linux-kernel - Re: [PATCH v4 3/6] media: qcom: camss: csiphy-3ph: Add Gen2 v1.1 two-phase MIPI CSI-2 DPHY init

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Date:   Thu, 9 Nov 2023 20:24:39 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        hverkuil-cisco@...all.nl, laurent.pinchart@...asonboard.com,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Robert Foss <rfoss@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, vincent.knecht@...loo.org,
        matti.lehtimaki@...il.com, quic_grosikop@...cinc.com
Cc:     linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/6] media: qcom: camss: csiphy-3ph: Add Gen2 v1.1
 two-phase MIPI CSI-2 DPHY init



On 11/9/23 18:11, Bryan O'Donoghue wrote:
> On 09/11/2023 13:55, Konrad Dybcio wrote:
>>
>>
>> On 11/9/23 12:30, Bryan O'Donoghue wrote:
>>> Add a PHY configuration sequence for the sc8280xp which uses a Qualcomm
>>> Gen 2 version 1.1 CSI-2 PHY.
>>>
>>> The PHY can be configured as two phase or three phase in C-PHY or D-PHY
>>> mode. This configuration supports two-phase D-PHY mode.
>>>
>>> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>>> ---
>> Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>
>> Aside from initialization, looks like the reset seq should be more
>> complex:
>>
>> https://git.codelinaro.org/clo/la/platform/vendor/opensource/camera-kernel/-/blob/LA.AU.1.3.7-02900-gen3_gvmgh.0/drivers/cam_sensor_module/cam_csiphy/include/cam_csiphy_1_1_hwreg.h?ref_type=tags#L39-45
>>
>> https://git.codelinaro.org/clo/la/platform/vendor/opensource/camera-kernel/-/blob/LA.AU.1.3.7-02900-gen3_gvmgh.0/drivers/cam_sensor_module/cam_csiphy/cam_csiphy_core.c#L133-154
>>
>> similarly for the "common regs" that seem to extend the init seq
>>
>> https://git.codelinaro.org/clo/la/platform/vendor/opensource/camera-kernel/-/blob/LA.AU.1.3.7-02900-gen3_gvmgh.0/drivers/cam_sensor_module/cam_csiphy/cam_csiphy_core.c#L491-527
>>
>> Konrad
> 
> So..
> 
> https://git.codelinaro.org/clo/la/platform/vendor/opensource/camera-kernel/-/blob/LA.AU.1.3.7-02900-gen3_gvmgh.0/drivers/cam_sensor_module/cam_csiphy/include/cam_csiphy_1_1_hwreg.h?ref_type=tags#L39
> 
> static struct csiphy_reg_t csiphy_reset_reg_1_1[] = {
>      {0x0814, 0x00, 0x05, CSIPHY_LANE_ENABLE}, // this is interesting
>                                                    // powers off lanemask
>                                                    // seems like a good
>                                                    // idea to me
>      {0x0818, 0x00, 0x00, CSIPHY_DEFAULT_PARAMS}, [1]
>      {0x081C, 0x00, 0x00, CSIPHY_DEFAULT_PARAMS}, [2]
>      {0x0800, 0x01, 0x01, CSIPHY_DEFAULT_PARAMS}, // this we already
>      {0x0800, 0x00, 0x00, CSIPHY_DEFAULT_PARAMS}, // do right now
> };
> 
> [1] [2] I don't see why you need that and I'd imagine the reset drives these values to zero anyway.. it should as I read the reg docs, I'd guess this is a reset sequence that comes out of a Si test bench.
Since it's there on shipped devices, I'd skew towards including it, maybe some
chips with this block had an erratum wrt the reset value


> 
> The 0x814 warrants an investigation - i.e. can we add it across platforms without breaking existing setups.
> 
> I'll kick that to a separate - one LOC "series", so we can take our time validating if it has any unexpected side-effects across our various platforms.
Sure, that's what I had in mind

Konrad