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Date:   Wed, 15 Jun 2022 15:57:55 +0200
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Subject: Re: [PATCH v2 7/7] drm/bridge: anx7625: Add typec_mux_set callback
 function
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To:     Prashant Malani <pmalani@chromium.org>,
        Pin-yen Lin <treapking@chromium.org>
Cc:     linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        heikki.krogerus@linux.intel.com,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        David Airlie <airlied@linux.ie>,
        "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Tzung-Bi Shih <tzungbi@google.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        =?UTF-8?B?TsOtY29sYXMgRi4gUi4gQS4gUHJhZG8=?= 
        <nfraprado@collabora.com>, Jonas Karlman <jonas@kwiboo.se>,
        swboyd@chromium.org, Rob Herring <robh+dt@kernel.org>,
        Maxime Ripard <maxime@cerno.tech>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Xin Ji <xji@analogixsemi.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Robert Foss <robert.foss@linaro.org>,
        =?UTF-8?B?Sm9zw6kgRXhww7NzaXRv?= <jose.exposito89@gmail.com>
References: <20220609181106.3695103-1-pmalani@chromium.org>
 <20220609181106.3695103-8-pmalani@chromium.org>
 <1191703c-efa5-7fe6-7dd0-e3e786b58411@collabora.com>
 <CAEXTbpfh3aKS8DZ9T0KPNLfWJ4EsLxcJpP8aLYU-iQYC1N4sRQ@mail.gmail.com>
 <CACeCKafeJ40y2LYsEm4Z2pRMxzM6W+VcC1F95oFqNq+xokPWUQ@mail.gmail.com>
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
In-Reply-To: <CACeCKafeJ40y2LYsEm4Z2pRMxzM6W+VcC1F95oFqNq+xokPWUQ@mail.gmail.com>
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Il 14/06/22 18:58, Prashant Malani ha scritto:
> On Tue, Jun 14, 2022 at 2:08 AM Pin-yen Lin <treapking@chromium.org> wrote:
>>
>> Hi AngeloGioacchino,
>>
>>
>> On Tue, Jun 14, 2022 at 4:15 PM AngeloGioacchino Del Regno
>> <angelogioacchino.delregno@collabora.com> wrote:
>>>
>>> Il 09/06/22 20:09, Prashant Malani ha scritto:
>>>> From: Pin-Yen Lin <treapking@chromium.org>
>>>>
>>>> Add the callback function when the driver receives state
>>>> changes of the Type-C port. The callback function configures the
>>>> crosspoint switch of the anx7625 bridge chip, which can change the
>>>> output pins of the signals according to the port state.
>>>>
>>>> Signed-off-by: Pin-Yen Lin <treapking@chromium.org>
>>>> Signed-off-by: Prashant Malani <pmalani@chromium.org>
>>>> ---
>>>>
>>>> Changes since v2:
>>>> - No changes.
>>>>
>>>>    drivers/gpu/drm/bridge/analogix/anx7625.c | 58 +++++++++++++++++++++++
>>>>    drivers/gpu/drm/bridge/analogix/anx7625.h | 13 +++++
>>>>    2 files changed, 71 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
>>>> index d41a21103bd3..2c308d12fab2 100644
>>>> --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
>>>> +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
>>>> @@ -15,6 +15,7 @@
>>>>    #include <linux/regulator/consumer.h>
>>>>    #include <linux/slab.h>
>>>>    #include <linux/types.h>
>>>> +#include <linux/usb/typec_dp.h>
>>>>    #include <linux/usb/typec_mux.h>
>>>>    #include <linux/workqueue.h>
>>>>
>>>> @@ -2582,9 +2583,66 @@ static void anx7625_runtime_disable(void *data)
>>>>        pm_runtime_disable(data);
>>>>    }
>>>>
>>>> +static void anx7625_set_crosspoint_switch(struct anx7625_data *ctx,
>>>> +                                       enum typec_orientation orientation)
>>>> +{
>>>> +     if (orientation == TYPEC_ORIENTATION_NORMAL) {
>>>> +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_0,
>>>> +                               SW_SEL1_SSRX_RX1 | SW_SEL1_DPTX0_RX2);
>>>> +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_1,
>>>> +                               SW_SEL2_SSTX_TX1 | SW_SEL2_DPTX1_TX2);
>>>> +     } else if (orientation == TYPEC_ORIENTATION_REVERSE) {
>>>> +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_0,
>>>> +                               SW_SEL1_SSRX_RX2 | SW_SEL1_DPTX0_RX1);
>>>> +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_1,
>>>> +                               SW_SEL2_SSTX_TX2 | SW_SEL2_DPTX1_TX1);
>>>> +     }
>>>> +}
>>>> +
>>>> +static void anx7625_typec_two_ports_update(struct anx7625_data *ctx)
>>>> +{
>>>> +     if (ctx->typec_ports[0].dp_connected && ctx->typec_ports[1].dp_connected)
>>>> +             /* Both ports available, do nothing to retain the current one. */
>>>> +             return;
>>>> +     else if (ctx->typec_ports[0].dp_connected)
>>>> +             anx7625_set_crosspoint_switch(ctx, TYPEC_ORIENTATION_NORMAL);
>>>> +     else if (ctx->typec_ports[1].dp_connected)
>>>> +             anx7625_set_crosspoint_switch(ctx, TYPEC_ORIENTATION_REVERSE);
>>>> +}
>>>> +
>>>>    static int anx7625_typec_mux_set(struct typec_mux_dev *mux,
>>>>                                 struct typec_mux_state *state)
>>>>    {
>>>> +     struct anx7625_port_data *data = typec_mux_get_drvdata(mux);
>>>> +     struct anx7625_data *ctx = data->ctx;
>>>> +     struct device *dev = &ctx->client->dev;
>>>> +
>>>> +     bool old_dp_connected = (ctx->typec_ports[0].dp_connected ||
>>>> +                              ctx->typec_ports[1].dp_connected);
>>>
>>> So the old connection state is "either port0 or port1 are currently connected"...
>>>
>>>> +     bool new_dp_connected;
>>>> +
>>>> +     if (ctx->num_typec_switches == 1)
>>>> +             return 0;
>>>> +
>>>> +     dev_dbg(dev, "mux_set dp_connected: c0=%d, c1=%d\n",
>>>> +             ctx->typec_ports[0].dp_connected, ctx->typec_ports[1].dp_connected);
>>>> +
>>>> +     data->dp_connected = (state->alt && state->alt->svid == USB_TYPEC_DP_SID &&
>>>> +                           state->alt->mode == USB_TYPEC_DP_MODE);
>>>> + > + new_dp_connected = (ctx->typec_ports[0].dp_connected ||
>>>> +                         ctx->typec_ports[1].dp_connected);
>>>
>>> ...and the new connection state is the same as the old one, because I don't see
>>> anything that could ever modify it in this function's flow, until reaching this
>>> assignment.
>>
>> The typec mux driver data (`struct anx7625_port_data *data =
>> typec_mux_get_drvdata(mux)`) is set to one of the
>> `ctx->typec_ports[*]` in `anx7625_register_mode_switch` (see patch 6
>> of this series).
>>
>> So, the `data->dp_connected = ...` assignment may change the new
>> connection state.
> 
> Angelo, I think your interpretation of this logic is not accurate..
> |old_dp_connected| represents *whether* port1 or port0 has a DP
> partner connected, not that *either* of them has it.
> 
> So, this logic looks OK to me.
> 

Hello Prashant,

You're completely right: I've finally seen where this is happening, so yes
we don't know, nor care at that moment, whether data->dp_connected is port0
or port1, we assign and check 'em both again, which is actually smart.

I'm sorry for the misunderstandment - and thank you for your reply.

Feel free to add my

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Regards,
Angelo