From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH 11/11] spi: pxa2xx: Deal with the leftover garbage in TXFIFO Date: Sun, 4 Nov 2018 13:19:01 +0100 Message-ID: <20181104121901.GW23864@amd> References: <20181010170936.316862-1-lkundrak@v3.sk> <20181010170936.316862-12-lkundrak@v3.sk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="hc4757KF+wLS/WHK" Return-path: Content-Disposition: inline In-Reply-To: <20181010170936.316862-12-lkundrak@v3.sk> Sender: linux-kernel-owner@vger.kernel.org To: Lubomir Rintel Cc: Mark Brown , Geert Uytterhoeven , James Cameron , Rob Herring , Mark Rutland , Eric Miao , Haojian Zhuang , Daniel Mack , Robert Jarzmik , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org --hc4757KF+wLS/WHK Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed 2018-10-10 19:09:36, Lubomir Rintel wrote: > There doesn't seem to be a way to empty TXFIFO on MMP2. The datasheet is > super-secret and the method described in Armada 16x manual won't work: >=20 > "The TXFIFO and RXFIFO are cleared to 0b0 when the SSPx port is reset or > disabled (by writing a 0b0 to the field > in the SSP Control Register 0)." >=20 > # devmem 0xd4037008 # read SSSR > 0x0000F204 > # devmem 0xd4037000 32 0x80 # SSE off in SSCR0 > # devmem 0xd4037000 32 0x87 # SSE on > # devmem 0xd4037008 > 0x0000F204 > ^ TXFIFO level is still 2. Sigh. >=20 > The OLPC 1.75 boot firmware leaves two bytes in the TXFIFO. Those are > basically throwaway bytes used in response to the messages from the EC. > The OLPC kernel copes with this by power-cycling the hardware. Perhaps > the firmware should do this instead. >=20 > Other than that, there's not much we can do other than complain loudly > until the garbage gets drained and discard the actual data... For the > OLPC EC this will work just fine and pushing more data to TXFIFO would > break further transactions. >=20 > Signed-off-by: Lubomir Rintel Acked-by: Pavel Machek --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --hc4757KF+wLS/WHK Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlve47UACgkQMOfwapXb+vJ0kQCgoz2t2PBI0Wsd+Q8gcUWHfqCX G80AoJoac16+K78lqYwRylFytYLxCjR8 =13JX -----END PGP SIGNATURE----- --hc4757KF+wLS/WHK--