linux-kernel - Re: [PATCH v2] xen: Stop abusing DT of_dma

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Date:   Thu, 10 Oct 2019 09:59:26 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Oleksandr Andrushchenko <Oleksandr_Andrushchenko@...m.com>,
        Rob Herring <robh@...nel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Robin Murphy <robin.murphy@....com>,
        Julien Grall <julien.grall@....com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] xen: Stop abusing DT of_dma_configure API

On 10/9/19 7:42 AM, Oleksandr Andrushchenko wrote:
> On 10/8/19 10:41 PM, Rob Herring wrote:
>> As the removed comments say, these aren't DT based devices.
>> of_dma_configure() is going to stop allowing a NULL DT node and calling
>> it will no longer work.
>>
>> The comment is also now out of date as of commit 9ab91e7c5c51 ("arm64:
>> default to the direct mapping in get_arch_dma_ops"). Direct mapping
>> is now the default rather than dma_dummy_ops.
>>
>> According to Stefano and Oleksandr, the only other part needed is
>> setting the DMA masks and there's no reason to restrict the masks to
>> 32-bits. So set the masks to 64 bits.
>>
>> Cc: Robin Murphy <robin.murphy@....com>
>> Cc: Julien Grall <julien.grall@....com>
>> Cc: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>> Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
>> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> Cc: Juergen Gross <jgross@...e.com>
>> Cc: Stefano Stabellini <sstabellini@...nel.org>
>> Cc: Christoph Hellwig <hch@....de>
>> Cc: xen-devel@...ts.xenproject.org
>> Signed-off-by: Rob Herring <robh@...nel.org>
> Acked-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>


Is this going to go via drm tree or should I pick it up for Xen tree?

-boris



>
> Unfortunately I cannot test this patch with real HW running Xen:
> I am still on 4.14 kernel which is dictated by the board's BSP and
> it is not possible to have more recent one at the moment.
> So, I hope the patch will work as intended.
>
> Thank you,
> Oleksandr
>> ---
>> v2:
>>   - Setup dma masks
>>   - Also fix xen_drm_front.c
>>   
>> This can now be applied to the Xen tree independent of the coming
>> of_dma_configure() changes.
>>
>> Rob
>>
>>   drivers/gpu/drm/xen/xen_drm_front.c | 12 ++----------
>>   drivers/xen/gntdev.c                | 13 ++-----------
>>   2 files changed, 4 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
>> index ba1828acd8c9..4be49c1aef51 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
>> @@ -718,17 +718,9 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
>>   	struct device *dev = &xb_dev->dev;
>>   	int ret;
>>   
>> -	/*
>> -	 * The device is not spawn from a device tree, so arch_setup_dma_ops
>> -	 * is not called, thus leaving the device with dummy DMA ops.
>> -	 * This makes the device return error on PRIME buffer import, which
>> -	 * is not correct: to fix this call of_dma_configure() with a NULL
>> -	 * node to set default DMA ops.
>> -	 */
>> -	dev->coherent_dma_mask = DMA_BIT_MASK(32);
>> -	ret = of_dma_configure(dev, NULL, true);
>> +	ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
>>   	if (ret < 0) {
>> -		DRM_ERROR("Cannot setup DMA ops, ret %d", ret);
>> +		DRM_ERROR("Cannot setup DMA mask, ret %d", ret);
>>   		return ret;
>>   	}
>>   
>> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
>> index a446a7221e13..81401f386c9c 100644
>> --- a/drivers/xen/gntdev.c
>> +++ b/drivers/xen/gntdev.c
>> @@ -22,6 +22,7 @@
>>   
>>   #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
>>   
>> +#include <linux/dma-mapping.h>
>>   #include <linux/module.h>
>>   #include <linux/kernel.h>
>>   #include <linux/init.h>
>> @@ -34,9 +35,6 @@
>>   #include <linux/slab.h>
>>   #include <linux/highmem.h>
>>   #include <linux/refcount.h>
>> -#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>> -#include <linux/of_device.h>
>> -#endif
>>   
>>   #include <xen/xen.h>
>>   #include <xen/grant_table.h>
>> @@ -625,14 +623,7 @@ static int gntdev_open(struct inode *inode, struct file *flip)
>>   	flip->private_data = priv;
>>   #ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>>   	priv->dma_dev = gntdev_miscdev.this_device;
>> -
>> -	/*
>> -	 * The device is not spawn from a device tree, so arch_setup_dma_ops
>> -	 * is not called, thus leaving the device with dummy DMA ops.
>> -	 * Fix this by calling of_dma_configure() with a NULL node to set
>> -	 * default DMA ops.
>> -	 */
>> -	of_dma_configure(priv->dma_dev, NULL, true);
>> +	dma_coerce_mask_and_coherent(priv->dma_dev, DMA_BIT_MASK(64));
>>   #endif
>>   	pr_debug("priv %p\n", priv);
>>