Re: [PATCH v2] drm: Add Grain Media GM12U320 kms driver

[Hans de Goede <hdegoede@redhat.com>]

Hi,

Thanks for the review!

On 03-06-16 19:27, Thierry Reding wrote:
> On Fri, Jun 03, 2016 at 03:06:32PM +0200, Hans de Goede wrote:
>> Grain-media GM12U320 based devices are mini video projectors using USB for
>> both power and video data transport.
>>
>> This commit adds a kms driver for these devices, including prime support.
>>
>> This driver is based on the existing udl kms driver, and the gm12u320
>> fb driver by Viacheslav Nurmekhamitov <slavrn@yandex.ru>.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> Changes in v2:
>> -Rebase on 4.7-rc1
>> -Sync with udl, bring in any fixes done to udl since v1
>
> This sounds a little nightmarish in the long term. From a cursory look
> this duplicates a bunch of code that's present in UDL, where the main
> differences are EDID handling and data transfer. I wonder if we can't
> find a better way of reusing code than duplicating it.

I was planning on eventually moving the shared code to some kms-usb helper
lib, I was thinking it would be good to have more then one user first,
but if people prefer me first factoring out some code from udl into
a lib I can do that instead.

>> diff --git a/drivers/gpu/drm/gm12u320/gm12u320_connector.c b/drivers/gpu/drm/gm12u320/gm12u320_connector.c
> [...]
>> +/*
>> + * Note this assumes this driver is only ever used with the Acer C120, if we
>> + * add support for other devices the vendor and model should be parameterized.
>> + */
>> +static struct edid gm12u320_edid = {
>> +	.header		= { 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00 },
>> +	.mfg_id		= { 0x04, 0x72 },	/* "ACR" */
>> +	.prod_code	= { 0x20, 0xc1 },	/* C120h */
>> +	.mfg_week	= 1,
>> +	.mfg_year	= 1,
>> +	.version	= 1,			/* EDID 1.3 */
>> +	.revision	= 3,			/* EDID 1.3 */
>> +	.input		= 0x80,			/* Digital input */
>> +	.features	= 0x02,			/* Pref timing in DTD 1 */
>> +	.standard_timings = { { 1, 1 }, { 1, 1 }, { 1, 1 }, { 1, 1 },
>> +			      { 1, 1 }, { 1, 1 }, { 1, 1 }, { 1, 1 } },
>> +	.detailed_timings = { {
>> +		.pixel_clock = 3383,
>> +		/* hactive = 852, hblank = 256 */
>> +		.data.pixel_data.hactive_lo = 0x54,
>> +		.data.pixel_data.hblank_lo = 0x00,
>> +		.data.pixel_data.hactive_hblank_hi = 0x31,
>> +		/* vactive = 480, vblank = 28 */
>> +		.data.pixel_data.vactive_lo = 0xe0,
>> +		.data.pixel_data.vblank_lo = 0x1c,
>> +		.data.pixel_data.vactive_vblank_hi = 0x10,
>> +		/* hsync offset 40 pw 128, vsync offset 1 pw 4 */
>> +		.data.pixel_data.hsync_offset_lo = 0x28,
>> +		.data.pixel_data.hsync_pulse_width_lo = 0x80,
>> +		.data.pixel_data.vsync_offset_pulse_width_lo = 0x14,
>> +		.data.pixel_data.hsync_vsync_offset_pulse_width_hi = 0x00,
>> +		/* Digital separate syncs, hsync+, vsync+ */
>> +		.data.pixel_data.misc = 0x1e,
>> +	}, {
>> +		.pixel_clock = 0,
>> +		.data.other_data.type = 0xfd, /* Monitor ranges */
>> +		.data.other_data.data.range.min_vfreq = 59,
>> +		.data.other_data.data.range.max_vfreq = 61,
>> +		.data.other_data.data.range.min_hfreq_khz = 29,
>> +		.data.other_data.data.range.max_hfreq_khz = 32,
>> +		.data.other_data.data.range.pixel_clock_mhz = 4, /* 40 MHz */
>> +		.data.other_data.data.range.flags = 0,
>> +		.data.other_data.data.range.formula.cvt = {
>> +			0xa0, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20 },
>> +	}, {
>> +		.pixel_clock = 0,
>> +		.data.other_data.type = 0xfc, /* Model string */
>> +		.data.other_data.data.str.str = {
>> +			'C', '1', '2', '0', 'P', 'r', 'o', 'j', 'e', 'c',
>> +			't', 'o', 'r' },
>> +	}, {
>> +		.pixel_clock = 0,
>> +		.data.other_data.type = 0xfe, /* Unspecified text / padding */
>> +		.data.other_data.data.str.str = {
>> +			'\n', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ',
>> +			' ', ' ',  ' ' },
>> +	} },
>> +	.checksum = 0x40,
>> +};
>
> Where did you get this from?

I completely made it up, other then for the resolution which is the native
resolution of the lcd in the projector

> Doesn't this device have a chip that you can query at runtime?

Not to my knowledge.

>> +static int gm12u320_connector_set_property(struct drm_connector *connector,
>> +					   struct drm_property *property,
>> +					   uint64_t val)
>> +{
>> +	return 0;
>> +}
>
> Just drop it if it doesn't do anything.

Ok, then it should probably be dropped from udl too, I'll check and submit
a separate patch for this.

>> +int gm12u320_connector_init(struct drm_device *dev,
>> +			    struct drm_encoder *encoder)
>> +{
>> +	struct drm_connector *connector;
>> +
>> +	connector = kzalloc(sizeof(struct drm_connector), GFP_KERNEL);
>> +	if (!connector)
>> +		return -ENOMEM;
>> +
>> +	drm_connector_init(dev, connector, &gm12u320_connector_funcs,
>> +			   DRM_MODE_CONNECTOR_Unknown);
>
> According to the Grain Media website this chip is a USB 3.0-to-HDMI
> bridge, so DRM_MODE_CONNECTOR_HDMIA might be a better choice here.

Hmm, where did you find this ? Note I've never actually verified
the gm12u320 name this comes from previous reverse engineering
work done on the projector.

HDMI for what is in essence a lcd panel seems wrong, maybe lvds
if you want to avoid Unknown ?

>> diff --git a/drivers/gpu/drm/gm12u320/gm12u320_drv.c b/drivers/gpu/drm/gm12u320/gm12u320_drv.c
> [...]
>> new file mode 100644
>> index 0000000..eff3a44
>> --- /dev/null
>> +++ b/drivers/gpu/drm/gm12u320/gm12u320_drv.c
>> @@ -0,0 +1,160 @@
>> +/*
>> + * Copyright (C) 2012-2016 Red Hat Inc.
>> + *
>> + * This file is subject to the terms and conditions of the GNU General Public
>> + * License v2. See the file COPYING in the main directory of this archive for
>> + * more details.
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <drm/drmP.h>
>> +#include <drm/drm_crtc_helper.h>
>> +#include "gm12u320_drv.h"
>> +
>> +static int gm12u320_driver_set_busid(struct drm_device *d, struct drm_master *m)
>> +{
>> +	return 0;
>> +}
>
> This is optional, you can drop it.

Idem. as above, then it should probably be dropped from udl too, I'll check and
submit a separate patch for this.

Regards,

Hans
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