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Subject: Re: [PATCH v3 1/3] remoteproc: qcom: Embed private data structure for
 hexagon dsp.
To: Bjorn Andersson <bjorn.andersson@linaro.org>
References: <1478522240-11036-1-git-send-email-akdwived@codeaurora.org>
 <1478522240-11036-2-git-send-email-akdwived@codeaurora.org>
 <20161108070805.GL25787@tuxbot>
 <c5f03abe-866d-9624-eb69-166c39810b8f@codeaurora.org>
 <20161118185708.GK28340@tuxbot>
Cc: linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org,
        linux-arm-msm@vger.kernel.org
From: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>
Message-ID: <525c1d99-a8a1-70cc-0cb7-914a118f13be@codeaurora.org>
Date: Tue, 22 Nov 2016 00:46:56 +0530
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On 11/19/2016 12:27 AM, Bjorn Andersson wrote:
> On Wed 16 Nov 06:41 PST 2016, Avaneesh Kumar Dwivedi wrote:
>
>> i have been a little delayed for posting replies to patch comments,
>> hopefully onward it should be quick and fast.
>>
> I would greatly appreciate if you allow for a discussion before posting
> new revisions of the patchset. I will respond to your comments here and
> ignore v4 for now.

Ok, i will resend v4 patches with modification after consensus.
>
>> On 11/8/2016 12:38 PM, Bjorn Andersson wrote:
>>> On Mon 07 Nov 04:37 PST 2016, Avaneesh Kumar Dwivedi wrote:
> [..]
>>>> +char *active_8x96_clk_str[] = {"iface", "bus", "mem", "gpll0_mss_clk",
>>>> +		"snoc_axi_clk", "mnoc_axi_clk"};
>>> All these needs to be static, but I would prefer if you just put the
>>> values directly into the resource structs below.
>> If i have to initialize directly into resource struct, i need to declare
>> individual elements as array of fixed size
>> but number of resource lets say  number of proxy regulator not being same
>> for different q6 chips, made me to
>> work with double pointer which can be assigned with address of an array of
>> string pointer as per need when new version need to be supported.
>>
> Using a termination sentinel to indicate end of lists is quite common in
> the kernel, so you can do this:
>
> 	.active_clks = (char*[]){
> 		"iface",
> 		"bus",
> 		...,
> 		NULL
> 	},
OK
>
>> Though i have made above elements as static in next patch.
>>>> +
>>>> +static const struct q6_rproc_res msm_8996_res = {
>>>> +	.proxy_clks = proxy_8x96_clk_str,
>>>> +	.proxy_clk_cnt = 3,
>>> It's common practice to use a NULL terminator in the definition list
>>> rather than keeping separate count of the number of items.
>>>
>>> While acquiring the resources you would have to "calculate" the number
>>> and store it in the q6v5 struct, but this would make turn this struct
>>> into something only used during probe() - which is nice.
>> Yes, have modified as per suggestion.
>>>> +	.active_clks = active_8x96_clk_str,
>>>> +	.active_clk_cnt = 6,
>>>> +	.proxy_regs = proxy_8x96_reg_str,
>>>> +	.active_regs = NULL,
>>>> +	.proxy_reg_action = (int **)proxy_8x96_reg_action,
>>>> +	.proxy_reg_load = (int *)proxy_8x96_reg_load,
>>>> +	.active_reg_action = NULL,
>>>> +	.active_reg_load = NULL,
>>>> +	.proxy_reg_voltage = (int *)proxy_8x96_reg_min_voltage,
>>>> +	.active_reg_voltage = NULL,
>>>> +	.proxy_reg_cnt = 3,
>>>> +	.active_reg_cnt = 0,
>>>> +	.q6_reset_init = q6v56_init_reset,
>>>> +	.q6_version = "v56",
>>> q6_version would be better to have as a enum.
>> have removed this entry.
>> each class of q6 lets say "v56" have again many version of hexagon with
>> minor differences wrt each other.
> Okay, I'm fine with us sticking to classes, but I would like for them to
> make sense - and be listed as an enum instead of a string, to simplify
> the code.
OK, i will use one compatible string for each msm platform with enum 
denoting the class and version of hexagon chip.  something like

.compatible = "qcom,q6v56-1-5-pil", for msm 8996?
and version will carry a unique enum value based on compatible.


>
>> for example msm8996 use "v56" 1.5.0 while MSM8952 uses 1.8.0, reset sequence
> In msm-3.18 8996 is listed to be v55.
The version and class that i am referring are strictly as per HPG.
for 8996,  hexagon core for MSS is "v56" with version 1.5.0
>
>> and some other operation differ wrt to this version in terms of order of
>> register programming. so i have introduced one variable in q6v5 struct per
>> q6 chip supported, if this is defined then we can check and carry out
>> version specific instruction.
>> will this be OK?
>>
> Generally in the Linux kernel it's frowned upon to carry the version
> information and then do conditional operation on this.
OK
>
> It's preferred to carry explicit flags through the implementation, e.g.
> carrying "mba.mbn" vs "mba.b00" rather than switching based on "version"
> at the point of use of this data.
If i have one enum for each version (which will require one compatible 
for each platform) then i can easily pass firmware binary name to probe.
> But I'm not sure if the other differences has reasonable names, e.g. how
> to we denote the differences in reset sequence?
  i have one option that should initialize one function pointer for each 
compatible to perform reset sequence, but this way there will be huge 
duplicity of code as more than 50% code in reset sequence remain same, 
else based on check something like below i can perform certain unique 
register operations for a particular hexagon core.

if (drvdata->hexagon_flag & 0x2)
     do this
else
     do that

where hexagon_flag will be initialized with enum based on compatible.??
>
>>>> +	.q6_mba_image = "mba.mbn",
>>>> +};
>>>> +
>>>> +char *proxy_8x16_reg_str[] = {"mx", "cx", "pll"};
>>>> +char *active_8x16_reg_str[] = {"mss"};
>>>> +int  proxy_8x16_reg_action[4][2] = { {0, 1}, {1, 0}, {1, 0} };
>>>> +int  active_8x16_reg_action[1][2] = { {1, 1} };
>>>> +int  proxy_8x16_reg_load[] = {100000, 0, 100000, 100000};
>>>> +int  active_8x16_reg_load[] = {100000};
>>>> +int  proxy_8x16_reg_min_voltage[] = {1050000, 0, 0};
>>>> +int  active_8x16_reg_min_voltage[] = {1000000};
>>>> +char *proxy_8x16_clk_str[] = {"xo"};
>>>> +char *active_8x16_clk_str[] = {"iface", "bus", "mem"};
>>>> +
>>>> +static const struct q6_rproc_res msm_8916_res = {
>>>> +	.proxy_clks = proxy_8x16_clk_str,
>>>> +	.proxy_clk_cnt = 1,
>>>> +	.active_clks = active_8x16_clk_str,
>>>> +	.active_clk_cnt = 3,
>>>> +	.proxy_regs = proxy_8x16_reg_str,
>>>> +	.active_regs = active_8x16_reg_str,
>>>> +	.proxy_reg_action = (int **)proxy_8x16_reg_action,
>>>> +	.proxy_reg_load = (int *)proxy_8x16_reg_load,
>>>> +	.active_reg_action = (int **)active_8x16_reg_action,
>>>> +	.active_reg_load = (int *)active_8x16_reg_load,
>>>> +	.proxy_reg_voltage = (int *)proxy_8x16_reg_min_voltage,
>>>> +	.active_reg_voltage = active_8x16_reg_min_voltage,
>>>> +	.proxy_reg_cnt = 3,
>>>> +	.active_reg_cnt = 1,
>>>> +	.q6_reset_init = q6v5_init_reset,
>>>> +	.q6_version = "v5",
>>>> +	.q6_mba_image = "mba.b00",
>>> q6v55 (msm8916) also uses mba.mbn, while q6v5 (msm8974) uses mba.b00.
>> Again this is a case where compatible string can not help, we should have
>> single compatible string i.e. "q6v5" for msm8916 and msm8974 since both are
>> from same class of q6 chip with different version.
>> so if we cant initialize mdt name based on compatible string alone.
> msm-3.4, msm-3.10 and msm-3.18 states that they are not the same and as
> such I don't think we have a problem.
>
> The more I look at this, the more convinced I am that we got 8916 wrong,
> i.e. we specified the wrong class and it just happens to work.
>
>>>> +};
>>>> +
>>>> +static const struct of_device_id q6_of_match[] = {
>>>> +	{ .compatible = "qcom,q6v5-pil", .data = &msm_8916_res},
>>> As I was looking in the CAF tree, I believe the correct version for 8916
>>> is 5.5 and v5 was used in 8974.
>>>
>>> But I presume these versions are not strictly tied to certain platforms,
>>> so please name the resource structs based on the q6v5 version, rather
>>> than platforms.
>> Yes, resource are tied to compatible and version of q6.
>> have used compatible to initialize major resources but using DT specified
>> version string for minor deviations where needed.
>> Should this be fine?
>> as far as version on 8916 and 8974 are concern they are as below.
>>
>> msm8974 q6v5 core version  5.0.0
>> msm8916 q6v5 core version  5.1.1
> If there are differences within a class then that just forces us to use
> the version number. There's very little overhead in carrying one
> compatible per platform, if that's what we need.

Yes i will use one compatible per msm platform.
>
>>>> +	{ .compatible = "qcom,q6v56-pil", .data = &msm_8996_res},
>>>>   	{ },
>>>>   };
> Regards,
> Bjorn