linux-kernel - Re: [PATCH] Revert "phy: qualcomm: usb28nm: Add MDM9607 init sequence"

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Date:   Mon, 16 Jan 2023 21:35:49 +0100
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Michael Srba <Michael.Srba@...nam.cz>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "phy: qualcomm: usb28nm: Add MDM9607 init
 sequence"

On 2023-01-13 23:16:15, Vinod Koul wrote:
> On 14-12-22, 23:37, Marijn Suijten wrote:
> > This reverts commit 557a28811c7e0286d3816842032db5eb7bb5f156.
> > 
> > This commit introduced an init sequence from downstream DT [1] in the
> > driver.  As mentioned by the comment above the HSPHY_INIT_CFG macro for
> > this sequence:
> > 
> >     /*
> >      * The macro is used to define an initialization sequence.  Each tuple
> >      * is meant to program 'value' into phy register at 'offset' with 'delay'
> >      * in us followed.
> >      */
> > 
> > Instead of corresponding to offsets into the phy register, the sequence
> > read by the downstream driver [2] is passed into ulpi_write [3] which
> > crafts the address-value pair into a new value and writes it into the
> > same register at USB_ULPI_VIEWPORT [4].  In other words, this init
> > sequence is programmed into the hardware in a totally different way than
> > downstream and is unlikely to achieve the desired result, if the hsphy
> > is working at all.
> > 
> > An alternative method needs to be found to write these init values at
> > the desired location.  Fortunately mdm9607 did not land upstream yet [5]
> > and should have its compatible revised to use the generic one, instead
> > of a compatible that writes wrong data to the wrong registers.
> 
> Applied after adding missing subsystem tag, thanks

Thanks, it wasn't clear to me whether to suffix the title when already
included in the Revert: "phy: qualcomm: ..." title :)

- Marijn