linux-kernel - Re: [PATCH v5 09/13] soc: mediatek: cmdq: add write

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Message-ID: <1590403125.11988.5.camel@mtkswgap22>
Date:   Mon, 25 May 2020 18:38:45 +0800
From:   Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <wsd_upstream@...iatek.com>, <dri-devel@...ts.freedesktop.org>,
        Bibby Hsieh <bibby.hsieh@...iatek.com>,
        CK Hu <ck.hu@...iatek.com>,
        Houlong Wei <houlong.wei@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        HS Liao <hs.liao@...iatek.com>
Subject: Re: [PATCH v5 09/13] soc: mediatek: cmdq: add write_s value function


On Mon, 2020-05-25 at 10:39 +0200, Matthias Brugger wrote:
> 
> On 25/05/2020 04:27, Dennis-YC Hsieh wrote:
> > 
> > On Sun, 2020-05-24 at 20:13 +0200, Matthias Brugger wrote:
> >>
> >> On 24/05/2020 19:31, Dennis-YC Hsieh wrote:
> >>> Hi Matthias,
> >>>
> >>> Thanks for your comment.
> >>>
> >>> On Sat, 2020-05-16 at 20:20 +0200, Matthias Brugger wrote:
> >>>>
> >>>> On 08/03/2020 11:52, Dennis YC Hsieh wrote:
> >>>>> add write_s function in cmdq helper functions which
> >>>>> writes a constant value to address with large dma
> >>>>> access support.
> >>>>>
> >>>>> Signed-off-by: Dennis YC Hsieh <dennis-yc.hsieh@...iatek.com>
> >>>>> Reviewed-by: CK Hu <ck.hu@...iatek.com>
> >>>>> ---
> >>>>>  drivers/soc/mediatek/mtk-cmdq-helper.c | 26 ++++++++++++++++++++++++++
> >>>>>  include/linux/soc/mediatek/mtk-cmdq.h  | 14 ++++++++++++++
> >>>>>  2 files changed, 40 insertions(+)
> >>>>>
> >>>>> diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>>>> index 03c129230cd7..a9ebbabb7439 100644
> >>>>> --- a/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>>>> +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
> >>>>> @@ -269,6 +269,32 @@ int cmdq_pkt_write_s(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>>>>  }
> >>>>>  EXPORT_SYMBOL(cmdq_pkt_write_s);
> >>>>>  
> >>>>> +int cmdq_pkt_write_s_value(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>>>> +			   u16 addr_low, u32 value, u32 mask)
> >>>>> +{
> >>>>> +	struct cmdq_instruction inst = { {0} };
> >>>>> +	int err;
> >>>>> +
> >>>>> +	if (mask != U32_MAX) {
> >>>>> +		inst.op = CMDQ_CODE_MASK;
> >>>>> +		inst.mask = ~mask;
> >>>>> +		err = cmdq_pkt_append_command(pkt, inst);
> >>>>> +		if (err < 0)
> >>>>> +			return err;
> >>>>> +
> >>>>> +		inst.op = CMDQ_CODE_WRITE_S_MASK;
> >>>>> +	} else {
> >>>>> +		inst.op = CMDQ_CODE_WRITE_S;
> >>>>> +	}
> >>>>> +
> >>>>> +	inst.sop = high_addr_reg_idx;
> >>>>
> >>>> Writing u16 value in a 5 bit wide variable?
> >>>
> >>> We need only 5 bits in this case. I'll change high_addr_reg_idx
> >>> parameter to u8.
> >>>
> >>
> >> Ok, please make sure to mask the value, so that it's explicit in the code that
> >> we only use the lowest 5 bits of high_addr_reg_idx.
> > 
> > Is it necessary to mask the value?
> > Since sop already defined as "u8 sop:5;", I thought it is explicit that
> > only use 5 bits and compiler should do the rest jobs.
> 
> Yes but it makes the code more explicit if we have a
> inst.sop = high_addr_reg_idx & 0x1f;
> 
> What do you think?

The value assign to sop will restrict by hardware spec. Clients call
this function will define constant value and use it as parameter. So I
think we don't worry about client call this api with wrong value.


Regards,
Dennis

> 
> Regards,
> Matthias
> 
> > 
> > 
> > Regards,
> > Dennis
> > 
> >>
> >> Regards,
> >> Matthias
> >>
> >>>>
> >>>>> +	inst.offset = addr_low;
> >>>>> +	inst.value = value;
> >>>>> +
> >>>>> +	return cmdq_pkt_append_command(pkt, inst);
> >>>>> +}
> >>>>> +EXPORT_SYMBOL(cmdq_pkt_write_s_value);
> >>>>> +
> >>>>>  int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event)
> >>>>>  {
> >>>>>  	struct cmdq_instruction inst = { {0} };
> >>>>> diff --git a/include/linux/soc/mediatek/mtk-cmdq.h b/include/linux/soc/mediatek/mtk-cmdq.h
> >>>>> index 01b4184af310..fec292aac83c 100644
> >>>>> --- a/include/linux/soc/mediatek/mtk-cmdq.h
> >>>>> +++ b/include/linux/soc/mediatek/mtk-cmdq.h
> >>>>> @@ -135,6 +135,20 @@ int cmdq_pkt_read_s(struct cmdq_pkt *pkt, u16 high_addr_reg_idx, u16 addr_low,
> >>>>>  int cmdq_pkt_write_s(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>>>>  		     u16 addr_low, u16 src_reg_idx, u32 mask);
> >>>>>  
> >>>>> +/**
> >>>>> + * cmdq_pkt_write_s_value() - append write_s command with mask to the CMDQ
> >>>>> + *			      packet which write value to a physical address
> >>>>> + * @pkt:	the CMDQ packet
> >>>>> + * @high_addr_reg_idx:	internal regisger ID which contains high address of pa
> >>>>
> >>>> register
> >>>
> >>> will fix
> >>>
> >>>
> >>> Regards,
> >>> Dennis
> >>>
> >>>>
> >>>>> + * @addr_low:	low address of pa
> >>>>> + * @value:	the specified target value
> >>>>> + * @mask:	the specified target mask
> >>>>> + *
> >>>>> + * Return: 0 for success; else the error code is returned
> >>>>> + */
> >>>>> +int cmdq_pkt_write_s_value(struct cmdq_pkt *pkt, u16 high_addr_reg_idx,
> >>>>> +			   u16 addr_low, u32 value, u32 mask);
> >>>>> +
> >>>>>  /**
> >>>>>   * cmdq_pkt_wfe() - append wait for event command to the CMDQ packet
> >>>>>   * @pkt:	the CMDQ packet
> >>>>>
> >>>
> >