linux-kernel - RE: [PATCH v4 05/27] bus: mhi: Use bitfield operations for handling DWORDs of ring elements

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Message-ID: <90b1d3954b8c4157a4045db82b562271@AcuMS.aculab.com>
Date:   Mon, 28 Feb 2022 14:00:07 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Manivannan Sadhasivam' <manivannan.sadhasivam@...aro.org>,
        "mhi@...ts.linux.dev" <mhi@...ts.linux.dev>
CC:     "quic_hemantk@...cinc.com" <quic_hemantk@...cinc.com>,
        "quic_bbhatt@...cinc.com" <quic_bbhatt@...cinc.com>,
        "quic_jhugo@...cinc.com" <quic_jhugo@...cinc.com>,
        "vinod.koul@...aro.org" <vinod.koul@...aro.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
        "quic_vbadigan@...cinc.com" <quic_vbadigan@...cinc.com>,
        "quic_cang@...cinc.com" <quic_cang@...cinc.com>,
        "quic_skananth@...cinc.com" <quic_skananth@...cinc.com>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "elder@...aro.org" <elder@...aro.org>
Subject: RE: [PATCH v4 05/27] bus: mhi: Use bitfield operations for handling
 DWORDs of ring elements

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.
Try reading it!

	David

> 
> Suggested-by: Alex Elder <elder@...aro.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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

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