linux-kernel - Re: [PATCH v3 3/4] drm/radeon: Raise msi_addr_mask to dma

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Message-ID: <16fc7a46-92d3-4f17-b02f-ce038796b6b0@amd.com>
Date: Fri, 23 Jan 2026 14:41:51 +0100
From: Christian König <christian.koenig@....com>
To: Vivian Wang <wangruikang@...as.ac.cn>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
 Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, "Creeley, Brett" <bcreeley@....com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Bjorn Helgaas <bhelgaas@...gle.com>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>
Cc: Han Gao <gaohan@...as.ac.cn>, Thomas Gleixner <tglx@...nel.org>,
 linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 netdev@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-riscv@...ts.infradead.org,
 sophgo@...ts.linux.dev
Subject: Re: [PATCH v3 3/4] drm/radeon: Raise msi_addr_mask to dma_bits

On 1/23/26 07:07, Vivian Wang wrote:
> The code was originally written using no_64bit_msi, which restricts the
> device to 32-bit MSI addresses.
> 
> Since msi_addr_mask is introduced, use DMA_BIT_MASK(dma_bits) instead of
> DMA_BIT_MASK(32) here for msi_addr_mask, describing the restriction more
> precisely and allowing these devices to work on platforms with MSI
> doorbell address above 32-bit space, as long as it is within the
> hardware's addressable space.
> 
> Signed-off-by: Vivian Wang <wangruikang@...as.ac.cn>

Looks reasonable to me, Reviewed-by: Christian König <christian.koenig@....com>

But please note that this is rather old HW which we don't have around for testing any more.

So should anybody complain about regressions we are probably going to have to revert that patch without further investigation.

Regards,
Christian.

> 
> ---
> v3: No changes
> ---
>  drivers/gpu/drm/radeon/radeon_device.c  |  1 +
>  drivers/gpu/drm/radeon/radeon_irq_kms.c | 10 ----------
>  2 files changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 60afaa8e56b4..5faae0361361 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1374,6 +1374,7 @@ int radeon_device_init(struct radeon_device *rdev,
>  		pr_warn("radeon: No suitable DMA available\n");
>  		return r;
>  	}
> +	rdev->pdev->msi_addr_mask = DMA_BIT_MASK(dma_bits);
>  	rdev->need_swiotlb = drm_need_swiotlb(dma_bits);
>  
>  	/* Registers mapping */
> diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
> index d550554a6f3f..839d619e5602 100644
> --- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
> +++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
> @@ -245,16 +245,6 @@ static bool radeon_msi_ok(struct radeon_device *rdev)
>  	if (rdev->flags & RADEON_IS_AGP)
>  		return false;
>  
> -	/*
> -	 * Older chips have a HW limitation, they can only generate 40 bits
> -	 * of address for "64-bit" MSIs which breaks on some platforms, notably
> -	 * IBM POWER servers, so we limit them
> -	 */
> -	if (rdev->family < CHIP_BONAIRE) {
> -		dev_info(rdev->dev, "radeon: MSI limited to 32-bit\n");
> -		rdev->pdev->msi_addr_mask = DMA_BIT_MASK(32);
> -	}
> -
>  	/* force MSI on */
>  	if (radeon_msi == 1)
>  		return true;
>