[PATCH] bcma: get SoC device struct & assign dma_mask

[PATCH] bcma: get SoC device struct & assign dma_mask

[Florian Fainelli]

From: Rafał Miłecki <rafal@milecki.pl>

For bus devices to be fully usable it's required to set their DMA
parameters.

For years it has been missing and remained unnoticed because of
mips_dma_alloc_coherent() silently handling the empty coherent_dma_mask.
Kernel 4.19 came with a lot of DMA changes and caused a regression on
the bcm47xx. Starting with the commit f8c55dc6e828 ("MIPS: use generic
dma noncoherent ops for simple noncoherent platforms") DMA coherent
allocations just fail. Example:
[    1.114914] bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
[    1.121215] bgmac_bcma bcma0:2: Unable to alloc memory for DMA
[    1.127626] bgmac_bcma: probe of bcma0:2 failed with error -12
[    1.133838] bgmac_bcma: Broadcom 47xx GBit MAC driver loaded

This change fixes above regression in addition to the MIPS bcm47xx
commit 321c46b91550 ("MIPS: BCM47XX: Setup struct device for the SoC").

It also fixes another *old* GPIO regression caused by a parent pointing
to the NULL:
[    0.157054] missing gpiochip .dev parent pointer
[    0.157287] bcma: bus0: Error registering GPIO driver: -22
introduced by the commit 74f4e0cc6108 ("bcma: switch GPIO portions to
use GPIOLIB_IRQCHIP").

Fixes: f8c55dc6e828 ("MIPS: use generic dma noncoherent ops for simple noncoherent platforms")
Fixes: 74f4e0cc6108 ("bcma: switch GPIO portions to use GPIOLIB_IRQCHIP")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-mips@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
---
Christoph,

I don't know if this is what you had in mind. I am also not sure if we
should have the bcma_bus_type implement .dma_configure and set it to
platform_dma_configure?

 drivers/bcma/host_soc.c | 2 ++
 drivers/bcma/main.c     | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/bcma/host_soc.c b/drivers/bcma/host_soc.c
index 90d5bdc12e03..fd2e8ff17c76 100644
--- a/drivers/bcma/host_soc.c
+++ b/drivers/bcma/host_soc.c
@@ -191,6 +191,8 @@ int __init bcma_host_soc_init(struct bcma_soc *soc)
 	struct bcma_bus *bus = &soc->bus;
 	int err;
 
+	bus->dev = soc->dev;
+
 	/* Scan bus and initialize it */
 	err = bcma_bus_early_register(bus);
 	if (err)
diff --git a/drivers/bcma/main.c b/drivers/bcma/main.c
index 8e7ca3e4c8c4..6793c2ff60fd 100644
--- a/drivers/bcma/main.c
+++ b/drivers/bcma/main.c
@@ -253,6 +253,8 @@ void bcma_prepare_core(struct bcma_bus *bus, struct bcma_device *core)
 		if (IS_ENABLED(CONFIG_OF) && bus->dev) {
 			core->dma_dev = bus->dev;
 		} else {
+			if (!core->dev.coherent_dma_mask)
+				core->dev.coherent_dma_mask = DMA_BIT_MASK(32);
 			core->dev.dma_mask = &core->dev.coherent_dma_mask;
 			core->dma_dev = &core->dev;
 		}
-- 
2.25.1

Re: [PATCH] bcma: get SoC device struct & assign dma_mask

[Christoph Hellwig]

On Thu, Jan 06, 2022 at 08:17:44PM -0800, Florian Fainelli wrote:
> From: Rafał Miłecki <rafal@milecki.pl>
> 
> For bus devices to be fully usable it's required to set their DMA
> parameters.
> 
> For years it has been missing and remained unnoticed because of
> mips_dma_alloc_coherent() silently handling the empty coherent_dma_mask.
> Kernel 4.19 came with a lot of DMA changes and caused a regression on
> the bcm47xx. Starting with the commit f8c55dc6e828 ("MIPS: use generic
> dma noncoherent ops for simple noncoherent platforms") DMA coherent
> allocations just fail. Example:
> [    1.114914] bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
> [    1.121215] bgmac_bcma bcma0:2: Unable to alloc memory for DMA
> [    1.127626] bgmac_bcma: probe of bcma0:2 failed with error -12
> [    1.133838] bgmac_bcma: Broadcom 47xx GBit MAC driver loaded
> 
> This change fixes above regression in addition to the MIPS bcm47xx
> commit 321c46b91550 ("MIPS: BCM47XX: Setup struct device for the SoC").

How did it take so long to notice this?

> I don't know if this is what you had in mind. I am also not sure if we
> should have the bcma_bus_type implement .dma_configure and set it to
> platform_dma_configure?

Unless you have an OF tree that declares DMA limitations there is no
need to call platform_dma_configure.

> --- a/drivers/bcma/host_soc.c
> +++ b/drivers/bcma/host_soc.c
> @@ -191,6 +191,8 @@ int __init bcma_host_soc_init(struct bcma_soc *soc)
>  	struct bcma_bus *bus = &soc->bus;
>  	int err;
>  
> +	bus->dev = soc->dev;
> +
>  	/* Scan bus and initialize it */
>  	err = bcma_bus_early_register(bus);
>  	if (err)
> diff --git a/drivers/bcma/main.c b/drivers/bcma/main.c
> index 8e7ca3e4c8c4..6793c2ff60fd 100644
> --- a/drivers/bcma/main.c
> +++ b/drivers/bcma/main.c
> @@ -253,6 +253,8 @@ void bcma_prepare_core(struct bcma_bus *bus, struct bcma_device *core)
>  		if (IS_ENABLED(CONFIG_OF) && bus->dev) {
>  			core->dma_dev = bus->dev;
>  		} else {
> +			if (!core->dev.coherent_dma_mask)
> +				core->dev.coherent_dma_mask = DMA_BIT_MASK(32);

Is there any way coherent_dma_mask could already be set here?

>  			core->dev.dma_mask = &core->dev.coherent_dma_mask;
>  			core->dma_dev = &core->dev;

Not really needed for the quick fix, but pointing the dma_mask to the
coherent_dma_mask is a bad idea as it removes the often used feature
to use a different mask for the cohernent allocations vs the streaming
mappings.

Re: [PATCH] bcma: get SoC device struct & assign dma_mask

[Rafał Miłecki]

On 10.01.2022 10:09, Christoph Hellwig wrote:
> On Thu, Jan 06, 2022 at 08:17:44PM -0800, Florian Fainelli wrote:
>> From: Rafał Miłecki <rafal@milecki.pl>
>>
>> For bus devices to be fully usable it's required to set their DMA
>> parameters.
>>
>> For years it has been missing and remained unnoticed because of
>> mips_dma_alloc_coherent() silently handling the empty coherent_dma_mask.
>> Kernel 4.19 came with a lot of DMA changes and caused a regression on
>> the bcm47xx. Starting with the commit f8c55dc6e828 ("MIPS: use generic
>> dma noncoherent ops for simple noncoherent platforms") DMA coherent
>> allocations just fail. Example:
>> [    1.114914] bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
>> [    1.121215] bgmac_bcma bcma0:2: Unable to alloc memory for DMA
>> [    1.127626] bgmac_bcma: probe of bcma0:2 failed with error -12
>> [    1.133838] bgmac_bcma: Broadcom 47xx GBit MAC driver loaded
>>
>> This change fixes above regression in addition to the MIPS bcm47xx
>> commit 321c46b91550 ("MIPS: BCM47XX: Setup struct device for the SoC").
> 
> How did it take so long to notice this?

I noticed it 3 years ago and sent semi-fix that wasn't accepted (for
probably a good reason) back then:
[PATCH wireless-drivers-next] bcma: get SoC device struct & copy its DMA params to the subdevices
https://patchwork.kernel.org/project/linux-wireless/patch/20190121101121.24555-1-zajec5@gmail.com/

Since then OpenWrt carried on above fix as a downstream patch.

I guess OpenWrt is the only active user of that code.

Thanks a lot Florian for bringing that upstream.

Re: [PATCH] bcma: get SoC device struct & assign dma_mask

[Florian Fainelli]

On 1/10/22 1:09 AM, Christoph Hellwig wrote:
> On Thu, Jan 06, 2022 at 08:17:44PM -0800, Florian Fainelli wrote:
>> From: Rafał Miłecki <rafal@milecki.pl>
>>
>> For bus devices to be fully usable it's required to set their DMA
>> parameters.
>>
>> For years it has been missing and remained unnoticed because of
>> mips_dma_alloc_coherent() silently handling the empty coherent_dma_mask.
>> Kernel 4.19 came with a lot of DMA changes and caused a regression on
>> the bcm47xx. Starting with the commit f8c55dc6e828 ("MIPS: use generic
>> dma noncoherent ops for simple noncoherent platforms") DMA coherent
>> allocations just fail. Example:
>> [    1.114914] bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
>> [    1.121215] bgmac_bcma bcma0:2: Unable to alloc memory for DMA
>> [    1.127626] bgmac_bcma: probe of bcma0:2 failed with error -12
>> [    1.133838] bgmac_bcma: Broadcom 47xx GBit MAC driver loaded
>>
>> This change fixes above regression in addition to the MIPS bcm47xx
>> commit 321c46b91550 ("MIPS: BCM47XX: Setup struct device for the SoC").
> 
> How did it take so long to notice this?
> 
>> I don't know if this is what you had in mind. I am also not sure if we
>> should have the bcma_bus_type implement .dma_configure and set it to
>> platform_dma_configure?
> 
> Unless you have an OF tree that declares DMA limitations there is no
> need to call platform_dma_configure.

OK, so we may have to implement that callback then because on ARM-based
Devices we have BCMA plus Device Tree being used. Although none of those
ARM platforms define any DMA apertures or restrictions, I suppose

> 
>> --- a/drivers/bcma/host_soc.c
>> +++ b/drivers/bcma/host_soc.c
>> @@ -191,6 +191,8 @@ int __init bcma_host_soc_init(struct bcma_soc *soc)
>>  	struct bcma_bus *bus = &soc->bus;
>>  	int err;
>>  
>> +	bus->dev = soc->dev;
>> +
>>  	/* Scan bus and initialize it */
>>  	err = bcma_bus_early_register(bus);
>>  	if (err)
>> diff --git a/drivers/bcma/main.c b/drivers/bcma/main.c
>> index 8e7ca3e4c8c4..6793c2ff60fd 100644
>> --- a/drivers/bcma/main.c
>> +++ b/drivers/bcma/main.c
>> @@ -253,6 +253,8 @@ void bcma_prepare_core(struct bcma_bus *bus, struct bcma_device *core)
>>  		if (IS_ENABLED(CONFIG_OF) && bus->dev) {
>>  			core->dma_dev = bus->dev;
>>  		} else {
>> +			if (!core->dev.coherent_dma_mask)
>> +				core->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> 
> Is there any way coherent_dma_mask could already be set here?

On MIPS-based devices (not using Device Tree), I don't see a way this
could be set, however on ARM based devices, since they use Device Tree,
maybe this value could be different than 0. I will run some tests on
both types of devices and post an updated patch if relevant.

Thanks!

> 
>>  			core->dev.dma_mask = &core->dev.coherent_dma_mask;
>>  			core->dma_dev = &core->dev;
> 
> Not really needed for the quick fix, but pointing the dma_mask to the
> coherent_dma_mask is a bad idea as it removes the often used feature
> to use a different mask for the cohernent allocations vs the streaming
> mappings.

OK.
-- 
Florian