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Date: Tue, 27 Nov 2018 01:21:27 +0100
From: Anatolij Gustschin <agust@...x.de>
To: Mark Brown <broonie@...nel.org>
Cc: linux-usb@...r.kernel.org, linux-spi@...r.kernel.org,
linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org, atull@...nel.org, mdf@...nel.org
Subject: Re: [PATCH v2 2/3] spi: add FTDI MPSSE SPI controller driver
On Wed, 21 Nov 2018 12:42:37 +0000
Mark Brown broonie@...nel.org wrote:
...
>> obj-$(CONFIG_SPI_ZYNQMP_GQSPI) += spi-zynqmp-gqspi.o
>> +obj-$(CONFIG_SPI_FTDI_MPSSE) += spi-ftdi-mpsse.o
>>
>> # SPI slave protocol handlers
>> obj-$(CONFIG_SPI_SLAVE_TIME) += spi-slave-time.o
>
>Please keep the Makefile sorted.
Will fix it in v3.
>> +++ b/drivers/spi/spi-ftdi-mpsse.c
>> @@ -0,0 +1,673 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * FTDI FT232H MPSSE SPI controller driver
>
>Please make the entire comment block here a C++ one so it looks more
>consistent.
Okay.
>> + struct gpiod_lookup_table *lookup[13];
>
>This magic number for the size of the lookup table is not good.
Will fix it in v3.
>> +static void ftdi_spi_chipselect(struct ftdi_spi *priv, struct spi_device *spi,
>> + bool value)
>> +{
>> + int cs = spi->chip_select;
>> +
>> + dev_dbg(&priv->master->dev, "%s: CS %d, cs mode %d, val %d\n",
>> + __func__, cs, (spi->mode & SPI_CS_HIGH), value);
>> +
>> + gpiod_set_raw_value_cansleep(priv->cs_gpios[cs], value);
>> +}
>
>This is just a gpio chip select - can't it be handled by the core chip
>select code?
spi core chip select code doesn't use gpio_desc based API yet.
But it can be handled using .set_cs(), I'll convert the driver
to use .set_cs().
>> + remaining = len;
>> + do {
>> + stride = min_t(size_t, remaining, SZ_64K - 3);
>
>Rather than having a magic number for the buffer size it would be better
>to either have a driver specific constant that's used consistently or
>just use sizeof() when it's referenced in the code. That way if the
>buffer size is changed nothing will get missed.
sizeof() is better choice here, will use it in v3.
>> + /* Last transfer with cs_change set, stop keeping CS */
>> + if (list_is_last(&t->transfer_list, &msg->transfers)) {
>> + keep_cs = true;
>> + break;
>> + }
>> + ftdi_spi_chipselect(priv, spi, !(spi->mode & SPI_CS_HIGH));
>> + usleep_range(10, 15);
>> + ftdi_spi_chipselect(priv, spi, spi->mode & SPI_CS_HIGH);
>
>I'm not clear what this is intended to do? It's overall not clear to me
>that the driver needs to use transfer_one_message and not transfer_one,
>the latter keeps more of the code in common code.
It has been a while since I started with this driver, I don't remember
the intention of this chip select toggling here. I'll convert the
driver to use .transfer_one().
>> + /* Find max. slave chipselect number */
>> + num_cs = pd->spi_info_len;
>> + for (i = 0; i < num_cs; i++) {
>> + if (max_cs < pd->spi_info[i].chip_select)
>> + max_cs = pd->spi_info[i].chip_select;
>> + }
>> +
>> + if (max_cs > 12) {
>> + dev_err(dev, "Invalid max CS in platform data: %d\n", max_cs);
>> + return -EINVAL;
>> + }
>> + dev_dbg(dev, "CS count %d, max CS %d\n", num_cs, max_cs);
>> + max_cs += 1; /* including CS0 */
>
>Why not just size the array based on the platform data?
The driver must also support multiple SPI slaves with additional control
pins (besides SPI chip-select gpios). There are devices with not adjacent
chip-select gpios or devices with single chip-select gpio starting at
some offset. The array size is not always the number of chip-selects
or the max. chip-select, e.g.:
$ tree /sys/bus/spi/devices/
/sys/bus/spi/devices/
├── spi0.4 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.4/2-1.2.4:1.0/ftdi-mpsse-spi.0/spi_master/spi0/spi0.4
├── spi1.0 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.3/2-1.2.3:1.0/ftdi-mpsse-spi.1/spi_master/spi1/spi1.0
├── spi1.12 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.3/2-1.2.3:1.0/ftdi-mpsse-spi.1/spi_master/spi1/spi1.12
├── spi1.4 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.3/2-1.2.3:1.0/ftdi-mpsse-spi.1/spi_master/spi1/spi1.4
└── spi1.8 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.3/2-1.2.3:1.0/ftdi-mpsse-spi.1/spi_master/spi1/spi1.8
$ sudo cat /sys/kernel/debug/gpio
gpiochip1: GPIOs 486-498, parent: usb/2-1.2.3:1.0, ftdi-mpsse-gpio.1, can sleep:
gpio-486 (mpsse.1-CS |spi-cs ) out hi ACTIVE LOW
gpio-487 (mpsse.1-GPIOL0 |confd ) in hi
gpio-488 (mpsse.1-GPIOL1 |nstat ) in hi ACTIVE LOW
gpio-489 (mpsse.1-GPIOL2 |nconfig ) out hi ACTIVE LOW
gpio-490 (mpsse.1-GPIOL3 |spi-cs ) out hi ACTIVE LOW
gpio-491 (mpsse.1-GPIOH0 |confd ) in hi
gpio-492 (mpsse.1-GPIOH1 |nstat ) in hi ACTIVE LOW
gpio-493 (mpsse.1-GPIOH2 |nconfig ) out hi ACTIVE LOW
gpio-494 (mpsse.1-GPIOH3 |spi-cs ) out hi ACTIVE LOW
gpio-495 (mpsse.1-GPIOH4 |confd ) in hi
gpio-496 (mpsse.1-GPIOH5 |nstat ) in hi ACTIVE LOW
gpio-497 (mpsse.1-GPIOH6 |nconfig ) out hi ACTIVE LOW
gpio-498 (mpsse.1-GPIOH7 |spi-cs ) out hi
gpiochip0: GPIOs 499-511, parent: usb/2-1.2.4:1.0, ftdi-mpsse-gpio.0, can sleep:
gpio-499 (mpsse.0-CS )
gpio-500 (mpsse.0-GPIOL0 )
gpio-501 (mpsse.0-GPIOL1 )
gpio-502 (mpsse.0-GPIOL2 )
gpio-503 (mpsse.0-GPIOL3 |spi-cs ) out hi ACTIVE LOW
gpio-504 (mpsse.0-GPIOH0 |confd ) in hi
gpio-505 (mpsse.0-GPIOH1 |nstat ) in hi ACTIVE LOW
gpio-506 (mpsse.0-GPIOH2 |nconfig ) out hi ACTIVE LOW
gpio-507 (mpsse.0-GPIOH3 )
gpio-508 (mpsse.0-GPIOH4 )
gpio-509 (mpsse.0-GPIOH5 )
gpio-510 (mpsse.0-GPIOH6 )
gpio-511 (mpsse.0-GPIOH7 )
Thanks,
Anatolij
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