[PATCH v2 0/2] amba/platform: Initialize dma_parms at the bus level

[PATCH v2 0/2] amba/platform: Initialize dma_parms at the bus level

[Ulf Hansson]

It's currently the amba/platform driver's responsibility to initialize the
pointer, dma_parms, for its corresponding struct device. The benefit with this
approach allows us to avoid the initialization and to not waste memory for the
struct device_dma_parameters, as this can be decided on a case by case basis.
    
However, it has turned out that this approach is not very practical. Not only
does it lead to open coding, but also to real errors. In principle callers of
dma_set_max_seg_size() doesn't check the error code, but just assumes it
succeeds.
    
For these reasons, this series initializes the dma_parms from the amba/platform
bus at the device registration point. This also follows the way the PCI devices
are being managed, see pci_device_add().

If it turns out that this is an acceptable solution, we probably also want the
changes for stable, but I am not sure if it applies without conflicts.

The series is based on v5.6.

Kind regards
Ulf Hansson


Ulf Hansson (2):
  driver core: platform: Initialize dma_parms for platform devices
  amba: Initialize dma_parms for amba devices

 drivers/amba/bus.c              | 1 +
 drivers/base/platform.c         | 2 ++
 include/linux/amba/bus.h        | 1 +
 include/linux/platform_device.h | 1 +
 4 files changed, 5 insertions(+)

-- 
2.20.1

[PATCH v2 1/2] driver core: platform: Initialize dma_parms for platform devices

[Ulf Hansson]

It's currently the platform driver's responsibility to initialize the
pointer, dma_parms, for its corresponding struct device. The benefit with
this approach allows us to avoid the initialization and to not waste memory
for the struct device_dma_parameters, as this can be decided on a case by
case basis.

However, it has turned out that this approach is not very practical.  Not
only does it lead to open coding, but also to real errors. In principle
callers of dma_set_max_seg_size() doesn't check the error code, but just
assumes it succeeds.

For these reasons, let's do the initialization from the common platform bus
at the device registration point. This also follows the way the PCI devices
are being managed, see pci_device_add().

Suggested-by: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

---

Changes in v2:
	- Move initialization to setup_pdev_dma_masks(). This means the
	initialization is done also in the OF path.

---
 drivers/base/platform.c         | 2 ++
 include/linux/platform_device.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index b5ce7b085795..c81b68d5d66d 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -361,6 +361,8 @@ struct platform_object {
  */
 static void setup_pdev_dma_masks(struct platform_device *pdev)
 {
+	pdev->dev.dma_parms = &pdev->dma_parms;
+
 	if (!pdev->dev.coherent_dma_mask)
 		pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
 	if (!pdev->dev.dma_mask) {
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 041bfa412aa0..81900b3cbe37 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -25,6 +25,7 @@ struct platform_device {
 	bool		id_auto;
 	struct device	dev;
 	u64		platform_dma_mask;
+	struct device_dma_parameters dma_parms;
 	u32		num_resources;
 	struct resource	*resource;
 
-- 
2.20.1

[PATCH v2 2/2] amba: Initialize dma_parms for amba devices

[Ulf Hansson]

It's currently the amba driver's responsibility to initialize the pointer,
dma_parms, for its corresponding struct device. The benefit with this
approach allows us to avoid the initialization and to not waste memory for
the struct device_dma_parameters, as this can be decided on a case by case
basis.

However, it has turned out that this approach is not very practical. Not
only does it lead to open coding, but also to real errors. In principle
callers of dma_set_max_seg_size() doesn't check the error code, but just
assumes it succeeds.

For these reasons, let's do the initialization from the common amba bus at
the device registration point. This also follows the way the PCI devices
are being managed, see pci_device_add().

Suggested-by: Christoph Hellwig <hch@lst.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

Changes in v2:
	- Move initialization to amba_device_initialize() to be more consistent
	with how we manage platform devices.

---
 drivers/amba/bus.c       | 1 +
 include/linux/amba/bus.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index fe1523664816..8558b629880b 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -645,6 +645,7 @@ static void amba_device_initialize(struct amba_device *dev, const char *name)
 	dev->dev.release = amba_device_release;
 	dev->dev.bus = &amba_bustype;
 	dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
+	dev->dev.dma_parms = &dev->dma_parms;
 	dev->res.name = dev_name(&dev->dev);
 }
 
diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index 26f0ecf401ea..0bbfd647f5c6 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -65,6 +65,7 @@ struct amba_device {
 	struct device		dev;
 	struct resource		res;
 	struct clk		*pclk;
+	struct device_dma_parameters dma_parms;
 	unsigned int		periphid;
 	unsigned int		cid;
 	struct amba_cs_uci_id	uci;
-- 
2.20.1

RE: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for platform devices

[BOUGH CHEN]

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@linaro.org>
> Sent: 2020年4月1日 2:39
> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rafael J . Wysocki
> <rafael@kernel.org>; linux-kernel@vger.kernel.org
> Cc: Arnd Bergmann <arnd@arndb.de>; Christoph Hellwig <hch@lst.de>;
> Russell King <linux@armlinux.org.uk>; Linus Walleij
> <linus.walleij@linaro.org>; Robin Murphy <robin.murphy@arm.com>; Vinod
> Koul <vkoul@kernel.org>; BOUGH CHEN <haibo.chen@nxp.com>; Ludovic
> Barre <ludovic.barre@st.com>; linux-arm-kernel@lists.infradead.org;
> dmaengine@vger.kernel.org; Ulf Hansson <ulf.hansson@linaro.org>;
> stable@vger.kernel.org
> Subject: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for
> platform devices
> 
> It's currently the platform driver's responsibility to initialize the pointer,
> dma_parms, for its corresponding struct device. The benefit with this
> approach allows us to avoid the initialization and to not waste memory for
> the struct device_dma_parameters, as this can be decided on a case by case
> basis.
> 
> However, it has turned out that this approach is not very practical.  Not
> only does it lead to open coding, but also to real errors. In principle callers of
> dma_set_max_seg_size() doesn't check the error code, but just assumes it
> succeeds.
> 
> For these reasons, let's do the initialization from the common platform bus
> at the device registration point. This also follows the way the PCI devices are
> being managed, see pci_device_add().
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> 

Hi Ulf,

I test both on our local 5.4.24 branch and the latest Linux-next, both works fine.

Tested-by: Haibo Chen <haibo.chen@nxp.com>

Best Regards
Haibo Chen

> ---
> 
> Changes in v2:
> 	- Move initialization to setup_pdev_dma_masks(). This means the
> 	initialization is done also in the OF path.
> 
> ---
>  drivers/base/platform.c         | 2 ++
>  include/linux/platform_device.h | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c index
> b5ce7b085795..c81b68d5d66d 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -361,6 +361,8 @@ struct platform_object {
>   */
>  static void setup_pdev_dma_masks(struct platform_device *pdev)  {
> +	pdev->dev.dma_parms = &pdev->dma_parms;
> +
>  	if (!pdev->dev.coherent_dma_mask)
>  		pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>  	if (!pdev->dev.dma_mask) {
> diff --git a/include/linux/platform_device.h
> b/include/linux/platform_device.h index 041bfa412aa0..81900b3cbe37
> 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -25,6 +25,7 @@ struct platform_device {
>  	bool		id_auto;
>  	struct device	dev;
>  	u64		platform_dma_mask;
> +	struct device_dma_parameters dma_parms;
>  	u32		num_resources;
>  	struct resource	*resource;
> 
> --
> 2.20.1

Re: [PATCH v2 0/2] amba/platform: Initialize dma_parms at the bus level

[Ulf Hansson]

 - Greg, Arnd, Linus, etc,

On Tue, 31 Mar 2020 at 20:38, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> It's currently the amba/platform driver's responsibility to initialize the
> pointer, dma_parms, for its corresponding struct device. The benefit with this
> approach allows us to avoid the initialization and to not waste memory for the
> struct device_dma_parameters, as this can be decided on a case by case basis.
>
> However, it has turned out that this approach is not very practical. Not only
> does it lead to open coding, but also to real errors. In principle callers of
> dma_set_max_seg_size() doesn't check the error code, but just assumes it
> succeeds.
>
> For these reasons, this series initializes the dma_parms from the amba/platform
> bus at the device registration point. This also follows the way the PCI devices
> are being managed, see pci_device_add().
>
> If it turns out that this is an acceptable solution, we probably also want the
> changes for stable, but I am not sure if it applies without conflicts.
>
> The series is based on v5.6.
>
> Kind regards
> Ulf Hansson
>
>
> Ulf Hansson (2):
>   driver core: platform: Initialize dma_parms for platform devices
>   amba: Initialize dma_parms for amba devices
>
>  drivers/amba/bus.c              | 1 +
>  drivers/base/platform.c         | 2 ++
>  include/linux/amba/bus.h        | 1 +
>  include/linux/platform_device.h | 1 +
>  4 files changed, 5 insertions(+)
>
> --
> 2.20.1
>

Does this look okay or is there anything you would like me to change?

Kind regards
Uffe

Re: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for platform devices

[Arnd Bergmann]

On Tue, Mar 31, 2020 at 8:38 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> It's currently the platform driver's responsibility to initialize the
> pointer, dma_parms, for its corresponding struct device. The benefit with
> this approach allows us to avoid the initialization and to not waste memory
> for the struct device_dma_parameters, as this can be decided on a case by
> case basis.
>
> However, it has turned out that this approach is not very practical.  Not
> only does it lead to open coding, but also to real errors. In principle
> callers of dma_set_max_seg_size() doesn't check the error code, but just
> assumes it succeeds.
>
> For these reasons, let's do the initialization from the common platform bus
> at the device registration point. This also follows the way the PCI devices
> are being managed, see pci_device_add().
>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH v2 2/2] amba: Initialize dma_parms for amba devices

[Arnd Bergmann]

On Tue, Mar 31, 2020 at 8:38 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> It's currently the amba driver's responsibility to initialize the pointer,
> dma_parms, for its corresponding struct device. The benefit with this
> approach allows us to avoid the initialization and to not waste memory for
> the struct device_dma_parameters, as this can be decided on a case by case
> basis.
>
> However, it has turned out that this approach is not very practical. Not
> only does it lead to open coding, but also to real errors. In principle
> callers of dma_set_max_seg_size() doesn't check the error code, but just
> assumes it succeeds.
>
> For these reasons, let's do the initialization from the common amba bus at
> the device registration point. This also follows the way the PCI devices
> are being managed, see pci_device_add().
>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---

Reviewed-by: Arnd Bergmann <arnd@arndb.de>