TRE_GET_EV_LEN(tre) (FIELD_GET(GENMASK(15, 0), (MHI_TRE_GET_DWORD(tre, 0))))
> > +#define MHI_TRE_GET_EV_CHID(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 1))))
> > +#define MHI_TRE_GET_EV_TYPE(tre) (FIELD_GET(GENMASK(23, 16), (MHI_TRE_GET_DWORD(tre, 1))))
> > +#define MHI_TRE_GET_EV_STATE(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 0))))
> > +#define MHI_TRE_GET_EV_EXECENV(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 0))))
> >  #define MHI_TRE_GET_EV_SEQ(tre) MHI_TRE_GET_DWORD(tre, 0)
> >  #define MHI_TRE_GET_EV_TIME(tre) (MHI_TRE_GET_EV_PTR(tre))
> >  #define MHI_TRE_GET_EV_COOKIE(tre) lower_32_bits(MHI_TRE_GET_EV_PTR(tre))
> > -#define MHI_TRE_GET_EV_VEID(tre) ((MHI_TRE_GET_DWORD(tre, 0) >> 16) & 0xFF)
> > -#define MHI_TRE_GET_EV_LINKSPEED(tre) ((MHI_TRE_GET_DWORD(tre, 1) >> 24) & 0xFF)
> > -#define MHI_TRE_GET_EV_LINKWIDTH(tre) (MHI_TRE_GET_DWORD(tre, 0) & 0xFF)
> > +#define MHI_TRE_GET_EV_VEID(tre) (FIELD_GET(GENMASK(23, 16), (MHI_TRE_GET_DWORD(tre, 0))))
> > +#define MHI_TRE_GET_EV_LINKSPEED(tre) (FIELD_GET(GENMASK(31, 24), (MHI_TRE_GET_DWORD(tre, 1))))
> > +#define MHI_TRE_GET_EV_LINKWIDTH(tre) (FIELD_GET(GENMASK(7, 0), (MHI_TRE_GET_DWORD(tre, 0))))
> > 
> >  /* Transfer descriptor macros */
> >  #define MHI_TRE_DATA_PTR(ptr) (cpu_to_le64(ptr))
> > -#define MHI_TRE_DATA_DWORD0(len) (cpu_to_le32(len & MHI_MAX_MTU))
> > -#define MHI_TRE_DATA_DWORD1(bei, ieot, ieob, chain) (cpu_to_le32((2 << 16) | (bei << 10) \
> > -	| (ieot << 9) | (ieob << 8) | chain))
> > +#define MHI_TRE_DATA_DWORD0(len) (cpu_to_le32(FIELD_PREP(GENMASK(15, 0), len)))
> > +#define MHI_TRE_TYPE_TRANSFER 2
> > +#define MHI_TRE_DATA_DWORD1(bei, ieot, ieob, chain) (cpu_to_le32(FIELD_PREP(GENMASK(23, 16), \
> > +							MHI_TRE_TYPE_TRANSFER) | \
> > +							FIELD_PREP(BIT(10), bei) | \
> > +							FIELD_PREP(BIT(9), ieot) | \
> > +							FIELD_PREP(BIT(8), ieob) | \
> > +							FIELD_PREP(BIT(0), chain)))
> > 
> >  /* RSC transfer descriptor macros */
> > -#define MHI_RSCTRE_DATA_PTR(ptr, len) (cpu_to_le64(((u64)len << 48) | ptr))
> > +#define MHI_RSCTRE_DATA_PTR(ptr, len) (cpu_to_le64(FIELD_PREP(GENMASK(64, 48), len) | ptr))
> >  #define MHI_RSCTRE_DATA_DWORD0(cookie) (cpu_to_le32(cookie))
> > -#define MHI_RSCTRE_DATA_DWORD1 (cpu_to_le32(MHI_PKT_TYPE_COALESCING << 16))
> > +#define MHI_RSCTRE_DATA_DWORD1 (cpu_to_le32(FIELD_PREP(GENMASK(23, 16), MHI_PKT_TYPE_COALESCING)
> > 
> >  enum mhi_pkt_type {
> >  	MHI_PKT_TYPE_INVALID = 0x0,
> > --
> > 2.25.1
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>