From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukasz Majewski Subject: Re: [PATCH] dts: Disable DMA support on the BK4 vf610 device's fsl_lpuart driver Date: Wed, 9 Oct 2019 16:44:42 +0200 Message-ID: <20191009164442.51f27b9d@jawa> References: <20191009143032.9261-1-lukma@denx.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; boundary="Sig_/Di/jFXAOICs3QlZsnoXzE2z"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Robin Murphy Cc: linux-kernel@vger.kernel.org, Shawn Guo , Mark Rutland , devicetree@vger.kernel.org, Sascha Hauer , Stefan Agner , Rob Herring , Pengutronix Kernel Team , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org --Sig_/Di/jFXAOICs3QlZsnoXzE2z Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Robin, > On 09/10/2019 15:30, Lukasz Majewski wrote: > > This change disables the DMA support (RX/TX) on the NXP's fsl_lpuart > > driver - the PIO mode is used instead. This change is necessary for > > better robustness of BK4's device use cases with many potentially > > interrupted short serial transfers. > >=20 > > Without it the driver hangs when some distortion happens on UART > > lines. > >=20 > > Signed-off-by: Lukasz Majewski > > --- > > arch/arm/boot/dts/vf610-bk4.dts | 4 ++++ > > 1 file changed, 4 insertions(+) > >=20 > > diff --git a/arch/arm/boot/dts/vf610-bk4.dts > > b/arch/arm/boot/dts/vf610-bk4.dts index 0f3870d3b099..ad20f3442d40 > > 100644 --- a/arch/arm/boot/dts/vf610-bk4.dts > > +++ b/arch/arm/boot/dts/vf610-bk4.dts > > @@ -259,24 +259,28 @@ > > &uart0 { > > pinctrl-names =3D "default"; > > pinctrl-0 =3D <&pinctrl_uart0>; > > + dma-names =3D "",""; =20 >=20 > This looks like a horrible hack - is there any reason not to just > strip things at compile-time, i.e. "/delete-property/ dmas;"? I don't want to strip the dma-names property globally. I just want to adjust this particular driver mode from DMA to PIO. For my use cases - as written in the commit message - the PIO mode is more suitable (and reliable).=20 >=20 > Robin. >=20 > > status =3D "okay"; > > }; > > =20 > > &uart1 { > > pinctrl-names =3D "default"; > > pinctrl-0 =3D <&pinctrl_uart1>; > > + dma-names =3D "",""; > > status =3D "okay"; > > }; > > =20 > > &uart2 { > > pinctrl-names =3D "default"; > > pinctrl-0 =3D <&pinctrl_uart2>; > > + dma-names =3D "",""; > > status =3D "okay"; > > }; > > =20 > > &uart3 { > > pinctrl-names =3D "default"; > > pinctrl-0 =3D <&pinctrl_uart3>; > > + dma-names =3D "",""; > > status =3D "okay"; > > }; > > =20 > > =20 Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de --Sig_/Di/jFXAOICs3QlZsnoXzE2z Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEgAyFJ+N6uu6+XupJAR8vZIA0zr0FAl2d8loACgkQAR8vZIA0 zr2WHggAttPRl8kp+yb/oZQOEp8vg1iZdn55DoxHq2LWuWy8RIoAUnOUy9TapDZ5 ZBQKgfDBYcD0Yawqlk9uOev6Uhe9roJRyVSdWjdPMcGdK0viwBagw8sYWxWD2TrY MljhCRJfoStaA/ZKClfGb2w5KddgXTgz2jqRs8CNps7aFBbjhKFtwJoKkdCjI/kl ADmw46QWkNmN6axoy3NKIDeP31lOfWpMcfcYw0MrLCn0+s/tfRpKqH9eRGC5vjJt SblR8SeFNB4oUOO1rFN9rKANzgxfqF4n06rCPORZBOK8mV5YIAA5vx7L6VOUxioj U57i4+VhXSCzlyh3HBGKN3//lb0xIA== =PTiE -----END PGP SIGNATURE----- --Sig_/Di/jFXAOICs3QlZsnoXzE2z--