Date:   Fri, 14 Feb 2020 14:33:40 +0800
From:   Weiyi Lu <weiyi.lu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     Rob Herring <robh@...nel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        <srv_heupstream@...iatek.com>,
        James Liao <jamesjj.liao@...iatek.com>,
        <linux-kernel@...r.kernel.org>, Fan Chen <fan.chen@...iatek.com>,
        <linux-mediatek@...ts.infradead.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v11 06/10] soc: mediatek: Add subsys clock control for
 bus protection

On Thu, 2020-02-13 at 13:56 +0100, Matthias Brugger wrote:
> 
> On 13/02/2020 03:46, Weiyi Lu wrote:
> > On Wed, 2020-02-12 at 12:02 +0100, Matthias Brugger wrote:
> >>
> >> On 12/02/2020 03:55, Weiyi Lu wrote:
> >>> On Tue, 2020-02-11 at 18:54 +0100, Matthias Brugger wrote:
> >>>>
> >>>> On 20/12/2019 04:46, Weiyi Lu wrote:
> >>>>> Add subsys CG control flow before/after the bus protect control
> >>>>> due to bus protection need SMI bus relative CGs enabled to feedback
> >>>>> its ack.
> >>>>>
> >>>>
> >>>> Sorry, I don't understand the commit message. Can you please rephrase and
> >>>> explain better what this change is for.
> >>>>
> >>>
> >>> OK! I'll reword it.
> >>>
> >>>>> Signed-off-by: Weiyi Lu <weiyi.lu@...iatek.com>
> >>>>> Reviewed-by: Nicolas Boichat <drinkcat@...omium.org>
> >>>>> ---
> >>>>>  drivers/soc/mediatek/mtk-scpsys.c | 72 +++++++++++++++++++++++++++++++++++++--
> >>>>>  1 file changed, 70 insertions(+), 2 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> >>>>> index 763ca58..32be4b3 100644
> >>>>> --- a/drivers/soc/mediatek/mtk-scpsys.c
> >>>>> +++ b/drivers/soc/mediatek/mtk-scpsys.c
> >>>>> @@ -79,6 +79,7 @@
> >>>>>  #define PWR_STATUS_WB			BIT(27)	/* MT7622 */
> >>>>>  
> >>>>>  #define MAX_CLKS	3
> >>>>> +#define MAX_SUBSYS_CLKS 10
> >>>>>  
> >>>>>  /**
> >>>>>   * struct scp_domain_data - scp domain data for power on/off flow
> >>>>> @@ -88,6 +89,8 @@
> >>>>>   * @sram_pdn_bits: The mask for sram power control bits.
> >>>>>   * @sram_pdn_ack_bits: The mask for sram power control acked bits.
> >>>>>   * @basic_clk_name: The basic clocks required by this power domain.
> >>>>> + * @subsys_clk_prefix: The prefix name of the clocks need to be enabled
> >>>>> + *                     before releasing bus protection.
> >>>>>   * @caps: The flag for active wake-up action.
> >>>>>   * @bp_table: The mask table for multiple step bus protection.
> >>>>>   */
> >>>>> @@ -98,6 +101,7 @@ struct scp_domain_data {
> >>>>>  	u32 sram_pdn_bits;
> >>>>>  	u32 sram_pdn_ack_bits;
> >>>>>  	const char *basic_clk_name[MAX_CLKS];
> >>>>> +	const char *subsys_clk_prefix;
> >>>>>  	u8 caps;
> >>>>>  	struct bus_prot bp_table[MAX_STEPS];
> >>>>>  };
> >>>>> @@ -108,6 +112,7 @@ struct scp_domain {
> >>>>>  	struct generic_pm_domain genpd;
> >>>>>  	struct scp *scp;
> >>>>>  	struct clk *clk[MAX_CLKS];
> >>>>> +	struct clk *subsys_clk[MAX_SUBSYS_CLKS];
> >>>>>  	const struct scp_domain_data *data;
> >>>>>  	struct regulator *supply;
> >>>>>  };
> >>>>> @@ -301,16 +306,22 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
> >>>>>  	val |= PWR_RST_B_BIT;
> >>>>>  	writel(val, ctl_addr);
> >>>>>  
> >>>>> -	ret = scpsys_sram_enable(scpd, ctl_addr);
> >>>>> +	ret = scpsys_clk_enable(scpd->subsys_clk, MAX_SUBSYS_CLKS);
> >>>>
> >>>> Why can't we enable the subsystem clocks together with the rest just after
> >>>> enabeling the regulator?
> >>>>
> >>>
> >>> Subsys CG could only be enabled when its own power domain is already
> >>> turned ON, and vice versa.
> >>> In the dt-binding doc we mentioned there would have two groups of
> >>> clocks.
> >>> e.g.,
> >>> BASIC clocks need to be enabled before enabling the corresponding power
> >>> domain.
> >>> SUBSYS clocks need to be enabled before releasing the bus protection.
> >>>
> >>
> >> Do I understand correctly that we could enable/disable all clocks in the same
> >> place as long as we make sure that the the basic clocks are turned on before we
> >> turn on the subsys clocks, correct?
> >>
> > 
> > simply, yes
> > 
> >> So why do we need to implement this logic in the power-controller driver?
> >> Shouldn't that be part of the common clock driver?
> >>
> > 
> > we implement the subsys clock logic here just due to we already
> > implement the bus protection flow in the power-controller driver.
> 
> I think in this driver is the correct place to implement bus protection flow.
> 
> > And If we don't enable the subsys clocks, bus protection cannot work.
> > Hence, even the subsys power is on but the HW modules under this subsys
> > power cannot access the bus though.
> 
> Ok, I understand that. But I understand that this should be fixed in the clock
> driver. It seems the clock driver does not reflect the correct clock tree.
> For example:
> clocks CLK_MM_SMI_COMMON, CLK_MM_SMI_LARB0, CLK_MM_SMI_LARB1, CLK_MM_GALS_COMM0,
> CLK_MM_GALS_COMM1, CLK_MM_GALS_CCU2MM, CLK_MM_GALS_IPU12MM, CLK_MM_GALS_IMG2MM,
> CLK_MM_GALS_CAM2MM, CLK_MM_GALS_IPU2MM need the CLK_TOP_MUX_MM to be enabled
> first. So I suppose CLK_TOP_MUX_MM is the parent clock of the other CLK_MM_*
> clocks. If the clock tree is correctly described in the clock driver, then the
> common clock framework will take care to enable CLK_TOP_MUX_MM when you try to
> enable an CLK_MM_* clocks.
> 
> Why does that not work on mt8183? My impression after a quick look into the
> clock driver is, that this should work.
> 

In fact, subsys clock registers could be controlled only when its power
domain is turned on.
So in the series[1] below, we are trying to associate the mfg subsys
clock with mfg power domain.

[1] https://patchwork.kernel.org/cover/11126157/

In other words, a complete flow when we enable a subsys clock for a
subsys H/W engine would be like following steps,
1. enable basic clocks that power domain depends on
2. enable power domain
3. enable subsys clocks that needed during bus protection process
4. release the bus protection
5. enable the target subsys engine clocks

For the mmsys, I guess we might be able to apply such change but there
is a little problem need to be solved first.
1. power controller wants to get the subsys clocks in register function
while driver probes, but it fails.
2. clock controller associates with the power domain while driver probes
and it fails too.
In the end, both power and clock controller cannot register
successfully.
But maybe just register the mmsys clocks earlier in module
initialization stage, but to associate with mm power domain during probe
would be a simple solution.

Back to your first question in this discussion, why do we need to
implement this logic in the power-controller driver?
I was thinking these subsys clock control flow should be coupled with
bus protection control.
What do you think?

> Regards,
> Matthias
> 
> > 
> >> Regards,
> >> Matthias
> >>
> >>>>>  	if (ret < 0)
> >>>>>  		goto err_pwr_ack;
> >>>>>  
> >>>>> +	ret = scpsys_sram_enable(scpd, ctl_addr);
> >>>>> +	if (ret < 0)
> >>>>> +		goto err_sram;
> >>>>> +
> >>>>>  	ret = scpsys_bus_protect_disable(scpd);
> >>>>>  	if (ret < 0)
> >>>>> -		goto err_pwr_ack;
> >>>>> +		goto err_sram;
> >>>>>  
> >>>>>  	return 0;
> >>>>>  
> >>>>> +err_sram:
> >>>>> +	scpsys_clk_disable(scpd->subsys_clk, MAX_SUBSYS_CLKS);
> >>>>>  err_pwr_ack:
> >>>>>  	scpsys_clk_disable(scpd->clk, MAX_CLKS);
> >>>>>  err_clk:
> >>>>> @@ -337,6 +348,8 @@ static int scpsys_power_off(struct generic_pm_domain *genpd)
> >>>>>  	if (ret < 0)
> >>>>>  		goto out;
> >>>>>  
> >>>>> +	scpsys_clk_disable(scpd->subsys_clk, MAX_SUBSYS_CLKS);
> >>>>> +
> >>>>
> >>>> Same here, why can't we disable the clocks in the scpsys_clk_disable call?
> >>>>
> >>>>>  	/* subsys power off */
> >>>>>  	val = readl(ctl_addr);
> >>>>>  	val |= PWR_ISO_BIT;
> >>>>> @@ -374,6 +387,48 @@ static int scpsys_power_off(struct generic_pm_domain *genpd)
> >>>>>  	return ret;
> >>>>>  }
> >>>>>  
> >>>>> +static int init_subsys_clks(struct platform_device *pdev,
> >>>>> +		const char *prefix, struct clk **clk)
> >>>>> +{
> >>>>> +	struct device_node *node = pdev->dev.of_node;
> >>>>> +	u32 prefix_len, sub_clk_cnt = 0;
> >>>>> +	struct property *prop;
> >>>>> +	const char *clk_name;
> >>>>> +
> >>>>> +	if (!node) {
> >>>>> +		dev_err(&pdev->dev, "Cannot find scpsys node: %ld\n",
> >>>>> +			PTR_ERR(node));
> >>>>> +		return PTR_ERR(node);
> >>>>> +	}
> >>>>> +
> >>>>> +	prefix_len = strlen(prefix);
> >>>>> +
> >>>>> +	of_property_for_each_string(node, "clock-names", prop, clk_name) {
> >>>>> +		if (!strncmp(clk_name, prefix, prefix_len) &&
> >>>>> +				(clk_name[prefix_len] == '-')) {
> >>>>> +			if (sub_clk_cnt >= MAX_SUBSYS_CLKS) {
> >>>>> +				dev_err(&pdev->dev,
> >>>>> +					"subsys clk out of range %d\n",
> >>>>> +					sub_clk_cnt);
> >>>>> +				return -ENOMEM;
> >>>>
> >>>> EINVAL maybe, ENOMEM seems wrong here.
> >>>>
> >>>
> >>> OK, I'll fix with correct error.
> >>>
> >>>>> +			}
> >>>>> +
> >>>>> +			clk[sub_clk_cnt] = devm_clk_get(&pdev->dev,
> >>>>> +						clk_name);
> >>>>
> >>>> Here we get hit by the bad design of this driver in the first place. As we need
> >>>> the subsystem-name (eg mm-0, mm-1) to group clocks to one scp_domain.
> >>>> I think we should better try to model the domains and subdomains in DTS and add
> >>>> their clocks to it. This way we can also get rid of the scp_subdomain which can
> >>>> hit it's limit anytime soon when we have a chip with a sub-subdomain.
> >>>> That will need a new driver, but as it seems the mt8183 and the mt6765 have a
> >>>> more complex design I think it is worth it.
> >>>>
> >>>> That said, given that you are in v11 already I understand that your motivation
> >>>> to start over isn't the biggest. The problem is, any new driver will have new
> >>>> bindings and won't work with older DTS. So adding a lot of stuff on top of a not
> >>>> really nice driver isn't something I'm very keen on. On the other hand you
> >>>> already put a lot of work into this solution.
> >>>>
> >>>> My proposal, I'll try to bake up a new driver this week. If I fail to deliver,
> >>>> it's up to you to decide if you want to go on with the approach in this series
> >>>> or try to work on the new one.
> >>>
> >>>> Regards,
> >>>> Matthias
> >>>>
> >>>
> >>> Thanks for considering our request.
> >>>
> >>>>> +
> >>>>> +			if (IS_ERR(clk[sub_clk_cnt])) {
> >>>>> +				dev_err(&pdev->dev,
> >>>>> +					"Subsys clk get fail %ld\n",
> >>>>> +					PTR_ERR(clk[sub_clk_cnt]));
> >>>>> +				return PTR_ERR(clk[sub_clk_cnt]);
> >>>>> +			}
> >>>>> +			sub_clk_cnt++;
> >>>>> +		}
> >>>>> +	}
> >>>>> +
> >>>>> +	return sub_clk_cnt;
> >>>>> +}
> >>>>> +
> >>>>>  static int init_basic_clks(struct platform_device *pdev, struct clk **clk,
> >>>>>  			const char * const *name)
> >>>>>  {
> >>>>> @@ -466,6 +521,7 @@ static struct scp *init_scp(struct platform_device *pdev,
> >>>>>  		struct scp_domain *scpd = &scp->domains[i];
> >>>>>  		struct generic_pm_domain *genpd = &scpd->genpd;
> >>>>>  		const struct scp_domain_data *data = &scp_domain_data[i];
> >>>>> +		int clk_cnt;
> >>>>
> >>>> clk_cnt sounds to me like clock count, but the variable actually is only used to
> >>>> check the return value of init_subsys_clks. Please rename it to ret or something
> >>>> like this.
> >>>>
> >>>
> >>> OK, I'll fix it.
> >>>
> >>>>>  
> >>>>>  		pd_data->domains[i] = genpd;
> >>>>>  		scpd->scp = scp;
> >>>>> @@ -476,6 +532,18 @@ static struct scp *init_scp(struct platform_device *pdev,
> >>>>>  		if (ret)
> >>>>>  			return ERR_PTR(ret);
> >>>>>  
> >>>>> +		if (data->subsys_clk_prefix) {
> >>>>> +			clk_cnt = init_subsys_clks(pdev,
> >>>>> +					data->subsys_clk_prefix,
> >>>>> +					scpd->subsys_clk);
> >>>>> +			if (clk_cnt < 0) {
> >>>>> +				dev_err(&pdev->dev,
> >>>>> +					"%s: subsys clk unavailable\n",
> >>>>> +					data->name);
> >>>>> +				return ERR_PTR(clk_cnt);
> >>>>> +			}
> >>>>> +		}
> >>>>> +
> >>>>>  		genpd->name = data->name;
> >>>>>  		genpd->power_off = scpsys_power_off;
> >>>>>  		genpd->power_on = scpsys_power_on;
> >>>>>
> >>>
> >>
> >> _______________________________________________
> >> Linux-mediatek mailing list
> >> Linux-mediatek@...ts.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-mediatek
> > 
> 
> _______________________________________________
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> Linux-mediatek@...ts.infradead.org
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