Re: [PATCH v1 2/2] spi: loongson: add bus driver for the loongson spi controller

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


在 2023/3/8 下午11:03, Mark Brown 写道:
On Wed, Mar 08, 2023 at 10:59:08AM +0800, Yinbo Zhu wrote:

+	tristate "Loongson SPI Controller Support"
+	depends on LOONGARCH && OF && PCI
I'm not seeing any build time dependencies here (possibly PCI?) so
please add an || COMPILE_TEST to improve build coverage.  It'd be better
to have separate modules for the platform and PCI functionality, that
way someone who has a system without PCI can still use the driver even
with PCI support disabled.

I will add an || COMPILE_TEST and drop && PCI then add some CONFIG_PCI macro

to limit some pci code.

+++ b/drivers/spi/spi-loongson.c
@@ -0,0 +1,502 @@
+// SPDX-License-Identifier: GPL-2.0+
+ * Loongson SPI Support
+ *
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
Please make the entire comment block a C++ one so things look more
okay, I got it.

+static int loongson_spi_update_state(struct loongson_spi *loongson_spi,
+				     struct spi_device *spi, struct spi_transfer *t)
+	unsigned int hz;
+	unsigned int div, div_tmp;
+	unsigned int bit;
+	unsigned char val;
+	const char rdiv[12] = {0, 1, 4, 2, 3, 5, 6, 7, 8, 9, 10, 11};
+	hz  = t ? t->speed_hz : spi->max_speed_hz;
Please write normal conditional statements so that things are legible,
though in this case the core will ensure that there's a speed_hz in
every transfer so there's no need for any of the logic around ensuring
it's set.
Do you mean to achieve the following ?  and drop spi->max_speed_hz.

if (t)

      hz = t->speed_hz;

+static int loongson_spi_setup(struct spi_device *spi)
+	struct loongson_spi *loongson_spi;
+	loongson_spi = spi_master_get_devdata(spi->master);
+	if (spi->bits_per_word % 8)
+		return -EINVAL;
+	if (spi->chip_select >= spi->master->num_chipselect)
+		return -EINVAL;
+	loongson_spi_update_state(loongson_spi, spi, NULL);
+	loongson_spi_set_cs(loongson_spi, spi, 1);
Note that setup() needs to be able to run for one device while there are
transfers for other devices on the same controller active.
okay, I will add a spin_lock for it.

+static int loongson_spi_write_read_8bit(struct spi_device *spi, const u8 **tx_buf,
+					u8 **rx_buf, unsigned int num)
+	struct loongson_spi *loongson_spi = spi_master_get_devdata(spi->master);
+	if (tx_buf && *tx_buf) {
+		loongson_spi_write_reg(loongson_spi, LOONGSON_SPI_FIFO_REG, *((*tx_buf)++));
+		while ((loongson_spi_read_reg(loongson_spi, LOONGSON_SPI_SPSR_REG) & 0x1) == 1)
+			;
A timeout would be good on these spins in case the controller gets
stuck.  It'd also be polite to have a cpu_relax() somewhere either here
or in the caller given that it's busy waiting.
okay, I got it.

+static void loongson_spi_work(struct work_struct *work)
+	int param;
+	struct spi_message *m;
+	struct spi_device  *spi;
+	struct spi_transfer *t = NULL;
+	struct loongson_spi *loongson_spi = container_of(work, struct loongson_spi, work);
+	spin_lock(&loongson_spi->lock);
+	param = loongson_spi_read_reg(loongson_spi, LOONGSON_SPI_PARA_REG);
+	loongson_spi_write_reg(loongson_spi, LOONGSON_SPI_PARA_REG, param&~1);
+	while (!list_empty(&loongson_spi->msg_queue)) {
+		m = container_of(loongson_spi->, struct spi_message, queue);
This all looks like it's open coding the core's message pump, only
without the heavy optimisation work that the core has and missing some
handling of cs_change and delays.  You should implement
spi_transfer_one() instead, this will save a lot of code and should be
more performant.
okay, I will try to add a spi_transfer_one for this.

+static int loongson_spi_transfer(struct spi_device *spi, struct spi_message *m)
In general you'd need an extremely strong reason to implement transfer()
in a new driver.
okay, I got it.

+static int __maybe_unused loongson_spi_resume(struct device *dev)
+static const struct dev_pm_ops loongson_spi_dev_pm_ops = {
+	.suspend = loongson_spi_suspend,
+	.resume = loongson_spi_resume,
The suspend/resume ops are assigned unconditionally.
sorry, I don't got it,  you mean was to  add a CONFIG_PM to limit code ?

Why not just a regular module initcall like most SPI drivers?
okay, I will use module_init for register spi drivers.

[Index of Archives]     [Linux Kernel]     [Linux ARM (vger)]     [Linux ARM MSM]     [Linux Omap]     [Linux Arm]     [Linux Tegra]     [Fedora ARM]     [Linux for Samsung SOC]     [eCos]     [Linux Fastboot]     [Gcc Help]     [Git]     [DCCP]     [IETF Announce]     [Security]     [Linux MIPS]     [Yosemite Campsites]

  Powered by Linux