linux-kernel - Re: [PATCH v3] soundwire: SDCA: add helper macro to access controls

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Date:   Fri, 30 Oct 2020 10:36:51 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, vkoul@...nel.org,
        vinod.koul@...aro.org, linux-kernel@...r.kernel.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        rander.wang@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        hui.wang@...onical.com, pierre-louis.bossart@...ux.intel.com,
        sanyog.r.kale@...el.com, mengdong.lin@...el.com,
        bard.liao@...el.com
Subject: Re: [PATCH v3] soundwire: SDCA: add helper macro to access controls

On Fri, Oct 30, 2020 at 04:49:55AM +0800, Bard Liao wrote:
> From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> 
> The upcoming SDCA (SoundWire Device Class Audio) specification defines
> a hierarchical encoding to interface with Class-defined capabilities.
> 
> The specification is not yet accessible to the general public but this
> information is released with explicit permission from the MIPI Board
> to avoid delays with SDCA support on Linux platforms.
> 
> A block of 64 MBytes of register addresses are allocated to SDCA
> controls, starting at address 0x40000000. The 26 LSBs which identify
> individual controls are set based on the following variables:
> 
> - Function Number. An SCDA device can be split in up to 8 independent
>   Functions. Each of these Functions is described in the SDCA
>   specification, e.g. Smart Amplifier, Smart Microphone, Simple
>   Microphone, Jack codec, HID, etc.
> 
> - Entity Number.  Within each Function,  an Entity is  an identifiable
>   block.  Up   to  127  Entities   are  connected  in   a  pre-defined
>   graph  (similar to  USB), with  Entity0 reserved  for Function-level
>   configurations.  In  contrast  to  USB, the  SDCA  spec  pre-defines
>   Function Types, topologies, and allowed  options, i.e. the degree of
>   freedom  is not  unlimited to  limit  the possibility  of errors  in
>   descriptors leading to software quirks.
> 
> - Control Selector. Within each Entity, the SDCA specification defines
>   48 controls such as Mute, Gain, AGC, etc, and 16 implementation
>   defined ones. Some Control Selectors might be used for low-level
>   platform setup, and other exposed to applications and users. Note
>   that the same Control Selector capability, e.g. Latency control,
>   might be located at different offsets in different entities, the
>   Control Selector mapping is Entity-specific.
> 
> - Control Number. Some Control Selectors allow channel-specific values
>   to be set, with up to 64 channels allowed. This is mostly used for
>   volume control.
> 
> - Current/Next values. Some Control Selectors are
>   'Dual-Ranked'. Software may either update the Current value directly
>   for immediate effect. Alternatively, software may write into the
>   'Next' values and update the SoundWire 1.2 'Commit Groups' register
>   to copy 'Next' values into 'Current' ones in a synchronized
>   manner. This is different from bank switching which is typically
>   used to change the bus configuration only.
> 
> - MBQ. the Multi-Byte Quantity bit is used to provide atomic updates
>   when accessing more that one byte, for example a 16-bit volume
>   control would be updated consistently, the intermediate values
>   mixing old MSB with new LSB are not applied.
> 
> These 6 parameters are used to build a 32-bit address to access the
> desired Controls. Because of address range, paging is required, but
> the most often used parameter values are placed in the lower 16 bits
> of the address. This helps to keep the paging registers constant while
> updating Controls for a specific Device/Function.
> 
> Reviewed-by: Rander Wang <rander.wang@...ux.intel.com>
> Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>
> Reviewed-by: Kai Vehmanen <kai.vehmanen@...ux.intel.com>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
> ---
> Changelog:
> 
> v2:
>  - add SDW_SDCA_MBQ_CTL
> 
> v3:
>  - add SDW_SDCA_NEXT_CTL
> 
> ---
>  include/linux/soundwire/sdw_registers.h | 32 +++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/include/linux/soundwire/sdw_registers.h b/include/linux/soundwire/sdw_registers.h
> index f420e8059779..e14dff9a9c7f 100644
> --- a/include/linux/soundwire/sdw_registers.h
> +++ b/include/linux/soundwire/sdw_registers.h
> @@ -298,4 +298,36 @@
>  #define SDW_CASC_PORT_MASK_INTSTAT3		1
>  #define SDW_CASC_PORT_REG_OFFSET_INTSTAT3	2
>  
> +/*
> + * v1.2 device - SDCA address mapping
> + *
> + * Spec definition
> + *	Bits		Contents
> + *	31		0 (required by addressing range)
> + *	30:26		0b10000 (Control Prefix)
> + *	25		0 (Reserved)
> + *	24:22		Function Number [2:0]
> + *	21		Entity[6]
> + *	20:19		Control Selector[5:4]
> + *	18		0 (Reserved)
> + *	17:15		Control Number[5:3]
> + *	14		Next
> + *	13		MBQ
> + *	12:7		Entity[5:0]
> + *	6:3		Control Selector[3:0]
> + *	2:0		Control Number[2:0]
> + */
> +
> +#define SDW_SDCA_CTL(fun, ent, ctl, ch)		(BIT(30) |			\
> +						 (((fun) & 0x7) << 22) |	\
> +						 (((ent) & 0x40) << 15) |	\
> +						 (((ent) & 0x3f) << 7) |	\
> +						 (((ctl) & 0x30) << 15) |	\
> +						 (((ctl) & 0x0f) << 3) |	\
> +						 (((ch) & 0x38) << 12) |	\
> +						 ((ch) & 0x07))
> +
> +#define SDW_SDCA_MBQ_CTL(reg)			((reg) | BIT(13))
> +#define SDW_SDCA_NEXT_CTL(reg)			((reg) | BIT(14))
> +
>  #endif /* __SDW_REGISTERS_H */


No users of these macros?