Message-ID: <85977827-5f17-4071-a8a5-adefadce0ca2@linaro.org>
Date: Wed, 27 Nov 2024 16:47:14 +0100
From: neil.armstrong@...aro.org
To: Akhil P Oommen <quic_akhilpo@...cinc.com>
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 27/11/2024 16:29, Akhil P Oommen wrote:
> 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?

Sure, but opp filtering is not supported on a7xx, and nevetheless only
the high OPPs would be filtered out, so I don't understand why it would matter ?

As of today, the gx_arc_votes are already constructed the exact same way
I build the BW vote table, so why the BW table should be the ____exact____
same as downstream while we don't care about the gx_arc_votes ?

Neil

> 
> -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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