Re: [PATCH v3 05/11] drm/bridge: Add Analogix anx6345 support

[Andrzej Hajda <a.hajda@samsung.com>]

On 15.02.2019 20:36, Vasily Khoruzhick wrote:
> On Fri, Feb 15, 2019 at 1:13 AM Andrzej Hajda <a.hajda@samsung.com> wrote:
>
> Hi Andrzej,
>
> Thanks for review!
>
>>> +#include <linux/of_gpio.h>
>> Do you need this header?
> I'll drop it.
>
>>> +#include <drm/drmP.h>
>> drmP.h is/should be deprecated.
> Same here
>
>>> +struct anx6345_platform_data {
>>> +     struct regulator *dvdd12;
>>> +     struct regulator *dvdd25;
>>> +     struct gpio_desc *gpiod_reset;
>>> +};
>> Why do you need this struct, why just do not embed it's fields directly
>> into struct anx6345 ?
> OK, I'll embed it into struct anx6345
>
>>> +     if (WARN_ON(anx6345->powered))
>>> +             return;
>> It should not happen, you can remove this warn.
> OK
>
>>> +     if (pdata->dvdd12) {
>> If regulators are required this will be never null.
> Right, and regulator subsystem will return dummy regulator if it's
> missing in dts.
> I'll remove redundant checks.
>
>>> +
>>> +     if (pdata->dvdd25) {
>> ditto
> OK
>
>>> +
>>> +     if (anx6345->panel)
>>> +             drm_panel_prepare(anx6345->panel);
>> again, here and below: panel is never null, check can be removed.
> That's not true, panel is optional. It can be DP connector, not a panel.
>
>>> +
>>> +     gpiod_set_value_cansleep(pdata->gpiod_reset, 0);
>>> +     usleep_range(1000, 2000);
>>> +
>>> +     gpiod_set_value_cansleep(pdata->gpiod_reset, 1);
>>
>> Start/stop sequence seems odd regarding reset gpio:
>>
>> 1. In probe reset is set to low, in poweroff to high - incosistent.
>>
>> 2. If in case of disabled device reset should be 0, there is no point to
>> set it again to 0 three lines above.
>>
>> 3. I suspect in dts reset gpio should be declared as active_low, and the
>> logic in the driver should be reverted, in power off it should be set to
>> high, in power on it should be lowered (logically).
> OK, I'll look into it.
>
>>> +err_poweroff:
>>> +     DRM_ERROR("Failed DisplayPort transmitter initialization: %d\n", err);
>> redundant message
> OK, will drop.
>
>>> +             DRM_ERROR("Get sink count failed %d\n", err);
>> The rule of thumb I heard is that if you start message capitalized you
>> should end with dot. Since I do not know if it is enforced in kernel I
>> leave the decision up to you.
> I grepped DRM_ERROR in driver/gpu/drm and they do exactly the same as here.
> So I'll just keep it as is for consistency.
>
>>> +static bool anx6345_bridge_mode_fixup(struct drm_bridge *bridge,
>>> +                                   const struct drm_display_mode *mode,
>>> +                                   struct drm_display_mode *adjusted_mode)
>>> +{
>>> +     if (mode->flags & DRM_MODE_FLAG_INTERLACE)
>>> +             return false;
>>> +
>>> +     /* Max 1200p at 5.4 Ghz, one lane */
>>> +     if (mode->clock > 154000)
>>> +             return false;
>> These checks should be in mode_valid callback.
> OK
>
>>> +     /* Map slave addresses of ANX6345 */
>>> +     for (i = 0; i < I2C_NUM_ADDRESSES; i++) {
>>> +             if (anx6345_i2c_addresses[i] >> 1 != client->addr)
>>> +                     anx6345->i2c_clients[i] = i2c_new_dummy(client->adapter,
>>> +                                             anx6345_i2c_addresses[i] >> 1);
>>> +             else
>>> +                     anx6345->i2c_clients[i] = client;
>>
>> I see this contredanse is copy/pasted from anx78*, but it looks quite
>> complicated. As I understand there are two i2c addresses, why we cannot
>> assume one address is for control interfaces and another  is dummy? It would
>> simplify the code here and in other places.
> Sorry, I don't get you, could you elaborate? Note that anx6345 uses
> both addresses,
> i2c_new_dummy() just registers new i2c device bound to a dummy driver and it's
> supposed to be used for devices that consume more than one i2c address.


My idea was to assume that ANALOGIX_I2C_DPTX is the main address, ie.
address which should be set in dts in device node reg property.

Other addresses should be registered as dummy devices during probe -
simple loop without conditionals, without redundant fields in anx6345
context - i2c_clients, client.

I do not insist on this change but I suggest as it should simplify the code.

And moreover, you can consider removing direction bit from i2c
addresses, it could be also confusing and against i2c kernel api.

>
>>> +     if (!found) {
>>> +             DRM_ERROR("ANX%x (ver. %d) not supported by this driver\n",
>>> +                       anx6345->chipid, version);
>>> +             err = -ENODEV;
>>> +             goto err_poweroff;
>>> +     }
>>
>> As I see chip becomes powered forever, is it OK? Usually it should be
>> powered only when pipeline starts, and powered-off after pipeline stops.
> I'll look into how hard it would be to implement but personally I
> think it's OK for now.
> We can add more sophisticated power management once this driver is merged.


But the rule is every resource allocated/set during lifetime of the
driver should be dropped on driver removal, so please do it at least in
remove callback.


Regards

Andrzej





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