Re: [PATCH v3 04/17] drm/imagination: Add skeleton PowerVR driver

[Frank Binns <Frank.Binns@imgtec.com>]

Hi Maxime,

Thank you for your feedback (comments below).

On Fri, 2023-07-07 at 14:46 +0200, Maxime Ripard wrote:
> Hi,
> 
> [I just noticed I dropped the Cc list, resending]
> 
> Thanks for contributing this driver, it's awesome to see it moving
> forward.
> 
> And congrats on the documentation too, it's not often we see a driver
> that well documented on its v3.
> 
> I've stripped some parts of the patch that weren't relevant to my
> review.
> 
> On Tue, Jun 13, 2023 at 03:47:47PM +0100, Sarah Walker wrote:
> > +static __always_inline struct pvr_device *
> > +to_pvr_device(struct drm_device *drm_dev)
> > +{
> > +     return container_of(drm_dev, struct pvr_device, base);
> > +}
> 
> For that kind of helpers, we're slowly transitioning to using a macro
> and container_of_const. This allows to work with const-ness context.

Ack

> 
> > +static int
> > +pvr_probe(struct platform_device *plat_dev)
> > +{
> > +     struct pvr_device *pvr_dev;
> > +     struct drm_device *drm_dev;
> > +     int err;
> > +
> > +     pvr_dev = devm_drm_dev_alloc(&plat_dev->dev, &pvr_drm_driver,
> > +                                  struct pvr_device, base);
> > +     if (IS_ERR(pvr_dev)) {
> > +             err = IS_ERR(pvr_dev);
> 
> PTR_ERR?

Good catch :)

> 
> > +             goto err_out;
> 
> The general pattern here is to return directly here, it's simpler to
> follow.

Ack

> 
> > +     }
> > +     drm_dev = &pvr_dev->base;
> > +
> > +     platform_set_drvdata(plat_dev, drm_dev);
> > +
> > +     err = drm_dev_register(drm_dev, 0);
> > +     if (err)
> > +             goto err_out;
> 
> I guess it would be simpler here too, but I think you're going to move
> things around anyway?
> 
> > +static const struct of_device_id dt_match[] = {
> > +     { .compatible = "ti,am62-gpu", .data = NULL },
> > +     { .compatible = "img,powervr-seriesaxe", .data = NULL },
> 
> Do you really need both? The binding you documented requires both to be
> there, so I think you can either match on the more specific one (and
> extend that list when needed) or match the more generic one and be done
> with it once and for all. Having both is redundant.

We'll drop the more specific one in the next version.

> 
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(of, dt_match);
> > +
> > +static struct platform_driver pvr_driver = {
> > +     .probe = pvr_probe,
> > +     .remove = pvr_remove,
> > +     .driver = {
> > +             .name = PVR_DRIVER_NAME,
> > +             .of_match_table = dt_match,
> > +     },
> > +};
> > +module_platform_driver(pvr_driver);
> > +
> > +MODULE_AUTHOR("Imagination Technologies Ltd.");
> > +MODULE_DESCRIPTION(PVR_DRIVER_DESC);
> > +MODULE_LICENSE("Dual MIT/GPL");
> > +MODULE_IMPORT_NS(DMA_BUF);
> > +MODULE_FIRMWARE("powervr/rogue_4.40.2.51_v1.fw");
> > +MODULE_FIRMWARE("powervr/rogue_33.15.11.3_v1.fw");
> 
> That one should probably be moved to the firmware patch?

Ack

> 
> > diff --git a/drivers/gpu/drm/imagination/pvr_drv.h b/drivers/gpu/drm/imagination/pvr_drv.h
> > new file mode 100644
> > index 000000000000..8e6f4a4dde3f
> > --- /dev/null
> > +++ b/drivers/gpu/drm/imagination/pvr_drv.h
> > @@ -0,0 +1,22 @@
> > +/* SPDX-License-Identifier: GPL-2.0 OR MIT */
> > +/* Copyright (c) 2022 Imagination Technologies Ltd. */
> > +
> > +#ifndef PVR_DRV_H
> > +#define PVR_DRV_H
> > +
> > +#include "linux/compiler_attributes.h"
> > +#include <uapi/drm/pvr_drm.h>
> > +
> > +#define PVR_DRIVER_NAME "powervr"
> > +#define PVR_DRIVER_DESC "Imagination PowerVR Graphics"
> 
> Do you intend to support the SGX and Rogue GPUs with this driver? If
> not, mentioning the generation/architecture name somewhere would be
> nice.

We don't currently have any plans to support SGX ourselves, so we'll update
this, and any other places, to clarify things.

Thanks
Frank

> 
> Maxime