From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Oliver Neukum <oneukum@suse.com>, Ye Xiang <xiang.ye@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
Matthias Kaehlcke <mka@chromium.org>, Lee Jones <lee@kernel.org>,
Wolfram Sang <wsa@kernel.org>, Tyrone Ting <kfting@nuvoton.com>,
Mark Brown <broonie@kernel.org>,
Bartosz Golaszewski <brgl@bgdev.pl>,
linux-usb@vger.kernel.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
linux-gpio@vger.kernel.org, srinivas.pandruvada@intel.com,
heikki.krogerus@linux.intel.com, sakari.ailus@linux.intel.com,
zhifeng.wang@intel.com, wentong.wu@intel.com,
lixu.zhang@intel.com
Subject: Re: [PATCH v4 2/5] gpio: Add support for Intel LJCA USB GPIO driver
Date: Thu, 9 Mar 2023 15:36:44 +0100 [thread overview]
Message-ID: <ZAnu/GlpS32BgmqG@kroah.com> (raw)
In-Reply-To: <CACRpkdYQfT=JXvmjKR_9O74H2dmwx1EF4QjCHM6fKAetpbrMOg@mail.gmail.com>
On Thu, Mar 09, 2023 at 03:18:53PM +0100, Linus Walleij wrote:
> On Thu, Mar 9, 2023 at 2:53 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Thu, Mar 09, 2023 at 02:40:10PM +0100, Oliver Neukum wrote:
> > > On 09.03.23 08:10, Ye Xiang wrote:
> > >
> > > > +#define LJCA_GPIO_BUF_SIZE 60
> > > > +struct ljca_gpio_dev {
> > > > + struct platform_device *pdev;
> > > > + struct gpio_chip gc;
> > > > + struct ljca_gpio_info *gpio_info;
> > > > + DECLARE_BITMAP(unmasked_irqs, LJCA_MAX_GPIO_NUM);
> > > > + DECLARE_BITMAP(enabled_irqs, LJCA_MAX_GPIO_NUM);
> > > > + DECLARE_BITMAP(reenable_irqs, LJCA_MAX_GPIO_NUM);
> > > > + u8 *connect_mode;
> > > > + /* mutex to protect irq bus */
> > > > + struct mutex irq_lock;
> > > > + struct work_struct work;
> > > > + /* lock to protect package transfer to Hardware */
> > > > + struct mutex trans_lock;
> > > > +
> > > > + u8 obuf[LJCA_GPIO_BUF_SIZE];
> > > > + u8 ibuf[LJCA_GPIO_BUF_SIZE];
> > >
> > > And here we have a violation of DMA coherency rules.
> > > Basically you cannot embed buffers into other data structures
> > > if they can be subject to DMA.
> >
> > Huh?!
> >
> > The problem here is alignment. But other than that I can't see the issue with
> > embedding into structures the instances of which will be allocated on the heap.
>
> Yups. And I think the solution looks something like this:
>
> u8 obuf[LJCA_GPIO_BUF_SIZE] __aligned(8);
> u8 ibuf[LJCA_GPIO_BUF_SIZE] __aligned(8);
>
> __aligned(4) if it's 32bit DMA I guess? 8 always works that's
> why we use it all over the IIO subsystem.
To make it all simple, just make obuf and ibuf pointers to the data you
allocate with a call to kmalloc().
thanks,
greg k-h
next prev parent reply other threads:[~2023-03-09 14:37 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-09 7:10 [PATCH v4 0/5] Add Intel LJCA device driver Ye Xiang
2023-03-09 7:10 ` [PATCH v4 1/5] mfd: Add support for Intel LJCA device Ye Xiang
2023-03-09 7:49 ` Greg Kroah-Hartman
2023-03-09 9:10 ` Ye, Xiang
2023-03-09 9:26 ` Greg Kroah-Hartman
2023-03-09 10:16 ` Ye, Xiang
2023-03-09 7:52 ` Greg Kroah-Hartman
2023-03-09 9:31 ` Ye, Xiang
2023-03-09 9:41 ` Greg Kroah-Hartman
2023-03-09 10:06 ` Andi Shyti
2023-03-09 15:45 ` Ye, Xiang
2023-03-09 15:58 ` Greg Kroah-Hartman
2023-03-09 17:42 ` Ye, Xiang
2023-03-09 7:56 ` Arnd Bergmann
2023-03-09 10:00 ` Ye, Xiang
2023-03-09 11:03 ` Mark Brown
2023-03-09 11:30 ` Arnd Bergmann
2023-03-09 12:53 ` Oliver Neukum
2023-03-10 4:14 ` Ye, Xiang
2023-03-13 13:27 ` Oliver Neukum
2023-03-14 7:15 ` Ye, Xiang
2023-03-09 7:10 ` [PATCH v4 2/5] gpio: Add support for Intel LJCA USB GPIO driver Ye Xiang
2023-03-09 13:40 ` Oliver Neukum
2023-03-09 13:52 ` Andy Shevchenko
2023-03-09 14:06 ` Greg Kroah-Hartman
2023-03-09 14:18 ` Linus Walleij
2023-03-09 14:36 ` Greg Kroah-Hartman [this message]
2023-03-09 14:48 ` Arnd Bergmann
2023-03-09 17:37 ` Oliver Neukum
2023-03-09 17:30 ` Oliver Neukum
2023-03-10 5:01 ` Ye, Xiang
2023-03-10 7:11 ` Greg Kroah-Hartman
2023-03-10 7:39 ` Ye, Xiang
2023-03-10 7:53 ` Greg Kroah-Hartman
2023-03-10 8:59 ` Ye, Xiang
2023-03-11 12:13 ` Krzysztof Kozlowski
2023-03-12 15:40 ` Ye, Xiang
2023-03-09 7:10 ` [PATCH v4 3/5] i2c: Add support for Intel LJCA USB I2C driver Ye Xiang
2023-03-09 7:10 ` [PATCH v4 4/5] spi: Add support for Intel LJCA USB SPI driver Ye Xiang
2023-03-09 7:11 ` [PATCH v4 5/5] Documentation: Add ABI doc for attributes of LJCA device Ye Xiang
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