[PATCH] staging: vchiq_arm: Add 36-bit address support

[PATCH] staging: vchiq_arm: Add 36-bit address support

[Mwesigwa Guma]

Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Ojaswin Mujoo <ojaswin98@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Amarjargal Gundjalam <amarjargal16@gmail.com>
Cc: Phil Elwell <phil@raspberrypi.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: linux-rpi-kernel@lists.infradead.org 
Cc: linux-arm-kernel@lists.infradead.org 
Cc: linux-staging@lists.linux.dev 
Cc: fedora-rpi@googlegroups.com
Cc: Joel Savitz <jsavitz@redhat.com>
Cc: Chukpozohn Toe <ctoe@redhat.com>
Cc: Clark Williams <clark@redhat.com>

This is a forward port of Phil Elwell's commit from the Raspberry Pi
Linux fork described as follows [1]:

    Conditional on a new compatible string, change the pagelist encoding
    such that the top 24 bits are the pfn, leaving 8 bits for run length
    (-1), giving a 36-bit address range.
    
    Manage the split between addresses for the VPU and addresses for the
    40-bit DMA controller with a dedicated DMA device pointer that on non-
    BCM2711 platforms is the same as the main VCHIQ device. This allows
    the VCHIQ node to stay in the usual place in the DT.

This commit enables VCHIQ device access on a Raspberry Pi 4B running the 
mainline Linux kernel.

Tested on Fedora Linux running on a Raspberry Pi 4B.

[1]: https://github.com/raspberrypi/linux/commit/97268fd23eb8d08dc74eac5e3fd697303de26610

Signed-off-by: Mwesigwa Guma <mguma@redhat.com>
---
 .../interface/vchiq_arm/vchiq_arm.c           | 131 +++++++++++++++---
 .../interface/vchiq_arm/vchiq_arm.h           |   1 +
 2 files changed, 109 insertions(+), 23 deletions(-)

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
index b25369a13452..888526694e56 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -67,6 +67,9 @@ struct vchiq_state g_state;
 
 static struct platform_device *bcm2835_camera;
 static struct platform_device *bcm2835_audio;
+static struct platform_device *bcm2835_codec;
+static struct platform_device *vcsm_cma;
+static struct platform_device *bcm2835_isp;
 
 static struct vchiq_drvdata bcm2835_drvdata = {
 	.cache_line_size = 32,
@@ -76,6 +79,11 @@ static struct vchiq_drvdata bcm2836_drvdata = {
 	.cache_line_size = 64,
 };
 
+static struct vchiq_drvdata bcm2711_drvdata = {
+	.cache_line_size = 64,
+	.use_36bit_addrs = true,
+};
+
 struct vchiq_2835_state {
 	int inited;
 	struct vchiq_arm_state arm_state;
@@ -105,11 +113,13 @@ static void __iomem *g_regs;
  * of 32.
  */
 static unsigned int g_cache_line_size = 32;
+static unsigned int g_use_36bit_addrs;
 static unsigned int g_fragments_size;
 static char *g_fragments_base;
 static char *g_free_fragments;
 static struct semaphore g_free_fragments_sema;
 static struct device *g_dev;
+static struct device *g_dma_dev;
 
 static DEFINE_SEMAPHORE(g_free_fragments_mutex);
 
@@ -139,7 +149,7 @@ static void
 cleanup_pagelistinfo(struct vchiq_pagelist_info *pagelistinfo)
 {
 	if (pagelistinfo->scatterlist_mapped) {
-		dma_unmap_sg(g_dev, pagelistinfo->scatterlist,
+		dma_unmap_sg(g_dma_dev, pagelistinfo->scatterlist,
 			     pagelistinfo->num_pages, pagelistinfo->dma_dir);
 	}
 
@@ -288,7 +298,7 @@ create_pagelist(char *buf, char __user *ubuf,
 		count -= len;
 	}
 
-	dma_buffers = dma_map_sg(g_dev,
+	dma_buffers = dma_map_sg(g_dma_dev,
 				 scatterlist,
 				 num_pages,
 				 pagelistinfo->dma_dir);
@@ -302,25 +312,61 @@ create_pagelist(char *buf, char __user *ubuf,
 
 	/* Combine adjacent blocks for performance */
 	k = 0;
-	for_each_sg(scatterlist, sg, dma_buffers, i) {
-		u32 len = sg_dma_len(sg);
-		u32 addr = sg_dma_address(sg);
+	if (g_use_36bit_addrs) {
+		for_each_sg(scatterlist, sg, dma_buffers, i) {
+			u32 len = sg_dma_len(sg);
+			u64 addr = sg_dma_address(sg);
+			u32 page_id = (u32)((addr >> 4) & ~0xff);
+			u32 sg_pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+			/* Note: addrs is the address + page_count - 1
+			 * The firmware expects blocks after the first to be page-
+			 * aligned and a multiple of the page size
+			 */
+			WARN_ON(len == 0);
+			WARN_ON(i &&
+				(i != (dma_buffers - 1)) && (len & ~PAGE_MASK));
+			WARN_ON(i && (addr & ~PAGE_MASK));
+			WARN_ON(upper_32_bits(addr) > 0xf);
+			if (k > 0 &&
+			    ((addrs[k - 1] & ~0xff) +
+			     (((addrs[k - 1] & 0xff) + 1) << 8)
+			     == page_id)) {
+				u32 inc_pages = min(sg_pages,
+						    0xff - (addrs[k - 1] & 0xff));
+				addrs[k - 1] += inc_pages;
+				page_id += inc_pages << 8;
+				sg_pages -= inc_pages;
+			}
+			while (sg_pages) {
+				u32 inc_pages = min(sg_pages, 0x100u);
 
-		/* Note: addrs is the address + page_count - 1
-		 * The firmware expects blocks after the first to be page-
-		 * aligned and a multiple of the page size
-		 */
-		WARN_ON(len == 0);
-		WARN_ON(i && (i != (dma_buffers - 1)) && (len & ~PAGE_MASK));
-		WARN_ON(i && (addr & ~PAGE_MASK));
-		if (k > 0 &&
-		    ((addrs[k - 1] & PAGE_MASK) +
-		     (((addrs[k - 1] & ~PAGE_MASK) + 1) << PAGE_SHIFT))
-		    == (addr & PAGE_MASK))
-			addrs[k - 1] += ((len + PAGE_SIZE - 1) >> PAGE_SHIFT);
-		else
-			addrs[k++] = (addr & PAGE_MASK) |
-				(((len + PAGE_SIZE - 1) >> PAGE_SHIFT) - 1);
+				addrs[k++] = page_id | (inc_pages - 1);
+				page_id += inc_pages << 8;
+				sg_pages -= inc_pages;
+			}
+		}
+	} else {
+		for_each_sg(scatterlist, sg, dma_buffers, i) {
+			u32 len = sg_dma_len(sg);
+			u32 addr = sg_dma_address(sg);
+			u32 new_pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+			/* Note: addrs is the address + page_count - 1
+			 * The firmware expects blocks after the first to be page-
+			 * aligned and a multiple of the page size
+			 */
+			WARN_ON(len == 0);
+			WARN_ON(i && (i != (dma_buffers - 1)) && (len & ~PAGE_MASK));
+			WARN_ON(i && (addr & ~PAGE_MASK));
+			if (k > 0 &&
+			    ((addrs[k - 1] & PAGE_MASK) +
+			     (((addrs[k - 1] & ~PAGE_MASK) + 1) << PAGE_SHIFT))
+			    == (addr & PAGE_MASK))
+				addrs[k - 1] += new_pages;
+			else
+				addrs[k++] = (addr & PAGE_MASK) | (new_pages - 1);
+		}
 	}
 
 	/* Partial cache lines (fragments) require special measures */
@@ -364,7 +410,7 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
 	 * NOTE: dma_unmap_sg must be called before the
 	 * cpu can touch any of the data/pages.
 	 */
-	dma_unmap_sg(g_dev, pagelistinfo->scatterlist,
+	dma_unmap_sg(g_dma_dev, pagelistinfo->scatterlist,
 		     pagelistinfo->num_pages, pagelistinfo->dma_dir);
 	pagelistinfo->scatterlist_mapped = 0;
 
@@ -422,6 +468,7 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
 int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state *state)
 {
 	struct device *dev = &pdev->dev;
+	struct device *dma_dev = NULL;
 	struct vchiq_drvdata *drvdata = platform_get_drvdata(pdev);
 	struct rpi_firmware *fw = drvdata->fw;
 	struct vchiq_slot_zero *vchiq_slot_zero;
@@ -443,6 +490,24 @@ int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state *state)
 	g_cache_line_size = drvdata->cache_line_size;
 	g_fragments_size = 2 * g_cache_line_size;
 
+	if (drvdata->use_36bit_addrs) {
+		struct device_node *dma_node =
+			of_find_compatible_node(NULL, NULL, "brcm,bcm2711-dma");
+
+		if (dma_node) {
+			struct platform_device *pdev;
+
+			pdev = of_find_device_by_node(dma_node);
+			if (pdev)
+				dma_dev = &pdev->dev;
+			of_node_put(dma_node);
+			g_use_36bit_addrs = true;
+		} else {
+			dev_err(dev, "40-bit DMA controller not found\n");
+			return -EINVAL;
+		}
+	}
+
 	/* Allocate space for the channels in coherent memory */
 	slot_mem_size = PAGE_ALIGN(TOTAL_SLOTS * VCHIQ_SLOT_SIZE);
 	frag_mem_size = PAGE_ALIGN(g_fragments_size * MAX_FRAGMENTS);
@@ -455,13 +520,14 @@ int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state *state)
 	}
 
 	WARN_ON(((unsigned long)slot_mem & (PAGE_SIZE - 1)) != 0);
+	channelbase = slot_phys;
 
 	vchiq_slot_zero = vchiq_init_slots(slot_mem, slot_mem_size);
 	if (!vchiq_slot_zero)
 		return -EINVAL;
 
 	vchiq_slot_zero->platform_data[VCHIQ_PLATFORM_FRAGMENTS_OFFSET_IDX] =
-		(int)slot_phys + slot_mem_size;
+		channelbase + slot_mem_size;
 	vchiq_slot_zero->platform_data[VCHIQ_PLATFORM_FRAGMENTS_COUNT_IDX] =
 		MAX_FRAGMENTS;
 
@@ -495,7 +561,6 @@ int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state *state)
 	}
 
 	/* Send the base address of the slots to VideoCore */
-	channelbase = slot_phys;
 	err = rpi_firmware_property(fw, RPI_FIRMWARE_VCHIQ_INIT,
 				    &channelbase, sizeof(channelbase));
 	if (err || channelbase) {
@@ -504,6 +569,8 @@ int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state *state)
 	}
 
 	g_dev = dev;
+	g_dma_dev = dma_dev ?: dev;
+
 	vchiq_log_info(vchiq_arm_log_level,
 		"vchiq_init - done (slots %pK, phys %pad)",
 		vchiq_slot_zero, &slot_phys);
@@ -1746,6 +1813,7 @@ void vchiq_platform_conn_state_changed(struct vchiq_state *state,
 static const struct of_device_id vchiq_of_match[] = {
 	{ .compatible = "brcm,bcm2835-vchiq", .data = &bcm2835_drvdata },
 	{ .compatible = "brcm,bcm2836-vchiq", .data = &bcm2836_drvdata },
+	{ .compatible = "brcm,bcm2711-vchiq", .data = &bcm2711_drvdata },
 	{},
 };
 MODULE_DEVICE_TABLE(of, vchiq_of_match);
@@ -1755,6 +1823,7 @@ vchiq_register_child(struct platform_device *pdev, const char *name)
 {
 	struct platform_device_info pdevinfo;
 	struct platform_device *child;
+	struct device_node *np;
 
 	memset(&pdevinfo, 0, sizeof(pdevinfo));
 
@@ -1763,12 +1832,22 @@ vchiq_register_child(struct platform_device *pdev, const char *name)
 	pdevinfo.id = PLATFORM_DEVID_NONE;
 	pdevinfo.dma_mask = DMA_BIT_MASK(32);
 
+	np = of_get_child_by_name(pdev->dev.of_node, name);
+
+	/* Skip the child if it is explicitly disabled */
+	if (np && !of_device_is_available(np))
+		return NULL;
+
 	child = platform_device_register_full(&pdevinfo);
 	if (IS_ERR(child)) {
 		dev_warn(&pdev->dev, "%s not registered\n", name);
 		child = NULL;
 	}
 
+	child->dev.of_node = np;
+
+	of_dma_configure(&child->dev, np, true);
+
 	return child;
 }
 
@@ -1819,8 +1898,11 @@ static int vchiq_probe(struct platform_device *pdev)
 		goto error_exit;
 	}
 
+	vcsm_cma = vchiq_register_child(pdev, "vcsm-cma");
+	bcm2835_codec = vchiq_register_child(pdev, "bcm2835-codec");
 	bcm2835_camera = vchiq_register_child(pdev, "bcm2835-camera");
 	bcm2835_audio = vchiq_register_child(pdev, "bcm2835_audio");
+	bcm2835_isp = vchiq_register_child(pdev, "bcm2835-isp");
 
 	return 0;
 
@@ -1832,8 +1914,11 @@ static int vchiq_probe(struct platform_device *pdev)
 
 static int vchiq_remove(struct platform_device *pdev)
 {
+	platform_device_unregister(bcm2835_isp);
 	platform_device_unregister(bcm2835_audio);
 	platform_device_unregister(bcm2835_camera);
+	platform_device_unregister(bcm2835_codec);
+	platform_device_unregister(vcsm_cma);
 	vchiq_debugfs_deinit();
 	vchiq_deregister_chrdev();
 
diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
index e8e39a154c74..b7653e8ce9e0 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
@@ -61,6 +61,7 @@ struct vchiq_arm_state {
 
 struct vchiq_drvdata {
 	const unsigned int cache_line_size;
+	const bool use_36bit_addrs;
 	struct rpi_firmware *fw;
 };
 
-- 
2.31.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] staging: vchiq_arm: Add 36-bit address support

[Dan Carpenter]

On Thu, Oct 14, 2021 at 06:32:30PM -0400, Mwesigwa Guma wrote:
> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Stefan Wahren <stefan.wahren@i2se.com>
> Cc: Ojaswin Mujoo <ojaswin98@gmail.com>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Amarjargal Gundjalam <amarjargal16@gmail.com>
> Cc: Phil Elwell <phil@raspberrypi.com>
> Cc: bcm-kernel-feedback-list@broadcom.com
> Cc: linux-rpi-kernel@lists.infradead.org 
> Cc: linux-arm-kernel@lists.infradead.org 
> Cc: linux-staging@lists.linux.dev 
> Cc: fedora-rpi@googlegroups.com
> Cc: Joel Savitz <jsavitz@redhat.com>
> Cc: Chukpozohn Toe <ctoe@redhat.com>
> Cc: Clark Williams <clark@redhat.com>
> 

Did you intend to put this CC list here?  It goes at the end next to
the Signed-off-by line if so.  I don't feel like it's required except
maybe Phil to show he was Cc'd.

> This is a forward port of Phil Elwell's commit from the Raspberry Pi
> Linux fork described as follows [1]:

Please use the From: header to give authorship credit.

From: Phil Elwell <phil@raspberrypi.com>

Make that the first line of the email.

> 
>     Conditional on a new compatible string, change the pagelist encoding
>     such that the top 24 bits are the pfn, leaving 8 bits for run length
>     (-1), giving a 36-bit address range.
>     
>     Manage the split between addresses for the VPU and addresses for the
>     40-bit DMA controller with a dedicated DMA device pointer that on non-
>     BCM2711 platforms is the same as the main VCHIQ device. This allows
>     the VCHIQ node to stay in the usual place in the DT.
> 
> This commit enables VCHIQ device access on a Raspberry Pi 4B running the 
> mainline Linux kernel.
> 
> Tested on Fedora Linux running on a Raspberry Pi 4B.
> 
> [1]: https://github.com/raspberrypi/linux/commit/97268fd23eb8d08dc74eac5e3fd697303de26610
> 
> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>

regards,
dan carpenter


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] staging: vchiq_arm: Add 36-bit address support

[nicolas saenz julienne]

Hi Mwesigwa,

On Thu, 2021-10-14 at 18:32 -0400, Mwesigwa Guma wrote:
> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Stefan Wahren <stefan.wahren@i2se.com>
> Cc: Ojaswin Mujoo <ojaswin98@gmail.com>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Amarjargal Gundjalam <amarjargal16@gmail.com>
> Cc: Phil Elwell <phil@raspberrypi.com>
> Cc: bcm-kernel-feedback-list@broadcom.com
> Cc: linux-rpi-kernel@lists.infradead.org 
> Cc: linux-arm-kernel@lists.infradead.org 
> Cc: linux-staging@lists.linux.dev 
> Cc: fedora-rpi@googlegroups.com
> Cc: Joel Savitz <jsavitz@redhat.com>
> Cc: Chukpozohn Toe <ctoe@redhat.com>
> Cc: Clark Williams <clark@redhat.com>
> 
> This is a forward port of Phil Elwell's commit from the Raspberry Pi
> Linux fork described as follows [1]:
> 
>     Conditional on a new compatible string, change the pagelist encoding
>     such that the top 24 bits are the pfn, leaving 8 bits for run length
>     (-1), giving a 36-bit address range.
>     
>     Manage the split between addresses for the VPU and addresses for the
>     40-bit DMA controller with a dedicated DMA device pointer that on non-
>     BCM2711 platforms is the same as the main VCHIQ device. This allows
>     the VCHIQ node to stay in the usual place in the DT.
> 
> This commit enables VCHIQ device access on a Raspberry Pi 4B running the 
> mainline Linux kernel.
> 
> Tested on Fedora Linux running on a Raspberry Pi 4B.
> 
> [1]: https://github.com/raspberrypi/linux/commit/97268fd23eb8d08dc74eac5e3fd697303de26610
> 
> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>

I see a lot happening on this patch. You're:

 - Registering a number of child devices that don't seem to exist upstream
   ('vcsm-cma', 'bcm2835-codec', and 'bcm2825-isp').
 - Updating vchiq_register_child(). 
 - Adding brcm,bcm2711-vchiq's compatible string (no dt bindings? see
   Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt).
 - Looking for 'brcm,bcm2711-dma' in the devicetree.
 - Using 'brcm,bcm2711-dma's' device node to re-generate the page lists.

Each one of these should at least be a separate patch, which proper
justification[1]. You can't just take downstream fixes, rebase them and send
them upstream. You really have to own them, undestand what's happening and
repurpose everything so it's up to standard even if it means diverging from
what downstream is doing.

Regards,
Nicolas

[1] Have a look at Documentation/process/submitting-patches.rst.


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] staging: vchiq_arm: Add 36-bit address support

[Stefan Wahren]

Hi Mwesigwa,

additional to Nicolas' comments.

Am 15.10.21 um 10:19 schrieb nicolas saenz julienne:
> Hi Mwesigwa,
>
> On Thu, 2021-10-14 at 18:32 -0400, Mwesigwa Guma wrote:
>> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Stefan Wahren <stefan.wahren@i2se.com>
>> Cc: Ojaswin Mujoo <ojaswin98@gmail.com>
>> Cc: Dan Carpenter <dan.carpenter@oracle.com>
>> Cc: Amarjargal Gundjalam <amarjargal16@gmail.com>
>> Cc: Phil Elwell <phil@raspberrypi.com>
>> Cc: bcm-kernel-feedback-list@broadcom.com
>> Cc: linux-rpi-kernel@lists.infradead.org 
>> Cc: linux-arm-kernel@lists.infradead.org 
>> Cc: linux-staging@lists.linux.dev 
>> Cc: fedora-rpi@googlegroups.com
>> Cc: Joel Savitz <jsavitz@redhat.com>
>> Cc: Chukpozohn Toe <ctoe@redhat.com>
>> Cc: Clark Williams <clark@redhat.com>
>>
>> This is a forward port of Phil Elwell's commit from the Raspberry Pi
>> Linux fork described as follows [1]:
>>
>>     Conditional on a new compatible string, change the pagelist encoding
>>     such that the top 24 bits are the pfn, leaving 8 bits for run length
>>     (-1), giving a 36-bit address range.
>>     
>>     Manage the split between addresses for the VPU and addresses for the
>>     40-bit DMA controller with a dedicated DMA device pointer that on non-
>>     BCM2711 platforms is the same as the main VCHIQ device. This allows
>>     the VCHIQ node to stay in the usual place in the DT.
From my understanding this also requires changes to the DMA driver (40
bit support) and the BCM2711 dts files, which are also not upstream yet
(the DMA changes not the files itself).
>>
>> This commit enables VCHIQ device access on a Raspberry Pi 4B running the 
>> mainline Linux kernel.
>>
>> Tested on Fedora Linux running on a Raspberry Pi 4B.
>>
>> [1]: https://github.com/raspberrypi/linux/commit/97268fd23eb8d08dc74eac5e3fd697303de26610
>>
>> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>
> I see a lot happening on this patch. You're:
>
>  - Registering a number of child devices that don't seem to exist upstream
>    ('vcsm-cma', 'bcm2835-codec', and 'bcm2825-isp').
>  - Updating vchiq_register_child(). 
>  - Adding brcm,bcm2711-vchiq's compatible string (no dt bindings? see
>    Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt).
In order to get this part accepted, i send a series to convert the
dt-binding to YAML format.
>  - Looking for 'brcm,bcm2711-dma' in the devicetree.
>  - Using 'brcm,bcm2711-dma's' device node to re-generate the page lists.
>
> Each one of these should at least be a separate patch, which proper
> justification[1]. You can't just take downstream fixes, rebase them and send
> them upstream. You really have to own them, undestand what's happening and
> repurpose everything so it's up to standard even if it means diverging from
> what downstream is doing.

AFAIU it's preferred to get this driver out of staging (take a look at
the TODO file) before implementing new features.

Best regards

>
> Regards,
> Nicolas
>
> [1] Have a look at Documentation/process/submitting-patches.rst.
>


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel