Message-ID: <ZIaRoTHar/s5yZAh@nixie71>
Date:   Sun, 11 Jun 2023 22:31:45 -0500
From:   Jeff LaBundy <jeff@...undy.com>
To:     Neil Armstrong <neil.armstrong@...aro.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Hans de Goede <hdegoede@...hat.com>,
        Henrik Rydberg <rydberg@...math.org>,
        linux-input@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 4/4] input: touchscreen: add SPI support for Goodix
 Berlin Touchscreen IC

Hi Neil,

On Tue, Jun 06, 2023 at 04:31:59PM +0200, Neil Armstrong wrote:
> Add initial support for the new Goodix "Berlin" touchscreen ICs
> over the SPI interface.
> 
> The driver doesn't use the regmap_spi code since the SPI messages
> needs to be prefixed, thus this custom regmap code.
> 
> This initial driver is derived from the Goodix goodix_ts_berlin
> available at [1] and [2] and only supports the GT9916 IC
> present on the Qualcomm SM8550 MTP & QRD touch panel.
> 
> The current implementation only supports BerlinD, aka GT9916.
> 
> [1] https://github.com/goodix/goodix_ts_berlin
> [2] https://git.codelinaro.org/clo/la/platform/vendor/opensource/touch-drivers
> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  drivers/input/touchscreen/Kconfig             |  14 ++
>  drivers/input/touchscreen/Makefile            |   1 +
>  drivers/input/touchscreen/goodix_berlin_spi.c | 183 ++++++++++++++++++++++++++
>  3 files changed, 198 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index da6d5d75c42d..ffe0c0a4cd15 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -435,6 +435,20 @@ config TOUCHSCREEN_GOODIX_BERLIN_I2C
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called goodix_berlin_i2c.
>  
> +config TOUCHSCREEN_GOODIX_BERLIN_SPI
> +	tristate "Goodix Berlin SPI touchscreen"
> +	depends on SPI_MASTER
> +	depends on REGMAP

As TOUCHSCREEN_GOODIX_BERLIN_CORE already depends on REGMAP; is this
line necessary?

I was about to ask why not to select REGMAP_SPI; thank you for the
additional information in the commit message.

> +	select TOUCHSCREEN_GOODIX_BERLIN_CORE
> +	help
> +	  Say Y here if you have the a touchscreen connected to your
> +	  system using the Goodix Berlin IC connection via SPI.

Same comment here with regard to diction.

> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called goodix_berlin_spi.
> +
>  config TOUCHSCREEN_HIDEEP
>  	tristate "HiDeep Touch IC"
>  	depends on I2C
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 921a2da0c2be..29524e8a83db 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -49,6 +49,7 @@ obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_CORE)	+= goodix_berlin_core.o
>  obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_I2C)	+= goodix_berlin_i2c.o
> +obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_SPI)	+= goodix_berlin_spi.o
>  obj-$(CONFIG_TOUCHSCREEN_HIDEEP)	+= hideep.o
>  obj-$(CONFIG_TOUCHSCREEN_HYNITRON_CSTXXX)	+= hynitron_cstxxx.o
>  obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
> diff --git a/drivers/input/touchscreen/goodix_berlin_spi.c b/drivers/input/touchscreen/goodix_berlin_spi.c
> new file mode 100644
> index 000000000000..0f4f650fdf3f
> --- /dev/null
> +++ b/drivers/input/touchscreen/goodix_berlin_spi.c
> @@ -0,0 +1,183 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Goodix Berlin Touchscreen Driver
> + *
> + * Copyright (C) 2020 - 2021 Goodix, Inc.
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Based on goodix_ts_berlin driver.
> + */
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/regmap.h>

Please alphabetize these to aid readability.

> +#include <asm/unaligned.h>
> +
> +#include "goodix_berlin.h"
> +
> +#define SPI_TRANS_PREFIX_LEN	1
> +#define REGISTER_WIDTH		4
> +#define SPI_READ_DUMMY_LEN	3
> +#define SPI_READ_PREFIX_LEN	(SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH + SPI_READ_DUMMY_LEN)
> +#define SPI_WRITE_PREFIX_LEN	(SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH)
> +
> +#define SPI_WRITE_FLAG		0xF0
> +#define SPI_READ_FLAG		0xF1
> +
> +static int goodix_berlin_spi_read(void *context, const void *reg_buf,
> +				  size_t reg_size, void *val_buf,
> +				  size_t val_size)
> +{
> +	struct spi_device *spi = context;
> +	struct spi_transfer xfers;
> +	struct spi_message spi_msg;
> +	const u32 *reg = reg_buf; /* reg is stored as native u32 at start of buffer */
> +	u8 *buf = NULL;
> +	int ret = 0;

No need to initialize these, only to forcibly assign them later.

> +
> +	if (reg_size != REGISTER_WIDTH)
> +		return -EINVAL;
> +
> +	buf = kzalloc(SPI_READ_PREFIX_LEN + val_size, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	spi_message_init(&spi_msg);
> +	memset(&xfers, 0, sizeof(xfers));
> +
> +	/* buffer format: 0xF1 + addr(4bytes) + dummy(3bytes) + data */
> +	buf[0] = SPI_READ_FLAG;
> +	put_unaligned_be32(*reg, buf + SPI_TRANS_PREFIX_LEN);
> +	memset(buf + SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH, 0xff,
> +	       SPI_READ_DUMMY_LEN);
> +
> +	xfers.tx_buf = buf;
> +	xfers.rx_buf = buf;
> +	xfers.len = SPI_READ_PREFIX_LEN + val_size;
> +	xfers.cs_change = 0;
> +	spi_message_add_tail(&xfers, &spi_msg);
> +
> +	ret = spi_sync(spi, &spi_msg);
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "transfer error:%d", ret);
> +		goto exit;
> +	}

My comment is purely idiomatic, but this seems cleaner:

	ret = ...
	if (ret)
		dev_err(...);
	else
		memcpy(...);

	kfree(...);
	return ret;

> +
> +	memcpy(val_buf, buf + SPI_READ_PREFIX_LEN, val_size);
> +exit:
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static int goodix_berlin_spi_write(void *context, const void *data,
> +				   size_t count)
> +{
> +	unsigned int len = count - REGISTER_WIDTH;
> +	struct spi_device *spi = context;
> +	struct spi_transfer xfers;
> +	struct spi_message spi_msg;
> +	const u32 *reg = data; /* reg is stored as native u32 at start of buffer */
> +	u8 *buf = NULL;
> +	int ret = 0;

Same comment here with regard to initialization.

> +
> +	buf = kzalloc(SPI_WRITE_PREFIX_LEN + len, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	spi_message_init(&spi_msg);
> +	memset(&xfers, 0, sizeof(xfers));
> +
> +	buf[0] = SPI_WRITE_FLAG;
> +	put_unaligned_be32(*reg, buf + SPI_TRANS_PREFIX_LEN);
> +	memcpy(buf + SPI_WRITE_PREFIX_LEN, data + REGISTER_WIDTH, len);
> +
> +	xfers.tx_buf = buf;
> +	xfers.len = SPI_WRITE_PREFIX_LEN + len;
> +	xfers.cs_change = 0;
> +	spi_message_add_tail(&xfers, &spi_msg);
> +
> +	ret = spi_sync(spi, &spi_msg);
> +	if (ret < 0)
> +		dev_err(&spi->dev, "transfer error:%d", ret);
> +
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static const struct regmap_config goodix_berlin_spi_regmap_conf = {
> +	.reg_bits = 32,
> +	.val_bits = 8,
> +	.read = goodix_berlin_spi_read,
> +	.write = goodix_berlin_spi_write,
> +};
> +
> +static const struct input_id goodix_berlin_spi_input_id = {
> +	.bustype = BUS_SPI,
> +	.vendor = 0x0416,
> +	.product = 0x1001,

After having seen these in the I2C counterpart; consider defining them
in goodix_berlin.h.

> +};
> +
> +static int goodix_berlin_spi_probe(struct spi_device *spi)
> +{
> +	struct regmap_config *cfg;

regmap_config

> +	struct regmap *map;

regmap

(see more examples in MFD where such dual-mode devices are common).

> +	size_t max_size;
> +	int ret = 0;
> +
> +	cfg = devm_kmemdup(&spi->dev, &goodix_berlin_spi_regmap_conf,
> +			   sizeof(*cfg), GFP_KERNEL);
> +	if (!cfg)
> +		return -ENOMEM;
> +
> +	spi->mode = SPI_MODE_0;
> +	spi->bits_per_word = 8;
> +	ret = spi_setup(spi);
> +	if (ret)
> +		return ret;
> +
> +	max_size = spi_max_transfer_size(spi);
> +	cfg->max_raw_read = max_size - SPI_READ_PREFIX_LEN;
> +	cfg->max_raw_write = max_size - SPI_WRITE_PREFIX_LEN;
> +
> +	map = devm_regmap_init(&spi->dev, NULL, spi, cfg);
> +	if (IS_ERR(map))
> +		return PTR_ERR(map);
> +
> +	return goodix_berlin_probe(&spi->dev, spi->irq,
> +				   &goodix_berlin_spi_input_id, map);
> +}
> +
> +static void goodix_berlin_spi_remove(struct spi_device *spi)
> +{
> +	goodix_berlin_remove(&spi->dev);
> +}
> +
> +static const struct of_device_id goodix_berlin_spi_of_match[] = {
> +	{
> +		.compatible = "goodix,gt9916",
> +	},

This format is different than its I2C counterpart.

> +	{ },

Nit: same comment with regards to trailing commas.

> +};
> +MODULE_DEVICE_TABLE(of, goodix_berlin_spi_of_match);
> +
> +static const struct spi_device_id goodix_berlin_spi_ids[] = {
> +	{ "gt9916" },
> +	{ },

And here.

> +};
> +MODULE_DEVICE_TABLE(spi, goodix_berlin_spi_ids);
> +
> +static struct spi_driver goodix_berlin_spi_driver = {
> +	.driver = {
> +		.name = "goodix-berlin-spi",
> +		.of_match_table = goodix_berlin_spi_of_match,
> +		.pm = pm_sleep_ptr(&goodix_berlin_pm_ops),
> +	},
> +	.id_table = goodix_berlin_spi_ids,
> +	.probe = goodix_berlin_spi_probe,
> +	.remove = goodix_berlin_spi_remove,
> +};
> +module_spi_driver(goodix_berlin_spi_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Goodix Berlin SPI Touchscreen driver");
> +MODULE_AUTHOR("Neil Armstrong <neil.armstrong@...aro.org>");
> 
> -- 
> 2.34.1
> 

Kind regards,
Jeff LaBundy

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