From: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Lior Amsalem <alior@marvell.com>,
Jason Cooper <jason@lakedaemon.net>, Andrew Lunn <andrew@lunn.ch>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
Rob Herring <rob.herring@calxeda.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
devicetree-discuss@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 02/10] pinctrl: mvebu: dove pinctrl driver
Date: Tue, 18 Jun 2013 14:01:39 +0200 [thread overview]
Message-ID: <51C04C23.4090807@gmail.com> (raw)
In-Reply-To: <20130618113606.GA26763@n2100.arm.linux.org.uk>
On 06/18/13 13:36, Russell King - ARM Linux wrote:
> On Thu, Sep 13, 2012 at 05:41:44PM +0200, Sebastian Hesselbarth wrote:
>> +#define DOVE_GLOBAL_CONFIG_1 (DOVE_SB_REGS_VIRT_BASE | 0xe802C)
>> +#define DOVE_TWSI_ENABLE_OPTION1 BIT(7)
>> +#define DOVE_GLOBAL_CONFIG_2 (DOVE_SB_REGS_VIRT_BASE | 0xe8030)
>> +#define DOVE_TWSI_ENABLE_OPTION2 BIT(20)
>> +#define DOVE_TWSI_ENABLE_OPTION3 BIT(21)
>> +#define DOVE_TWSI_OPTION3_GPIO BIT(22)
> ...
Russell,
the above absolute addresses already made me think of cleaning up dove
pinctrl a while ago. I also had in mind that below function exclusively
request ownership of global config registers.
>> +static int dove_twsi_ctrl_set(struct mvebu_mpp_ctrl *ctrl,
>> + unsigned long config)
>> +{
>> + unsigned long gcfg1 = readl(DOVE_GLOBAL_CONFIG_1);
>> + unsigned long gcfg2 = readl(DOVE_GLOBAL_CONFIG_2);
>> +
>> + gcfg1 &= ~DOVE_TWSI_ENABLE_OPTION1;
>> + gcfg2 &= ~(DOVE_TWSI_ENABLE_OPTION2 | DOVE_TWSI_ENABLE_OPTION2);
>> +
>> + switch (config) {
>> + case 1:
>> + gcfg1 |= DOVE_TWSI_ENABLE_OPTION1;
>> + break;
>> + case 2:
>> + gcfg2 |= DOVE_TWSI_ENABLE_OPTION2;
>> + break;
>> + case 3:
>> + gcfg2 |= DOVE_TWSI_ENABLE_OPTION3;
>> + break;
>> + }
>> +
>> + writel(gcfg1, DOVE_GLOBAL_CONFIG_1);
>> + writel(gcfg2, DOVE_GLOBAL_CONFIG_2);
>> +
>> + return 0;
>> +}
>
> So, I've just been thinking about the LCD clocking on the Armada 510,
> and found that there's dividers for the internal LCD clocks in the
> global config 1/2 registers. So I grepped the kernel source for
> references to these, expecting to find something in drivers/clk, but
> found the above.
We have no peripheral clock handling for Dove, yet. Just core clocks and
clock gates are implemented. And I guess they are DT only anyway.
> However, todays kernel is sometimes SMP, commonly with kernel preemption
> enabled, maybe even RT. This makes things like the above sequence a
> problem where a multifunction register is read, modified and then
> written back.
>
> Consider two threads doing this, and a preemption event happening in the
> middle of this sequence to another thread also doing a read-modify-write
> of the same register. Which one wins depends on the preemption sequence,
> but ultimately one loses out.
Yeah, sure. We have the same issue with watchdog driver messing with
timer registers. There I exported a function to _clrset TIMER_CTRL
register safely. Just went into irqchip (tip for-next).
> Any access to such registers needs careful thought, and protection in some
> manner.
>
> Maybe what we need is something like this:
>
> static DEFINE_SPINLOCK(io_lock);
> static void modifyl(u32 new, u32 mask, void __iomem *reg)
> {
> unsigned long flags;
> u32 val;
>
> spin_lock_irqsave(&io_lock, flags);
> val = readl(reg) & ~mask;
> val |= new | mask;
> writel(val, reg);
> spin_unlock_irqrestore(&io_lock, flags);
> }
>
> in order to provide arbitrated access to these kinds of multifunction
> registers in a safe, platform agnostic way.
I am fine with a generic modify function with a single lock. Most cases
should be fine with a single lock even for non-related register
accesses, e.g. watchdog will access TIMER_CTRL only once to enable
itself. If you think you need a special lock because you have a lot of
writes to shared registers, you can still have your own modify lock.
Sebastian
next prev parent reply other threads:[~2013-06-18 12:01 UTC|newest]
Thread overview: 136+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-11 12:56 [PATCH 00/11] pinctrl: mvebu: pinctrl driver Sebastian Hesselbarth
2012-08-11 12:56 ` [PATCH 01/11] pinctrl: mvebu: pinctrl driver core Sebastian Hesselbarth
2012-08-20 9:09 ` Linus Walleij
2012-08-20 9:46 ` Sebastian Hesselbarth
2012-08-20 12:51 ` Thomas Petazzoni
2012-08-20 14:18 ` Linus Walleij
2012-08-20 14:51 ` Sebastian Hesselbarth
2012-08-25 8:22 ` Andrew Lunn
2012-08-20 14:11 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 02/11] pinctrl: mvebu: dove pinctrl driver Sebastian Hesselbarth
2012-08-20 13:43 ` Linus Walleij
2012-08-20 14:43 ` Sebastian Hesselbarh
2012-08-20 17:16 ` Thomas Petazzoni
2012-08-11 12:56 ` [PATCH 03/11] pinctrl: mvebu: kirkwood " Sebastian Hesselbarth
2012-08-20 13:49 ` Linus Walleij
2012-08-27 13:43 ` Ben Dooks
2012-08-27 19:19 ` Sebastian Hesselbarth
2012-08-27 20:02 ` Stephen Warren
2012-08-11 12:56 ` [PATCH 04/11] pinctrl: mvebu: add pinctrl driver for Armada 370 Sebastian Hesselbarth
2012-08-20 14:25 ` Linus Walleij
2012-08-20 16:48 ` Sebastian Hesselbarth
2012-08-20 17:36 ` Thomas Petazzoni
2012-08-20 18:01 ` Sebastian Hesselbarth
2012-08-20 18:51 ` Thomas Petazzoni
2012-08-21 7:12 ` Gregory CLEMENT
2012-08-11 12:56 ` [PATCH 05/11] pinctrl: mvebu: add pinctrl driver for Armada XP Sebastian Hesselbarth
2012-08-20 14:26 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 06/11] ARM: mvebu: add pinctrl device in DT for Armada 370/XP SoCs Sebastian Hesselbarth
2012-08-20 14:27 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 07/11] ARM: mvebu: Add pinctrl support to Armada XP SoCs Sebastian Hesselbarth
2012-08-20 14:27 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 08/11] ARM: mvebu: Add pinctrl support to Armada 370 SoC Sebastian Hesselbarth
2012-08-20 14:28 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 09/11] ARM: mvebu: adjust Armada XP evaluation board DTS Sebastian Hesselbarth
2012-08-20 14:28 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 10/11] arm: mvebu: enable PINCTRL usage Sebastian Hesselbarth
2012-08-20 14:29 ` Linus Walleij
2012-08-11 12:56 ` [PATCH 11/11] arm: mvebu: add pinctrl support in defconfig Sebastian Hesselbarth
2012-08-20 14:31 ` Linus Walleij
2012-08-20 14:54 ` Sebastian Hesselbarth
2012-08-20 17:37 ` Thomas Petazzoni
2012-08-20 8:12 ` [PATCH 00/11] pinctrl: mvebu: pinctrl driver Linus Walleij
2012-08-22 8:22 ` [PATCH v2 0/9] " Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 1/9] pinctrl: mvebu: pinctrl driver core Sebastian Hesselbarth
2012-08-22 20:43 ` Stephen Warren
2012-08-23 9:45 ` Sebastian Hesselbarth
2012-08-23 17:54 ` Stephen Warren
2012-08-23 20:31 ` Sebastian Hesselbarth
2012-08-23 21:26 ` Stephen Warren
2012-08-23 23:01 ` Sebastian Hesselbarth
2012-08-24 3:34 ` Stephen Warren
2012-08-25 15:53 ` Sebastian Hesselbarth
2012-08-27 4:33 ` Stephen Warren
2012-09-02 7:30 ` Linus Walleij
2012-09-02 8:27 ` Sebastian Hesselbarth
2012-09-03 9:32 ` Linus Walleij
2012-09-03 19:47 ` Jason Cooper
2012-09-09 19:56 ` Jason Cooper
2012-08-22 8:22 ` [PATCH v2 2/9] pinctrl: mvebu: dove pinctrl driver Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 3/9] pinctrl: mvebu: kirkwood " Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 4/9] pinctrl: mvebu: add pinctrl driver for Armada 370 Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 5/9] pinctrl: mvebu: add pinctrl driver for Armada XP Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 6/9] ARM: mvebu: add pinctrl device in DT for Armada 370/XP SoCs Sebastian Hesselbarth
2012-08-22 8:22 ` [PATCH v2 7/9] ARM: mvebu: Add pinctrl support to Armada XP SoCs Sebastian Hesselbarth
2012-08-22 20:45 ` Stephen Warren
2012-08-22 8:22 ` [PATCH v2 8/9] ARM: mvebu: Add pinctrl support to Armada 370 SoC Sebastian Hesselbarth
2012-08-22 20:46 ` Stephen Warren
2012-08-22 8:22 ` [PATCH v2 9/9] ARM: mvebu: adjust Armada XP evaluation board DTS Sebastian Hesselbarth
2012-09-10 8:39 ` [PATCH v3 0/9] pinctrl: mvebu: pinctrl driver Sebastian Hesselbarth
2012-09-10 8:39 ` [PATCH v3 1/9] pinctrl: mvebu: pinctrl driver core Sebastian Hesselbarth
2012-09-10 15:39 ` Linus Walleij
2012-09-11 14:44 ` Thomas Petazzoni
2012-09-11 22:17 ` Stephen Warren
2012-09-12 6:04 ` Linus Walleij
2012-09-12 6:54 ` Thomas Petazzoni
2012-09-12 15:50 ` Linus Walleij
2012-09-12 16:01 ` Thomas Petazzoni
2012-09-12 16:17 ` Linus Walleij
2012-09-12 21:10 ` Stephen Warren
2012-09-10 8:39 ` [PATCH v3 2/9] pinctrl: mvebu: dove pinctrl driver Sebastian Hesselbarth
2012-09-10 15:40 ` Linus Walleij
2012-09-11 22:18 ` Stephen Warren
2012-09-10 8:39 ` [PATCH v3 3/9] pinctrl: mvebu: kirkwood " Sebastian Hesselbarth
2012-09-10 15:42 ` Linus Walleij
2012-09-10 8:39 ` [PATCH v3 4/9] pinctrl: mvebu: add pinctrl driver for Armada 370 Sebastian Hesselbarth
2012-09-10 15:43 ` Linus Walleij
2012-09-10 8:39 ` [PATCH v3 5/9] pinctrl: mvebu: add pinctrl driver for Armada XP Sebastian Hesselbarth
2012-09-10 15:43 ` Linus Walleij
2012-09-10 8:39 ` [PATCH v3 6/9] ARM: mvebu: add pinctrl device in DT for Armada 370/XP SoCs Sebastian Hesselbarth
2012-09-11 22:23 ` Stephen Warren
2012-09-12 6:56 ` Thomas Petazzoni
2012-09-12 20:57 ` Stephen Warren
2012-09-10 8:39 ` [PATCH v3 7/9] ARM: mvebu: Add pinctrl support to Armada XP SoCs Sebastian Hesselbarth
2012-09-10 8:39 ` [PATCH v3 8/9] ARM: mvebu: Add pinctrl support to Armada 370 SoC Sebastian Hesselbarth
2012-09-10 8:39 ` [PATCH v3 9/9] ARM: mvebu: adjust Armada XP evaluation board DTS Sebastian Hesselbarth
2012-09-10 15:45 ` [PATCH v3 0/9] pinctrl: mvebu: pinctrl driver Linus Walleij
2012-09-10 15:57 ` Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 00/10] " Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 01/10] pinctrl: mvebu: pinctrl driver core Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 02/10] pinctrl: mvebu: dove pinctrl driver Sebastian Hesselbarth
2013-06-18 11:36 ` Russell King - ARM Linux
2013-06-18 12:01 ` Sebastian Hesselbarth [this message]
2013-06-18 15:02 ` Linus Walleij
2013-06-18 15:11 ` Russell King - ARM Linux
2013-06-18 15:23 ` Linus Walleij
2013-06-18 18:33 ` Mark Brown
2012-09-13 15:41 ` [PATCH v4 03/10] pinctrl: mvebu: kirkwood " Sebastian Hesselbarth
2012-09-16 7:46 ` Andrew Lunn
2012-09-16 9:09 ` Sebastian Hesselbarth
2012-09-17 8:45 ` Linus Walleij
2012-09-20 15:30 ` Arnd Bergmann
2012-09-20 18:34 ` Andrew Lunn
2012-09-20 19:28 ` Linus Walleij
2012-09-20 19:36 ` Thomas Petazzoni
2012-09-20 19:51 ` Andrew Lunn
2012-09-21 10:56 ` Ben Dooks
2012-09-21 18:14 ` Linus Walleij
2012-09-16 12:40 ` Jason Cooper
2012-09-17 1:55 ` Nicolas Pitre
2012-09-17 6:36 ` Sebastian Hesselbarth
2012-09-17 8:32 ` Andrew Lunn
2012-09-18 18:59 ` Andrew Lunn
2012-09-13 15:41 ` [PATCH v4 04/10] pinctrl: mvebu: add pinctrl driver for Armada 370 Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 05/10] pinctrl: mvebu: add pinctrl driver for Armada XP Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 06/10] ARM: mvebu: Add pinctrl support to Armada XP SoCs Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 07/10] ARM: mvebu: Add pinctrl support to Armada 370 SoC Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 08/10] ARM: mvebu: adjust Armada XP evaluation board DTS Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 09/10] arm: mvebu: split Kconfig options for Armada 370 and XP Sebastian Hesselbarth
2012-09-13 15:41 ` [PATCH v4 10/10] arm: mvebu: select the pinctrl drivers for Armada 370 and Armada XP platforms Sebastian Hesselbarth
2012-09-13 15:48 ` [PATCH v4 00/10] pinctrl: mvebu: pinctrl driver Thomas Petazzoni
2012-09-14 16:41 ` Stephen Warren
2012-09-20 8:13 ` [PATCH 00/11] " Linus Walleij
2012-09-20 8:17 ` Sebastian Hesselbarth
2012-09-20 9:04 ` Thomas Petazzoni
2012-09-20 10:02 ` Andrew Lunn
2012-09-20 10:32 ` Thomas Petazzoni
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