linux-kernel - Re: [PATCH v9 03/12] mtd: intel-dg: implement region enumeration

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Message-ID: <aCXb1NjwGquN6vGN@black.fi.intel.com>
Date: Thu, 15 May 2025 15:19:32 +0300
From: Raag Jadav <raag.jadav@...el.com>
To: "Usyskin, Alexander" <alexander.usyskin@...el.com>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	"De Marchi, Lucas" <lucas.demarchi@...el.com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	"Vivi, Rodrigo" <rodrigo.vivi@...el.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>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	"Poosa, Karthik" <karthik.poosa@...el.com>,
	"Abliyev, Reuven" <reuven.abliyev@...el.com>,
	"Weil, Oren jer" <oren.jer.weil@...el.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"intel-xe@...ts.freedesktop.org" <intel-xe@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tomas Winkler <tomasw@...il.com>
Subject: Re: [PATCH v9 03/12] mtd: intel-dg: implement region enumeration

On Thu, May 15, 2025 at 04:53:38PM +0530, Usyskin, Alexander wrote:
> > On Thu, Apr 24, 2025 at 04:25:27PM +0300, Alexander Usyskin wrote:
> > > In intel-dg, there is no access to the spi controller,
> > > the information is extracted from the descriptor region.
> > 
> > ...
> > 
> > > @@ -22,9 +24,199 @@ struct intel_dg_nvm {
> > >  		u8 id;
> > >  		u64 offset;
> > >  		u64 size;
> > > +		unsigned int is_readable:1;
> > > +		unsigned int is_writable:1;
> > >  	} regions[] __counted_by(nregions);
> > >  };
> > >
> > > +#define NVM_TRIGGER_REG       0x00000000
> > > +#define NVM_VALSIG_REG        0x00000010
> > > +#define NVM_ADDRESS_REG       0x00000040
> > > +#define NVM_REGION_ID_REG     0x00000044
> > > +/*
> > > + * [15:0]-Erase size = 0x0010 4K 0x0080 32K 0x0100 64K
> > > + * [23:16]-Reserved
> > > + * [31:24]-Erase MEM RegionID
> > > + */
> > > +#define NVM_ERASE_REG         0x00000048
> > > +#define NVM_ACCESS_ERROR_REG  0x00000070
> > > +#define NVM_ADDRESS_ERROR_REG 0x00000074
> > > +
> > > +/* Flash Valid Signature */
> > > +#define NVM_FLVALSIG          0x0FF0A55A
> > > +
> > > +#define NVM_MAP_ADDR_MASK     GENMASK(7, 0)
> > > +#define NVM_MAP_ADDR_SHIFT    0x00000004
> > > +
> > > +#define NVM_REGION_ID_DESCRIPTOR  0
> > > +/* Flash Region Base Address */
> > > +#define NVM_FRBA      0x40
> > > +/* Flash Region __n - Flash Descriptor Record */
> > > +#define NVM_FLREG(__n) (NVM_FRBA + ((__n) * 4))
> > > +/*  Flash Map 1 Register */
> > > +#define NVM_FLMAP1_REG  0x18
> > > +#define NVM_FLMSTR4_OFFSET 0x00C
> > > +
> > > +#define NVM_ACCESS_ERROR_PCIE_MASK 0x7
> > > +
> > > +#define NVM_FREG_BASE_MASK GENMASK(15, 0)
> > > +#define NVM_FREG_ADDR_MASK GENMASK(31, 16)
> > > +#define NVM_FREG_ADDR_SHIFT 12
> > > +#define NVM_FREG_MIN_REGION_SIZE 0xFFF
> > 
> > Should we move these to a header?
> They are used only in this file, not shared to anyone, why to put in header?

If we know we won't be further expanding/splitting, sure.

...

> > > +static bool idg_nvm_region_readable(u32 access_map, u8 region)
> > > +{
> > > +	if (region < 12)
> > 
> > Anything special about 12? Should it have a macro def somewhere?
> > 
> 
> The access bits are separated for first 12 regions and last 4.
> My feeling that making below numbers #define will make
> code less readable.

Then perhaps a small comment would be useful.

> > > +		return access_map & BIT(region + 8); /* [19:8] */
> > > +	else
> > > +		return access_map & BIT(region - 12); /* [3:0] */
> > > +}
> > > +
> > > +static bool idg_nvm_region_writable(u32 access_map, u8 region)
> > > +{
> > > +	if (region < 12)

Ditto.

> > > +		return access_map & BIT(region + 20); /* [31:20] */
> > > +	else
> > > +		return access_map & BIT(region - 8); /* [7:4] */
> > > +}

Raag