Date:   Mon, 22 Nov 2021 12:07:52 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Michal Simek <michal.simek@xilinx.com>
Cc:     Piyush Mehta <piyush.mehta@xilinx.com>, robh+dt@kernel.org,
        mka@chromium.org, ravisadineni@chromium.org,
        stern@rowland.harvard.edu, alcooperx@gmail.com,
        linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, git@xilinx.com, sgoud@xilinx.com
Subject: Re: [PATCH V2 2/2] usb: misc: usb244: add support for USB2 ultra
 fast sd controller
Message-ID: <YZt6CMY3IYRJkmcJ@kroah.com>
References: <20211122062834.1812005-1-piyush.mehta@xilinx.com>
 <20211122062834.1812005-3-piyush.mehta@xilinx.com>
 <YZtAb9lz8WLnWu7E@kroah.com>
 <b4064914-40b5-3789-bebd-793cb27a29cd@xilinx.com>
MIME-Version: 1.0
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In-Reply-To: <b4064914-40b5-3789-bebd-793cb27a29cd@xilinx.com>
Precedence: bulk

On Mon, Nov 22, 2021 at 12:02:52PM +0100, Michal Simek wrote:
> 
> nit: Just spot typo in subject. It is usb2244.
> 
> On 11/22/21 08:02, Greg KH wrote:
> > On Mon, Nov 22, 2021 at 11:58:34AM +0530, Piyush Mehta wrote:
> > > Microchip's USB224x family of Hi-Speed USB 2.0 flash media card controllers
> > > provides an ultra-fast interface between a USB host controller and flash
> > > media cards.
> > > 
> > > This patch adds a GPIO based usb-sd reset for USB2244 USB2 ultra fast
> > > SD controller. This usb2244 driver trigger sd reset signal after soft
> > > reset or core Reset. The SD needs to be resetted after completion of
> > > phy initialization. After the toggling of gpio, controller gets out
> > > form reset. USB2244 is a simple platform device driver.
> > > 
> > > As part of the reset, sets the direction of the pin to output before
> > > toggling the pin. Delay of microseconds is added in between high and
> > > low to meet the setup and hold time requirement of the reset.
> > > 
> > > Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
> > > ---
> > > Changes for V2:
> > > - Update reset polarity, make reset ACTIVE LOW in the usb2244 driver.
> > > - Fix WARNING: msleep < 20ms can sleep for up to 20ms by changing msleep to
> > >    usleep_range()
> > > ---
> > >   drivers/usb/misc/Kconfig   | 10 +++++++
> > >   drivers/usb/misc/Makefile  |  1 +
> > >   drivers/usb/misc/usb2244.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++
> > 
> > This isn't really a USB driver, so maybe drivers/misc/ instead?
> > 
> > >   3 files changed, 80 insertions(+)
> > >   create mode 100644 drivers/usb/misc/usb2244.c
> > > 
> > > diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> > > index 8f11443..e1c66a2 100644
> > > --- a/drivers/usb/misc/Kconfig
> > > +++ b/drivers/usb/misc/Kconfig
> > > @@ -215,6 +215,16 @@ config USB_ISIGHTFW
> > >   	  driver beforehand. Tools for doing so are available at
> > >   	  http://bersace03.free.fr
> > > +config USB_USB2244
> > > +	tristate "Microchip USB2244 Ultra Fast USB 2.0 SD driver"
> > > +	depends on GPIOLIB
> > > +	help
> > > +	  Say Y or M here if you want to reset Microchip USB2244 Ultra Fast
> > > +	  USB 2.0 SD controller.
> > > +	  This option enables support for Microchip USB2244 Ultra Fast USB 2.0
> > > +	  SD controller. This driver reset the gpio pin makes controller out of
> > > +	  reset.
> > 
> > Module name?
> > 
> > > +
> > >   config USB_YUREX
> > >   	tristate "USB YUREX driver support"
> > >   	help
> > > diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
> > > index 5f4e598..5b4af7d 100644
> > > --- a/drivers/usb/misc/Makefile
> > > +++ b/drivers/usb/misc/Makefile
> > > @@ -21,6 +21,7 @@ obj-$(CONFIG_USB_LEGOTOWER)		+= legousbtower.o
> > >   obj-$(CONFIG_USB_TEST)			+= usbtest.o
> > >   obj-$(CONFIG_USB_EHSET_TEST_FIXTURE)    += ehset.o
> > >   obj-$(CONFIG_USB_TRANCEVIBRATOR)	+= trancevibrator.o
> > > +obj-$(CONFIG_USB_USB2244)		+= usb2244.o
> > >   obj-$(CONFIG_USB_USS720)		+= uss720.o
> > >   obj-$(CONFIG_USB_SEVSEG)		+= usbsevseg.o
> > >   obj-$(CONFIG_USB_YUREX)			+= yurex.o
> > > diff --git a/drivers/usb/misc/usb2244.c b/drivers/usb/misc/usb2244.c
> > > new file mode 100644
> > > index 0000000..5a868c2
> > > --- /dev/null
> > > +++ b/drivers/usb/misc/usb2244.c
> > > @@ -0,0 +1,69 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Driver for the Microchip USB2244 Ultra Fast USB 2.0 Multi-Format,
> > > + * SD/MMC, and MS Flash Media Controllers
> > > + *
> > > + * Copyright (c) 2021 Xilinx, Inc.
> > > + */
> > > +
> > > +#include <linux/delay.h>
> > > +#include <linux/err.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/module.h>
> > > +#include <linux/of_platform.h>
> > > +#include <linux/gpio/consumer.h>
> > > +#include <linux/platform_device.h>
> > > +
> > > +struct usb2244 {
> > > +	struct gpio_desc *reset_gpio;
> > > +};
> > 
> > Why is this structure needed?
> > 
> > > +
> > > +static int usb2244_init_hw(struct device *dev, struct usb2244 *data)
> > > +{
> > > +	data = devm_kzalloc(dev, sizeof(struct usb2244), GFP_KERNEL);
> > > +	if (!data)
> > > +		return -ENOMEM;
> > > +
> > > +	data->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> > > +	if (IS_ERR(data->reset_gpio)) {
> > > +		dev_err_probe(dev, PTR_ERR(data->reset_gpio),
> > > +			      "Failed to request reset GPIO %ld, errcode",
> > > +			      PTR_ERR(data->reset_gpio));
> > > +		return PTR_ERR(data->reset_gpio);
> > > +	}
> > > +
> > > +	/* Toggle RESET_N to reset the hub. */
> > > +	gpiod_set_value_cansleep(data->reset_gpio, 1);
> > > +	usleep_range(5, 10);
> > > +	gpiod_set_value_cansleep(data->reset_gpio, 0);
> > > +	usleep_range(5000, 6000);
> > 
> > Why do you need a kernel driver for this at all?  Why not just toggle
> > the pin from userspace?
> 
> It is usb-sd convertor. If you have rootfs on SD you need to get the chip
> out of reset to be able to access init. There is no way how to do it via
> userspace.

Ah, ok, that makes more sense.

So it belongs in drivers/misc/ along with the other "enable some USB
hardware" platform drivers that we have in there today.

thanks,

greg k-h