archive mirror
 help / color / mirror / Atom feed
From: Phil Elwell <>
To: Florian Fainelli <>,
	Nicolas Saenz Julienne <>,
	Rob Herring <>,
	Mark Rutland <>,
	Eric Anholt <>, Stefan Wahren <>
Subject: Re: [PATCH] ARM: dts: bcm2711: fix soc's node dma-ranges
Date: Mon, 9 Dec 2019 09:16:35 +0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 06/12/2019 18:13, Florian Fainelli wrote:
> On 12/6/19 2:16 AM, Phil Elwell wrote:
>> Hi Nicolas,
>> On 06/12/2019 00:08, Florian Fainelli wrote:
>>> On 12/4/19 4:56 AM, Nicolas Saenz Julienne wrote:
>>>> Raspberry Pi's firmware has a feature to select how much memory to
>>>> reserve for its GPU called 'gpu_mem'. The possible values go from 16MB
>>>> to 944MB, with a default of 64MB. This memory resides in the topmost
>>>> part of the lower 1GB memory area and grows bigger expanding towards the
>>>> begging of memory.
>>>> It turns out that with low 'gpu_mem' values (16MB and 32MB) the size of
>>>> the memory available to the system in the lower 1GB area can outgrow the
>>>> interconnect's dma-range as its size was selected based on the maximum
>>>> system memory available given the default gpu_mem configuration. This
>>>> makes that memory slice unavailable for DMA. And may cause nasty kernel
>>>> warnings if CMA happens to include it.
>>>> Change soc's dma-ranges to really reflect it's HW limitation, which is
>>>> being able to only DMA to the lower 1GB area.
>>>> Fixes: 7dbe8c62ceeb ("ARM: dts: Add minimal Raspberry Pi 4 support")
>>>> Signed-off-by: Nicolas Saenz Julienne <>
>>>> ---
>>>> NOTE: I'd appreciate if someone from the RPi foundation commented on
>>>> this as it's something that I'll propose to be backported to their tree.
>> The 0x3c000000 size was a mistake that arose from c0000000 + 3c000000 =
>> fc000000, but that is mixing apples and oranges (actually DMA addresses
>> and host physical addresses). Please correct it as you are proposing.
> Do you want to add an Acked-by or Reviewed-by tag to make this statement
> official?

Here you go:

Reviewed-by: Phil Elwell <>

  reply	other threads:[~2019-12-09  9:16 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-04 12:56 [PATCH] ARM: dts: bcm2711: fix soc's node dma-ranges Nicolas Saenz Julienne
2019-12-06  0:08 ` Florian Fainelli
2019-12-06 10:16   ` Phil Elwell
2019-12-06 18:13     ` Florian Fainelli
2019-12-09  9:16       ` Phil Elwell [this message]
2019-12-09 18:12 ` Florian Fainelli

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).