| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <bdf5b4f9-d6f5-419d-9465-4f722bac06ef@arm.com>
Date: Fri, 19 Dec 2025 15:31:21 +0000
From: Steven Price <steven.price@....com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
Boris Brezillon <boris.brezillon@...labora.com>,
Liviu Dudau <liviu.dudau@....com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Matthias Brugger
<matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: Chen-Yu Tsai <wenst@...omium.org>, Chia-I Wu <olvaffe@...il.com>,
kernel@...labora.com, dri-devel@...ts.freedesktop.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/4] drm/panthor: Implement reading shader_present from
nvmem
On 17/12/2025 17:03, Nicolas Frattaroli wrote:
> On some platforms, notably MediaTek MT8196, the shader_present bitmask
> in the Mali GPU register for it has cores enabled that may be faulty.
> The true shader_present bitmask is found in an efuse instead.
>
> Implement reading shader_present from an nvmem cell if one is present,
> falling back to the Mali register if it's absent. The error codes are
> trickled up through to the probe function so that probe deferral works.
>
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Reviewed-by: Steven Price <steven.price@....com>
[Although I really hope other vendors don't do this - the hardware is
broken!]
Although one NIT below if you respin for other reasons...
> ---
> drivers/gpu/drm/panthor/panthor_hw.c | 63 ++++++++++++++++++++++++++++++++----
> 1 file changed, 57 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_hw.c b/drivers/gpu/drm/panthor/panthor_hw.c
> index 87ebb7ae42c4..eb44c8b108aa 100644
> --- a/drivers/gpu/drm/panthor/panthor_hw.c
> +++ b/drivers/gpu/drm/panthor/panthor_hw.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0 or MIT
> /* Copyright 2025 ARM Limited. All rights reserved. */
>
> +#include <linux/nvmem-consumer.h>
> #include <drm/drm_print.h>
>
> #include "panthor_device.h"
> @@ -109,7 +110,52 @@ static char *get_gpu_model_name(struct panthor_device *ptdev)
> return "(Unknown Mali GPU)";
> }
>
> -static void panthor_gpu_info_init(struct panthor_device *ptdev)
> +static int overload_shader_present(struct panthor_device *ptdev)
> +{
> + struct device *dev = ptdev->base.dev;
> + struct nvmem_cell *cell = nvmem_cell_get(dev, "shader-present");
> + ssize_t len;
> + void *buf;
> + int ret;
> +
> + if (IS_ERR(cell)) {
> + /* On platforms without this cell, use the Mali register */
> + if (PTR_ERR(cell) == -ENOENT)
> + return 0;
> +
> + return dev_err_probe(dev, PTR_ERR(cell),
> + "Failed to get shader-present nvmem cell\n");
> + }
> +
> + buf = nvmem_cell_read(cell, &len);
> + if (IS_ERR(buf)) {
> + ret = dev_err_probe(dev, PTR_ERR(buf),
> + "Failed to read shader-present nvmem cell\n");
> + goto err_put_cell;
> + }
> +
> + if (!len || len > 8) {
> + ret = dev_err_probe(dev, -EINVAL, "shader-present cell can't be length %ld\n",
> + len);
> + goto err_free;
> + }
> +
> + memcpy(&ptdev->gpu_info.shader_present, buf, len);
> +
> + kfree(buf);
> + nvmem_cell_put(cell);
> +
> + return 0;
> +
> +err_free:
> + kfree(buf);
> +err_put_cell:
> + nvmem_cell_put(cell);
> +
> + return ret;
> +}
Rather than repeating the clean up, you can do something like:
{
void *buf = NULL;
int ret = 0
if (IS_ERR(cell)) {
ret = dev_err_probe(...);
goto out;
}
buf = nvmem_cell_read();
if (IS_ERR(buf)) {
ret = dev_err_probe(...);
goto out;
}
if (!len || len > 8) {
ret = dev_err_probe(...);
goto out;
}
memcpy();
out:
if (!IS_ERR(buf))
kfree(buf);
if (!IS_ERR(cell))
nvmem_cell_put(cell);
return ret;
}
That avoids mistakes when adding a new operation into the sequence. Or
you can use the fancy new cleanup helpers, but that feels overkill here.
But equally I'm ok if you leave the code as is - it's simple enough and
the conversation can be done later if we need it.
Thanks,
Steve
> +
> +static int panthor_gpu_info_init(struct panthor_device *ptdev)
> {
> unsigned int i;
>
> @@ -143,13 +189,18 @@ static void panthor_gpu_info_init(struct panthor_device *ptdev)
> ptdev->gpu_info.tiler_present = gpu_read64(ptdev, GPU_TILER_PRESENT);
> ptdev->gpu_info.l2_present = gpu_read64(ptdev, GPU_L2_PRESENT);
> }
> +
> + return overload_shader_present(ptdev);
> }
>
> -static void panthor_hw_info_init(struct panthor_device *ptdev)
> +static int panthor_hw_info_init(struct panthor_device *ptdev)
> {
> u32 major, minor, status;
> + int ret;
>
> - panthor_gpu_info_init(ptdev);
> + ret = panthor_gpu_info_init(ptdev);
> + if (ret)
> + return ret;
>
> major = GPU_VER_MAJOR(ptdev->gpu_info.gpu_id);
> minor = GPU_VER_MINOR(ptdev->gpu_info.gpu_id);
> @@ -172,6 +223,8 @@ static void panthor_hw_info_init(struct panthor_device *ptdev)
> "shader_present=0x%0llx l2_present=0x%0llx tiler_present=0x%0llx",
> ptdev->gpu_info.shader_present, ptdev->gpu_info.l2_present,
> ptdev->gpu_info.tiler_present);
> +
> + return 0;
> }
>
> static int panthor_hw_bind_device(struct panthor_device *ptdev)
> @@ -218,7 +271,5 @@ int panthor_hw_init(struct panthor_device *ptdev)
> if (ret)
> return ret;
>
> - panthor_hw_info_init(ptdev);
> -
> - return 0;
> + return panthor_hw_info_init(ptdev);
> }
>
Powered by blists - more mailing lists