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SubjectRe: [PATCH v4 2/3] clocksource: Rewrite Xilinx AXI timer driver
On Fri, 28 May 2021, Sean Anderson wrote:

> This rewrites the Xilinx AXI timer driver to be more platform agnostic.
> Some common code has been split off so it can be reused. These routines
> currently live in drivers/mfd. The largest changes have taken place in the
> initialization:
>
> - We now support any number of timer devices, possibly with only one
> counter each. The first counter will be used as a clocksource. Every
> other counter will be used as a clockevent.
> - We do not use timer_of_init because we need to perform some tasks in
> between different stages. For example, we must ensure that ->read and
> ->write are initialized before registering the irq. This can only happen
> after we have gotten the register base (to detect endianness). We also
> have a rather unusual clock initialization sequence in order to remain
> backwards compatible. Due to this, it's ok for the initial clock request
> to fail, and we do not want other initialization to be undone. Lastly, it
> is more convenient to do one allocation for xilinx_clockevent_device than
> to do one for timer_of and one for xilinx_timer_priv.
> - We now pay attention to xlnx,count-width and handle smaller width timers.
> The default remains 32.
>
> Signed-off-by: Sean Anderson <sean.anderson@seco.com>
> ---
> This has been tested on microblaze qemu.
>
> Changes in v4:
> - Break out clock* drivers into their own file
>
> arch/microblaze/kernel/Makefile | 3 +-
> arch/microblaze/kernel/timer.c | 326 -----------------------------
> drivers/clocksource/Kconfig | 11 +
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-xilinx.c | 300 ++++++++++++++++++++++++++
> drivers/mfd/Makefile | 4 +
> drivers/mfd/xilinx-timer.c | 147 +++++++++++++

I'm confused!

> include/linux/mfd/xilinx-timer.h | 134 ++++++++++++
> 8 files changed, 598 insertions(+), 328 deletions(-)
> delete mode 100644 arch/microblaze/kernel/timer.c
> create mode 100644 drivers/clocksource/timer-xilinx.c
> create mode 100644 drivers/mfd/xilinx-timer.c
> create mode 100644 include/linux/mfd/xilinx-timer.h

[...]

> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com>
> + *
> + * For Xilinx LogiCORE IP AXI Timer documentation, refer to DS764:
> + * https://www.xilinx.com/support/documentation/ip_documentation/axi_timer/v1_03_a/axi_timer_ds764.pdf
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/mfd/xilinx-timer.h>
> +#include <linux/of.h>
> +#include <asm/io.h>

RED FLAG: You are not using the MFD API here.

> +#define TCSR0 0x00
> +#define TLR0 0x04
> +#define TCR0 0x08
> +#define TCSR1 0x10
> +#define TLR1 0x14
> +#define TCR1 0x18
> +
> +#define TCSR_MDT BIT(0)
> +#define TCSR_UDT BIT(1)
> +#define TCSR_GENT BIT(2)
> +#define TCSR_CAPT BIT(3)
> +#define TCSR_ARHT BIT(4)
> +#define TCSR_LOAD BIT(5)
> +#define TCSR_ENIT BIT(6)
> +#define TCSR_ENT BIT(7)
> +#define TCSR_TINT BIT(8)
> +#define TCSR_PWMA BIT(9)
> +#define TCSR_ENALL BIT(10)
> +#define TCSR_CASC BIT(11)
> +
> +/* readl/writel wrappers to support BE systems */
> +
> +static u32 xilinx_ioread32be(const void __iomem *addr)
> +{
> + return ioread32be(addr);
> +}
> +
> +static void xilinx_iowrite32be(u32 value, void __iomem *addr)
> +{
> + iowrite32be(value, addr);
> +}
> +
> +static u32 xilinx_ioread32(const void __iomem *addr)
> +{
> + return ioread32(addr);
> +}
> +
> +static void xilinx_iowrite32(u32 value, void __iomem *addr)
> +{
> + iowrite32(value, addr);
> +}

Abstraction for the sake of abstraction, is not allowed.

Just use the io*() calls directly in-place.

> +int xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 *tlr,
> + u32 tcsr, u64 cycles)
> +{
> + if (cycles < 2 || cycles > priv->max + 2)
> + return -ERANGE;
> +
> + if (tcsr & TCSR_UDT)
> + *tlr = cycles - 2;
> + else
> + *tlr = priv->max - cycles + 2;
> +
> + return 0;
> +}
> +
> +int xilinx_timer_tlr_period(struct xilinx_timer_priv *priv, u32 *tlr,
> + u32 tcsr, unsigned int period)
> +{
> + u64 cycles = DIV_ROUND_DOWN_ULL((u64)period * clk_get_rate(priv->clk),
> + NSEC_PER_SEC);
> +
> + return xilinx_timer_tlr_cycles(priv, tlr, tcsr, cycles);
> +}
> +
> +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv,
> + u32 tlr, u32 tcsr)
> +{
> + u64 cycles;
> +
> + if (tcsr & TCSR_UDT)
> + cycles = tlr + 2;
> + else
> + cycles = priv->max - tlr + 2;
> +
> + return DIV_ROUND_UP_ULL(cycles * NSEC_PER_SEC,
> + clk_get_rate(priv->clk));
> +}
> +
> +int xilinx_timer_common_init(struct device_node *np,
> + struct xilinx_timer_priv *priv,
> + u32 *one_timer)
> +{
> + int ret;
> + u32 tcsr0, width;
> +
> +
> + priv->read = xilinx_ioread32;
> + priv->write = xilinx_iowrite32;
> + /*
> + * If PWM mode is enabled, we should try not to disturb it. Use
> + * CAPT since if PWM mode is enabled then MDT will be set as
> + * well.
> + *
> + * First, clear CAPT and verify that it has been cleared
> + */
> + tcsr0 = xilinx_timer_read(priv, TCSR0);
> + xilinx_timer_write(priv, tcsr0 & ~(TCSR_CAPT & swab(TCSR_CAPT)), TCSR0);
> + tcsr0 = xilinx_timer_read(priv, TCSR0);
> + if (tcsr0 & (TCSR_CAPT | swab(TCSR_CAPT))) {
> + pr_err("%pOF: cannot determine endianness\n", np);
> + return -EOPNOTSUPP;
> + }
> +
> + /* Then check to make sure our write sticks */
> + xilinx_timer_write(priv, tcsr0 | TCSR_CAPT, TCSR0);
> + if (!(xilinx_timer_read(priv, TCSR0) & TCSR_CAPT)) {
> + priv->read = xilinx_ioread32be;
> + priv->write = xilinx_iowrite32be;
> + }
> +
> + ret = of_property_read_u32(np, "xlnx,one-timer-only", one_timer);
> + if (ret) {
> + pr_err("%pOF: err %d: xlnx,one-timer-only\n", np, ret);
> + return ret;
> + } else if (*one_timer && *one_timer != 1) {
> + pr_err("%pOF: xlnx,one-timer-only must be 0 or 1\n", np);
> + return -EINVAL;
> + }
> +
> + ret = of_property_read_u32(np, "xlnx,count-width", &width);
> + if (ret == -EINVAL) {
> + width = 32;
> + } else if (ret) {
> + pr_err("%pOF: err %d: xlnx,count-width\n", np, ret);
> + return ret;
> + } else if (width < 8 || width > 32) {
> + pr_err("%pOF: invalid counter width\n", np);
> + return -EINVAL;
> + }
> + priv->max = BIT_ULL(width) - 1;
> +
> + return 0;
> +}

This is *all* timer stuff.

What is your rationale for dumping this into MFD?

--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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