Re: [PATCH v1 03/11] soc: mediatek: cmdq: add write_s function

[Dennis-YC Hsieh <dennis-yc.hsieh@mediatek.com>]

Hi Matthias,

On Mon, 2020-06-22 at 17:54 +0200, Matthias Brugger wrote:
> 
> On 22/06/2020 17:36, Dennis-YC Hsieh wrote:
> > Hi Matthias,
> > 
> > thanks for your comment.
> > 
> > On Mon, 2020-06-22 at 13:07 +0200, Matthias Brugger wrote:
> >>
> >> On 21/06/2020 16:18, Dennis YC Hsieh wrote:
> >>> add write_s function in cmdq helper functions which
> >>> writes value contains in internal register to address
> >>> with large dma access support.
> >>>
> >>> Signed-off-by: Dennis YC Hsieh <dennis-yc.hsieh@mediatek.com>
> >>> ---
> >>>  drivers/soc/mediatek/mtk-cmdq-helper.c   |   19 +++++++++++++++++++
> >>>  include/linux/mailbox/mtk-cmdq-mailbox.h |    1 +
> >>>  include/linux/soc/mediatek/mtk-cmdq.h    |   19 +++++++++++++++++++
> >>>  3 files changed, 39 insertions(+)
> >>>
> >>> diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>> index bf32e3b2ca6c..817a5a97dbe5 100644
> >>> --- a/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>> +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>> @@ -18,6 +18,10 @@ struct cmdq_instruction {
> >>>  	union {
> >>>  		u32 value;
> >>>  		u32 mask;
> >>> +		struct {
> >>> +			u16 arg_c;
> >>> +			u16 src_reg;
> >>> +		};
> >>>  	};
> >>>  	union {
> >>>  		u16 offset;
> >>> @@ -222,6 +226,21 @@ int cmdq_pkt_write_mask(struct cmdq_pkt *pkt, u8 subsys,
> >>>  }
> >>>  EXPORT_SYMBOL(cmdq_pkt_write_mask);
> >>>  
> >>> +int cmdq_pkt_write_s(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>> +		     u16 addr_low, u16 src_reg_idx)
> >>> +{
> >>
> >> Do I understand correctly that we use CMDQ_ADDR_HIGH(addr) and
> >> CMDQ_ADDR_LOW(addr) to calculate in the client high_addr_reg_idx and addr_low
> >> respectively?
> >>
> >> In that case I think a better interface would be to pass the address and do the
> >> high/low calculation in the cmdq_pkt_write_s
> > 
> > Not exactly. The high_addr_reg_idx parameter is index of internal
> > register (which store address bit[47:16]), not result of
> > CMDQ_ADDR_HIGH(addr). 
> > 
> > The CMDQ_ADDR_HIGH macro use in patch 02/11 cmdq_pkt_assign() api. This
> > api helps assign address bit[47:16] into one of internal register by
> > index. And same index could be use in cmdq_pkt_write_s(). The gce
> > combine bit[47:16] in internal register and bit[15:0] in addr_low
> > parameter to final address. So it is better to keep interface in this
> > way.
> > 
> 
> Got it, but then why don't we call cmdq_pkt_assign() in cmdq_pkt_write_s()? This
> way we would get a clean API for what we want to do.
> Do we expect other users of cmdq_pkt_assign()? Otherwise we could keep it
> private the this file and don't export it.

Considering this case: write 2 register 0xaabb00c0 0xaabb00d0.

If we call assign inside write_s api it will be:
assign aabb to internal reg 0
write reg 0 + 0x00c0
assign aabb to internal reg 0
write reg 0 + 0x00d0


But if we let client decide timing to call assign, it will be like:
assign aabb to internal reg 0
write reg 0 + 0x00c0
write reg 0 + 0x00d0


The first way uses 4 command and second one uses only 3 command.
Thus it is better to let client call assign explicitly.

> 
> By the way, why do you postfix the _s, I understand that it reflects the large
> DMA access but I wonder why you choose '_s'.
> 

The name of this command is "write_s" which is hardware spec.
I'm just following it since it is a common language between gce sw/hw
designers.


Regards,
Dennis

> Regards,
> Matthias
> 
> > 
> > Regards,
> > Dennis
> > 
> >>
> >> Regards,
> >> Matthias
> >>
> >>> +	struct cmdq_instruction inst = {};
> >>> +
> >>> +	inst.op = CMDQ_CODE_WRITE_S;
> >>> +	inst.src_t = CMDQ_REG_TYPE;
> >>> +	inst.sop = high_addr_reg_idx;
> >>> +	inst.offset = addr_low;
> >>> +	inst.src_reg = src_reg_idx;
> >>> +
> >>> +	return cmdq_pkt_append_command(pkt, inst);
> >>> +}
> >>> +EXPORT_SYMBOL(cmdq_pkt_write_s);
> >>> +
> >>>  int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event)
> >>>  {
> >>>  	struct cmdq_instruction inst = { {0} };
> >>> diff --git a/include/linux/mailbox/mtk-cmdq-mailbox.h b/include/linux/mailbox/mtk-cmdq-mailbox.h
> >>> index 121c3bb6d3de..ee67dd3b86f5 100644
> >>> --- a/include/linux/mailbox/mtk-cmdq-mailbox.h
> >>> +++ b/include/linux/mailbox/mtk-cmdq-mailbox.h
> >>> @@ -59,6 +59,7 @@ enum cmdq_code {
> >>>  	CMDQ_CODE_JUMP = 0x10,
> >>>  	CMDQ_CODE_WFE = 0x20,
> >>>  	CMDQ_CODE_EOC = 0x40,
> >>> +	CMDQ_CODE_WRITE_S = 0x90,
> >>>  	CMDQ_CODE_LOGIC = 0xa0,
> >>>  };
> >>>  
> >>> diff --git a/include/linux/soc/mediatek/mtk-cmdq.h b/include/linux/soc/mediatek/mtk-cmdq.h
> >>> index 83340211e1d3..e1c5a7549b4f 100644
> >>> --- a/include/linux/soc/mediatek/mtk-cmdq.h
> >>> +++ b/include/linux/soc/mediatek/mtk-cmdq.h
> >>> @@ -12,6 +12,8 @@
> >>>  #include <linux/timer.h>
> >>>  
> >>>  #define CMDQ_NO_TIMEOUT		0xffffffffu
> >>> +#define CMDQ_ADDR_HIGH(addr)	((u32)(((addr) >> 16) & GENMASK(31, 0)))
> >>> +#define CMDQ_ADDR_LOW(addr)	((u16)(addr) | BIT(1))
> >>>  
> >>>  struct cmdq_pkt;
> >>>  
> >>> @@ -103,6 +105,23 @@ int cmdq_pkt_write_mask(struct cmdq_pkt *pkt, u8 subsys,
> >>>  			u16 offset, u32 value, u32 mask);
> >>>  
> >>>  /**
> >>> + * cmdq_pkt_write_s() - append write_s command to the CMDQ packet
> >>> + * @pkt:	the CMDQ packet
> >>> + * @high_addr_reg_idx:	internal register ID which contains high address of pa
> >>> + * @addr_low:	low address of pa
> >>> + * @src_reg_idx:	the CMDQ internal register ID which cache source value
> >>> + *
> >>> + * Return: 0 for success; else the error code is returned
> >>> + *
> >>> + * Support write value to physical address without subsys. Use CMDQ_ADDR_HIGH()
> >>> + * to get high address and call cmdq_pkt_assign() to assign value into internal
> >>> + * reg. Also use CMDQ_ADDR_LOW() to get low address for addr_low parameter when
> >>> + * call to this function.
> >>> + */
> >>> +int cmdq_pkt_write_s(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>> +		     u16 addr_low, u16 src_reg_idx);
> >>> +
> >>> +/**
> >>>   * cmdq_pkt_wfe() - append wait for event command to the CMDQ packet
> >>>   * @pkt:	the CMDQ packet
> >>>   * @event:	the desired event type to "wait and CLEAR"
> >>>
> >