Message-ID: <16e646ff-7bc1-4dad-9fcd-d4346c1dde96@quicinc.com>
Date: Wed, 27 Nov 2024 20:59:07 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: <neil.armstrong@...aro.org>
CC: Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        "Stephen
 Boyd" <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio
	<konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Dmitry
 Baryshkov" <dmitry.baryshkov@...aro.org>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        Bjorn Andersson <andersson@...nel.org>, Rob
 Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor
 Dooley <conor+dt@...nel.org>,
        Connor Abbott <cwabbott0@...il.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 05/11] drm/msm: adreno: add plumbing to generate
 bandwidth vote table for GMU

On 11/25/2024 1:42 PM, Neil Armstrong wrote:
> On 23/11/2024 23:46, Akhil P Oommen wrote:
>> On Sun, Nov 24, 2024 at 02:52:46AM +0530, Akhil P Oommen wrote:
>>> On Tue, Nov 19, 2024 at 06:56:40PM +0100, Neil Armstrong wrote:
>>>> The Adreno GMU Management Unit (GMU) can also scale DDR Bandwidth along
>>>> the Frequency and Power Domain level, but by default we leave the
>>>> OPP core scale the interconnect ddr path.
>>>>
>>>> In order to calculate vote values used by the GPU Management
>>>> Unit (GMU), we need to parse all the possible OPP Bandwidths and
>>>
>>> GMU expects a table of votes for each DDR frequency corners. Can we
>>> please try to figure out a way to do that? Generally, we should
>>> ensure the
>>> data that is send to GMU firmware match downstream exactly. Because,
>>> when something breaks in firmware or worst, at SoC level, it will be
>>> pretty
>>> hard to narrow down the issue. So, I prefer to be very conservative
>>> about
>>> this.
>>>
>>> KGSL keeps the ddr frequency table in the devicetree. That helps to keep
>>> the driver lean, but I am not sure if that is viable upstream.
> 
> No it's not, opp table is here for that, and we can reproduce the same
> bahaviour by parsing all the bandwidths in the opp table.
> 
>>>
>>> -Akhil.
>>>
>>>> create a vote value to be sent to the appropriate Bus Control
>>>> Modules (BCMs) declared in the GPU info struct.
>>>>
>>>> The vote array will then be used to dynamically generate the GMU
>>>> bw_table sent during the GMU power-up.
>>>>
>>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>>> ---
>>>>   drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 153 ++++++++++++++++++++++
>>>> ++++++++++++
>>>>   drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  14 ++++
>>>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.h |   1 +
>>>>   3 files changed, 168 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/
>>>> drm/msm/adreno/a6xx_gmu.c
>>>> index
>>>> 14db7376c712d19446b38152e480bd5a1e0a5198..f6814d92a4edb29ba8a34a34aabb8b2324e9c6a4 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>> @@ -9,6 +9,7 @@
>>>>   #include <linux/pm_domain.h>
>>>>   #include <linux/pm_opp.h>
>>>>   #include <soc/qcom/cmd-db.h>
>>>> +#include <soc/qcom/tcs.h>
>>>>   #include <drm/drm_gem.h>
>>>>     #include "a6xx_gpu.h"
>>>> @@ -1287,6 +1288,109 @@ static int a6xx_gmu_memory_probe(struct
>>>> a6xx_gmu *gmu)
>>>>       return 0;
>>>>   }
>>>>   +/**
>>>> + * struct bcm_db - Auxiliary data pertaining to each Bus Clock
>>>> Manager (BCM)
>>>> + * @unit: divisor used to convert bytes/sec bw value to an RPMh msg
>>>> + * @width: multiplier used to convert bytes/sec bw value to an RPMh
>>>> msg
>>>> + * @vcd: virtual clock domain that this bcm belongs to
>>>> + * @reserved: reserved field
>>>> + */
>>>> +struct bcm_db {
>>>> +    __le32 unit;
>>>> +    __le16 width;
>>>> +    u8 vcd;
>>>> +    u8 reserved;
>>>> +};
>>
>> Shouldn't this be a packed struct? It is naturally aligned, but still!
> 
> It's used as-is in the interconnecty driver, so I assume it's fine.
> 
>>
>>>> +
>>>> +static u64 bcm_div(u64 num, u32 base)
>>>> +{
>>>> +    /* Ensure that small votes aren't lost. */
>>>> +    if (num && num < base)
>>>> +        return 1;
>>>> +
>>>> +    do_div(num, base);
>>>> +
>>>> +    return num;
>>>> +}
>>>> +
>>>> +static int a6xx_gmu_rpmh_bw_votes_init(const struct a6xx_info *info,
>>>> +                       struct a6xx_gmu *gmu)
>>>> +{
>>>> +    const struct bcm_db *bcm_data[GMU_MAX_BCMS] = { 0 };
>>>> +    unsigned int bcm_index, bw_index;
>>>> +
>>>> +    /* Retrieve BCM data from cmd-db */
>>>> +    for (bcm_index = 0; bcm_index < GMU_MAX_BCMS; bcm_index++) {
>>>> +        size_t count;
>>>> +
>>>> +        /* Skip unconfigured BCM */
>>>> +        if (!info->bcm[bcm_index].name)
>>>> +            continue;
>>>> +
>>>> +        bcm_data[bcm_index] = cmd_db_read_aux_data(
>>>> +                        info->bcm[bcm_index].name,
>>>> +                        &count);
>>>> +        if (IS_ERR(bcm_data[bcm_index]))
>>>> +            return PTR_ERR(bcm_data[bcm_index]);
>>>> +
>>>> +        if (!count)
>>>> +            return -EINVAL;
>>>> +    }
>>>> +
>>>> +    /* Generate BCM votes values for each bandwidth & BCM */
>>>> +    for (bw_index = 0; bw_index < gmu->nr_gpu_bws; bw_index++) {
>>>> +        u32 *data = gmu->gpu_bw_votes[bw_index];
>>>> +        u32 bw = gmu->gpu_bw_table[bw_index];
>>>> +
>>>> +        /* Calculations loosely copied from bcm_aggregate() &
>>>> tcs_cmd_gen() */
>>>> +        for (bcm_index = 0; bcm_index < GMU_MAX_BCMS; bcm_index++) {
>>>> +            bool commit = false;
>>>> +            u64 peak, vote;
>>>> +            u16 width;
>>>> +            u32 unit;
>>>> +
>>>> +            /* Skip unconfigured BCM */
>>>> +            if (!info->bcm[bcm_index].name || !bcm_data[bcm_index])
>>>> +                continue;
>>>> +
>>>> +            if (bcm_index == GMU_MAX_BCMS - 1 ||
>>>> +                (bcm_data[bcm_index + 1] &&
>>>> +                 bcm_data[bcm_index]->vcd != bcm_data[bcm_index +
>>>> 1]->vcd))
>>>> +                commit = true;
>>>> +
>>>> +            if (!bw) {
>>>> +                data[bcm_index] = BCM_TCS_CMD(commit, false, 0, 0);
>>>> +                continue;
>>>> +            }
>>>> +
>>>> +            if (info->bcm[bcm_index].fixed) {
>>>> +                u32 perfmode = 0;
>>>> +
>>>> +                if (bw >= info->bcm[bcm_index].perfmode_bw)
>>>> +                    perfmode = info->bcm[bcm_index].perfmode;
>>>> +
>>>> +                data[bcm_index] = BCM_TCS_CMD(commit, true, 0,
>>>> perfmode);
>>>> +                continue;
>>>> +            }
>>>> +
>>>> +            /* Multiply the bandwidth by the width of the
>>>> connection */
>>>> +            width = le16_to_cpu(bcm_data[bcm_index]->width);
>>>> +            peak = bcm_div((u64)bw * width, info-
>>>> >bcm[bcm_index].buswidth);
>>>> +
>>>> +            /* Input bandwidth value is in KBps, scale the value to
>>>> BCM unit */
>>>> +            unit = le32_to_cpu(bcm_data[bcm_index]->unit);
>>>> +            vote = bcm_div(peak * 1000ULL, unit);
>>>> +
>>>> +            if (vote > BCM_TCS_CMD_VOTE_MASK)
>>>> +                vote = BCM_TCS_CMD_VOTE_MASK;
>>>> +
>>>> +            data[bcm_index] = BCM_TCS_CMD(commit, true, vote, vote);
>>>> +        }
>>>> +    }
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>>   /* Return the 'arc-level' for the given frequency */
>>>>   static unsigned int a6xx_gmu_get_arc_level(struct device *dev,
>>>>                          unsigned long freq)
>>>> @@ -1390,12 +1494,15 @@ static int
>>>> a6xx_gmu_rpmh_arc_votes_init(struct device *dev, u32 *votes,
>>>>    * The GMU votes with the RPMh for itself and on behalf of the GPU
>>>> but we need
>>>>    * to construct the list of votes on the CPU and send it over.
>>>> Query the RPMh
>>>>    * voltage levels and build the votes
>>>> + * The GMU can also vote for DDR interconnects, use the OPP
>>>> bandwidth entries
>>>> + * and BCM parameters to build the votes.
>>>>    */
>>>>     static int a6xx_gmu_rpmh_votes_init(struct a6xx_gmu *gmu)
>>>>   {
>>>>       struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu,
>>>> gmu);
>>>>       struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
>>>> +    const struct a6xx_info *info = adreno_gpu->info->a6xx;
>>>>       struct msm_gpu *gpu = &adreno_gpu->base;
>>>>       int ret;
>>>>   @@ -1407,6 +1514,10 @@ static int a6xx_gmu_rpmh_votes_init(struct
>>>> a6xx_gmu *gmu)
>>>>       ret |= a6xx_gmu_rpmh_arc_votes_init(gmu->dev, gmu->cx_arc_votes,
>>>>           gmu->gmu_freqs, gmu->nr_gmu_freqs, "cx.lvl");
>>>>   +    /* Build the interconnect votes */
>>>> +    if (adreno_gpu->info->features & ADRENO_FEAT_GMU_BW_VOTE)
>>>> +        ret |= a6xx_gmu_rpmh_bw_votes_init(info, gmu);
>>>> +
>>>>       return ret;
>>>>   }
>>>>   @@ -1442,6 +1553,38 @@ static int a6xx_gmu_build_freq_table(struct
>>>> device *dev, unsigned long *freqs,
>>>>       return index;
>>>>   }
>>>>   +static int a6xx_gmu_build_bw_table(struct device *dev, unsigned
>>>> long *bandwidths,
>>>> +        u32 size)
>>>> +{
>>>> +    int count = dev_pm_opp_get_opp_count(dev);
>>
>> I suppose this doesn't count the opps which are not supported by the
>> SKU. If we can go through *all* OPPs in the opp table irrespective of
>> the SKU, we will get something close to a full DDR bw table I mentioned
>> in the prevous mail.
> 
> It parses _all_ bandwitdh declared in the opp table, without any discard,
> so yes we're close to a full DDR table. It only lacks a few low bandwidths.
> 
Isn't opp_table->opp_list created after filtering with supported_hw bitmask?

-Akhil.
>>
>>>> +    struct dev_pm_opp *opp;
>>>> +    int i, index = 0;
>>>> +    unsigned int bandwidth = 1;
>>>> +
>>>> +    /*
>>>> +     * The OPP table doesn't contain the "off" bandwidth level so
>>>> we need to
>>>> +     * add 1 to the table size to account for it
>>>> +     */
>>>> +
>>>> +    if (WARN(count + 1 > size,
>>>> +        "The GMU bandwidth table is being truncated\n"))
>>>> +        count = size - 1;
>>>> +
>>>> +    /* Set the "off" bandwidth */
>>>> +    bandwidths[index++] = 0;
>>>> +
>>>> +    for (i = 0; i < count; i++) {
>>>> +        opp = dev_pm_opp_find_bw_ceil(dev, &bandwidth, 0);
>>>> +        if (IS_ERR(opp))
>>>> +            break;
>>>> +
>>>> +        dev_pm_opp_put(opp);
>>>> +        bandwidths[index++] = bandwidth++;
>>>> +    }
>>>> +
>>>> +    return index;
>>>> +}
>>>> +
>>>>   static int a6xx_gmu_pwrlevels_probe(struct a6xx_gmu *gmu)
>>>>   {
>>>>       struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu,
>>>> gmu);
>>>> @@ -1472,6 +1615,16 @@ static int a6xx_gmu_pwrlevels_probe(struct
>>>> a6xx_gmu *gmu)
>>>>         gmu->current_perf_index = gmu->nr_gpu_freqs - 1;
>>>>   +    /*
>>>> +     * The GMU also handles GPU Interconnect Votes so build a list
>>>> +     * of DDR bandwidths from the GPU OPP table
>>>> +     */
>>>> +    if (adreno_gpu->info->features & ADRENO_FEAT_GMU_BW_VOTE)
>>>> +        gmu->nr_gpu_bws = a6xx_gmu_build_bw_table(&gpu->pdev->dev,
>>>> +            gmu->gpu_bw_table, ARRAY_SIZE(gmu->gpu_bw_table));
>>>> +
>>>> +    gmu->current_perf_index = gmu->nr_gpu_freqs - 1;
>>
>> duplicate line.
>>
>>>> +
>>>>       /* Build the list of RPMh votes that we'll send to the GMU */
>>>>       return a6xx_gmu_rpmh_votes_init(gmu);
>>>>   }
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/
>>>> drm/msm/adreno/a6xx_gmu.h
>>>> index
>>>> b4a79f88ccf45cfe651c86d2a9da39541c5772b3..03603eadc0f9ed866899c95e99f333a511ebc3c1 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
>>>> @@ -19,6 +19,16 @@ struct a6xx_gmu_bo {
>>>>       u64 iova;
>>>>   };
>>>>   +#define GMU_MAX_BCMS    3
>>>> +
>>>> +struct a6xx_bcm {
>>>> +    char *name;
>>>> +    unsigned int buswidth;
>>>> +    bool fixed;
>>>> +    unsigned int perfmode;
>>>> +    unsigned int perfmode_bw;
>>>> +};
>>>> +
>>>>   /*
>>>>    * These define the different GMU wake up options - these define
>>>> how both the
>>>>    * CPU and the GMU bring up the hardware
>>>> @@ -82,6 +92,10 @@ struct a6xx_gmu {
>>>>       unsigned long gpu_freqs[16];
>>>>       u32 gx_arc_votes[16];
>>>>   +    int nr_gpu_bws;
>>>> +    unsigned long gpu_bw_table[16];
>>>> +    u32 gpu_bw_votes[16][GMU_MAX_BCMS];
>>>> +
>>>>       int nr_gmu_freqs;
>>>>       unsigned long gmu_freqs[4];
>>>>       u32 cx_arc_votes[4];
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h b/drivers/gpu/
>>>> drm/msm/adreno/a6xx_gpu.h
>>>> index
>>>> 4aceffb6aae89c781facc2a6e4a82b20b341b6cb..5b80919e595fa1ba0a3afcca55feb89e60870cb1 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>>>> @@ -44,6 +44,7 @@ struct a6xx_info {
>>>>       u32 gmu_chipid;
>>>>       u32 gmu_cgc_mode;
>>>>       u32 prim_fifo_threshold;
>>>> +    const struct a6xx_bcm bcm[GMU_MAX_BCMS];
>>
>> This table is duplicated a lot. Lets keep a pointer instead. We can
>> probably use
>> this pointer as a flag to check for GMU_IB_VOTE support too.
> 
> It's partially duplicated, basically only the permode bits and level is
> different.
> 
> We can move it out when we support more GPUs with this feature.
> 
> Neil
> 
>>
>> -Akhil
>>
>>>>   };
>>>>     struct a6xx_gpu {
>>>>
>>>> -- 
>>>> 2.34.1
>>>>
> 

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