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[83.233.6.197]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54d6e54144esm1388050e87.93.2025.04.22.22.41.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Apr 2025 22:41:08 -0700 (PDT) Date: Wed, 23 Apr 2025 07:41:06 +0200 From: Marcus Folkesson To: Javier Martinez Canillas Cc: David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Rob Herring , Krzysztof Kozlowski , Conor Dooley , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Zimmermann Subject: Re: [PATCH v4 2/3] drm/st7571-i2c: add support for Sitronix ST7571 LCD controller Message-ID: References: <20250415-st7571-v4-0-8b5c9be8bae7@gmail.com> <20250415-st7571-v4-2-8b5c9be8bae7@gmail.com> <871ptjbxr8.fsf@minerva.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="vlQ/Rf3bjfEdQ8vd" Content-Disposition: inline In-Reply-To: <871ptjbxr8.fsf@minerva.mail-host-address-is-not-set> --vlQ/Rf3bjfEdQ8vd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Javier, On Wed, Apr 23, 2025 at 01:08:11AM +0200, Javier Martinez Canillas wrote: > Marcus Folkesson writes: >=20 > Hello Marcus, >=20 > > Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller. > > The controller has a SPI, I2C and 8bit parallel interface, this > > driver is for the I2C interface only. > > > > Reviewed-by: Thomas Zimmermann > > Signed-off-by: Marcus Folkesson > > --- >=20 > [...] >=20 > > +#define ST7571_SET_COLUMN_LSB(c) (0x00 | ((c) & 0xf)) > > +#define ST7571_SET_COLUMN_MSB(c) (0x10 | ((c) >> 4)) > > +#define ST7571_SET_COM0_LSB(x) ((x) & 0x7f) > > +#define ST7571_SET_COM0_MSB (0x44) > > +#define ST7571_SET_COM_SCAN_DIR(d) (0xc0 | (((d) << 3) & 0x8)) >=20 > You could also use the GENMASK() and FIELD_PREP() macros for these, e.g: >=20 > #define ST7571_SET_COLUMN_LSB(c) (0x00 | FIELD_PREP(GENMASK(3, 0), (c))) > #define ST7571_SET_COLUMN_MSB(c) (0x10 | FIELD_PREP(GENMASK(3, 0), (c) >= > 4)) > #define ST7571_SET_COM0_LSB(x) (FIELD_PREP(GENMASK(6, 0), (x))) > #define ST7571_SET_COM0_MSB (0x44) > #define ST7571_SET_COM_SCAN_DIR(d) (0xc0 | FIELD_PREP(GENMASK(3, 3), (d)= )) That looks better, I will change to use those macros. >=20 > [...] >=20 > Maybe a comment here that this function only exists due regmap expecting > both a .write and .read handler even for devices that are write only, e.g: Sure >=20 > /* The st7571 driver does not read registers but regmap expects a .read */ > > +static int st7571_regmap_read(void *context, const void *reg_buf, > > + size_t reg_size, void *val_buf, size_t val_size) > > +{ > > + return -EOPNOTSUPP; > > +} > > + >=20 > [...] >=20 > > +static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb,= struct drm_rect *rect) > > +{ >=20 > [...] >=20 > > + for (int y =3D rect->y1; y < rect->y2; y +=3D ST7571_PAGE_HEIGHT) { > > + for (int x =3D x1; x < x2; x++) > > + row[x] =3D st7571_transform_xy(st7571->hwbuf, x, y); > > + > > + st7571_set_position(st7571, rect->x1, y); > > + > > + /* TODO: Investige why we can't write multiple bytes at once */ > > + for (int x =3D x1; x < x2; x++) { > > + regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1); > > + > > + /* Write monochrome formats twice */ >=20 > Why this is needed ? If the display is 4bit grayscale it still expect each pixel to be written as two bits. The mapping is as follows: 0 0 =3D> White 0 1 =3D> Light gray 1 0 =3D> Dark gray 1 1 =3D> Black So here I write the data twice to get a black&white image for monochrome formats. This is not tested though, I only have a monochrome display to test with. I will extend the comment to explain this. >=20 > > + if (format =3D=3D DRM_FORMAT_R1 || format =3D=3D DRM_FORMAT_XRGB888= 8) > > + regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1); > > + } > > + } > > + > > + return 0; > > +} > > + >=20 > The driver looks great to me now, thanks a lot for taking my comments int= o account! Thanks! >=20 > Reviewed-by: Javier Martinez Canillas >=20 > --=20 > Best regards, >=20 > Javier Martinez Canillas > Core Platforms > Red Hat >=20 Best regards, Marcus Folkesson --vlQ/Rf3bjfEdQ8vd Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEBVGi6LZstU1kwSxliIBOb1ldUjIFAmgIfWsACgkQiIBOb1ld UjJrOBAAsndlQ6aC/cblkWzinnmx1bnC6BYv17GBy0hFpsliau7s7sIDAYLiGqgu U4qqJSrH3Gre8GMEnLVcPpomtng37c/JzZyl3+a+rt07kfaV1Fiq5u8gUi/aV6pm n7tD0ILy5rTecfYNzdsux062TzkQhu2KhuQPwgx+9oox5op1sY+EwF0Edm89xVZJ ajYOmmAernVvLSBLhRkwSLFaAWpyDVJ07tpWgkeYqRezaRum8PpzAobIhnVcQEOP vGtqZrTS7IO59u+J3q3W9l8i9ne+QrWI/6gPwKkNB8BrMz2mm8KEUaLkERW9dLNO yLumUxkSRzRsimDyfooL9eMqDUaHsUuhN1PEgZfrQhdYGdSgUrhgvKXqODWF/aAx BPCZxB43ctXXqt15CC9f74u/KzD7lsAvgf6WAasxYnmwkpdhjHnX03vJEkVSvnMb Rf9UyrLFuMGadiObsikIqPGWlkUM3l90S+zVNBFhTmuYB72lReyFsK8x8PsB99kg 84PIEhg607jKSoKh02Q5QdIFzhhOErTntBR7qnQSLfaDTf+4lsIurzDzmt7XH4fM phxBpj9WSPJkIt7X4A9QpYnc6olkQ+iCCunywkpFPYJZg7uJmx4HkxI9jCTGXgWJ rkY2AbyZwykY4UX2N9i3R4R1rrsvsxi2n+JB7TsucVzsZiB3nNU= =Olpq -----END PGP SIGNATURE----- --vlQ/Rf3bjfEdQ8vd--