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 17:11:55 +0000
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...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 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.

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.

---
bod