by AngeloGioacchino Del Regno

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Subject: Re: [PATCH v2 7/7] drm/bridge: anx7625: Add typec_mux_set callback function

Il 14/06/22 18:58, Prashant Malani ha scritto:
> On Tue, Jun 14, 2022 at 2:08 AM Pin-yen Lin <[email protected]> wrote:
>>
>> Hi AngeloGioacchino,
>>
>>
>> On Tue, Jun 14, 2022 at 4:15 PM AngeloGioacchino Del Regno
>> <[email protected]> wrote:
>>>
>>> Il 09/06/22 20:09, Prashant Malani ha scritto:
>>>> From: Pin-Yen Lin <[email protected]>
>>>>
>>>> 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 <[email protected]>
>>>> Signed-off-by: Prashant Malani <[email protected]>
>>>> ---
>>>>
>>>> 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 <[email protected]>

Regards,
Angelo

2022-06-15 17:04:24

by Prashant Malani

[permalink] [raw]

Subject: Re: [PATCH v2 6/7] drm/bridge: anx7625: Register Type-C mode switches

On Wed, Jun 15, 2022 at 1:45 AM AngeloGioacchino Del Regno
<[email protected]> wrote:
>
> Il 14/06/22 18:57, Prashant Malani ha scritto:
> > On Tue, Jun 14, 2022 at 1:18 AM AngeloGioacchino Del Regno
> > <[email protected]> wrote:
> >>
> >> Il 09/06/22 20:09, Prashant Malani ha scritto:
> >>> When the DT node has "switches" available, register a Type-C mode-switch
> >>> for each listed "switch". This allows the driver to receive state
> >>> information about what operating mode a Type-C port and its connected
> >>> peripherals are in, as well as status information (like VDOs) related to
> >>> that state.
> >>>
> >>> The callback function is currently a stub, but subsequent patches will
> >>> implement the required functionality.
> >>>
> >>> Signed-off-by: Prashant Malani <[email protected]>
> >>> ---
> >>>
> >>> Changes since v2:
> >>> - No changes.
> >>>
> >>> drivers/gpu/drm/bridge/analogix/anx7625.c | 73 +++++++++++++++++++++++
> >>> drivers/gpu/drm/bridge/analogix/anx7625.h | 6 ++
> >>> 2 files changed, 79 insertions(+)
> >>>
> >>> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> >>> index 07ed44c6b839..d41a21103bd3 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_mux.h>
> >>> #include <linux/workqueue.h>
> >>>
> >>> #include <linux/of_gpio.h>
> >>> @@ -2581,9 +2582,59 @@ static void anx7625_runtime_disable(void *data)
> >>> pm_runtime_disable(data);
> >>> }
> >>>
> >>> +static int anx7625_typec_mux_set(struct typec_mux_dev *mux,
> >>> + struct typec_mux_state *state)
> >>> +{
> >>> + return 0;
> >>> +}
> >>> +
> >>> +static int anx7625_register_mode_switch(struct device *dev, struct device_node *node,
> >>> + struct anx7625_data *ctx)
> >>> +{
> >>> + struct anx7625_port_data *port_data;
> >>> + struct typec_mux_desc mux_desc = {};
> >>> + char name[32];
> >>> + u32 port_num;
> >>> + int ret;
> >>> +
> >>> + ret = of_property_read_u32(node, "reg", &port_num);
> >>> + if (ret)
> >>> + return ret;
> >>> +
> >>> + if (port_num >= ctx->num_typec_switches) {
> >>> + dev_err(dev, "Invalid port number specified: %d\n", port_num);
> >>> + return -EINVAL;
> >>> + }
> >>> +
> >>> + port_data = &ctx->typec_ports[port_num];
> >>> + port_data->ctx = ctx;
> >>> + mux_desc.fwnode = &node->fwnode;
> >>> + mux_desc.drvdata = port_data;
> >>> + snprintf(name, sizeof(name), "%s-%u", node->name, port_num);
> >>> + mux_desc.name = name;
> >>> + mux_desc.set = anx7625_typec_mux_set;
> >>> +
> >>> + port_data->typec_mux = typec_mux_register(dev, &mux_desc);
> >>> + if (IS_ERR(port_data->typec_mux)) {
> >>> + ret = PTR_ERR(port_data->typec_mux);
> >>> + dev_err(dev, "Mode switch register for port %d failed: %d", port_num, ret);
> >>> + }
> >>
> >> Please return 0 at the end of this function.
> >>
> >> if (IS_ERR(....)) {
> >> ......code......
> >> return ret;
> >> }
> >>
> >> return 0;
> >> }
> >
> > May I ask why? We're not missing any return paths. I would rather we
> > keep it as is (which has the valid return value).
> >
>
> I know that you're not missing any return paths.
>
> That's only because the proposed one is a common pattern in the kernel
> and it's only for consistency.

Thanks for the additional details. Since this isn't addressing any
specific bug, and I
notice varied usages of "return ret" in this file itself [1][2], I'd
prefer keeping it as is.

[1]: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix/anx7625.c#L296
[2]: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix/anx7625.c#L436

>
> Regards,
> Angelo
>