linux-kernel - Re: [PATCH 2/2] phy: qcom-qmp: new qmp phy driver for qcom-chipsets

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Date:   Tue, 22 Nov 2016 13:17:52 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     "robh+dt" <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] phy: qcom-qmp: new qmp phy driver for qcom-chipsets

Hi Kishon,


On Thu, Nov 10, 2016 at 2:33 PM, Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
> Hi Kishon,
>

>>> +unsigned int msm8996_pciephy_tx_offsets[] = { 0x1000, 0x2000, 0x3000 };
>>> +unsigned int msm8996_pciephy_rx_offsets[] = { 0x1200, 0x2200, 0x3200 };
>>> +unsigned int msm8996_pciephy_pcs_offsets[] = { 0x1400, 0x2400, 0x3400 };

>> you can have a separate reg map for each lane and all these can come from dt.
>
> The idea is to avoid the any child nodes for lanes. So, we have the complete
> ioremaped region and these offsets to tx, rx and pcs blocks.

I don't see benefits in using regmap for different lanes.
Do you see benefits in replacing a bunch of readl()/writel() with
regmap_read()/regmap_update_bits()/regmap_write() ?

I can as well use separate 'reg' values for each lanes, and have the offsets
come from dt. Something like below :

 - reg: array of offset and length of the PHY register sets.
       at index 0: offset and length of register set for PHY common
                   serdes block.
       from index 1 - N: offset and length of register set for each lane,
                         for N number of phy lanes (ports).
 - lane-offsets: array of offsets to tx, rx and pcs blocks for phy lanes.

Example:
       pcie_phy: pciephy@...00 {
               compatible = "qcom,msm8996-qmp-pcie-phy";
               reg = <0x034000 0x48f>,
                       <0x035000 5bf>,
                       <0x036000 5bf>,
                       <0x037000 5bf>;
                                       /* tx, rx, pcs */
               lane-offsets = <0x0 0x200 0x400>;


Does this look OK ? Or should i use regmap only ?


Thanks
Vivek
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