From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Date: Tue, 02 Jan 2018 15:38:41 +0000 Subject: Re: [PATCH v3] backlight: tdo24m: fix the spi cs between transfers Message-Id: <20180102153841.vhzll4gcwuoemk3l@dell> List-Id: References: <20171228082742.13415-1-robert.jarzmik@free.fr> In-Reply-To: <20171228082742.13415-1-robert.jarzmik@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable To: Robert Jarzmik Cc: Daniel Thompson , Bartlomiej Zolnierkiewicz , Jingoo Han , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org On Thu, 28 Dec 2017, Robert Jarzmik wrote: > Currently the LCD display (TD035S) on the cm-x300 platform is broken and > remains blank. >=20 > The TD0245S specification requires that the chipselect is toggled > between commands sent to the panel. This was also the purpose of the > former patch of commit f64dcac0b124 ("backlight: tdo24m: ensure chip > select changes between transfers"). >=20 > Unfortunately, the "cs_change" field of a SPI transfer is > misleading. Its true meaning is that for a SPI message holding multiple > transfers, the chip select is toggled between each transfer, but for the > last transfer it remains asserted. >=20 > In this driver, all the SPI messages contain exactly one transfer, which > means that each transfer is the last of its message, and as a > consequence the chip select is never toggled. >=20 > Actually, there was a second bug hidding the first one, hence the > problem was not seen until v4.6. This problem was fixed by commit > a52db659c79c ("spi: pxa2xx: Fix cs_change management") for PXA based > boards. >=20 > This fix makes the TD035S work again on a cm-x300 board. The same > applies to other PXA boards, ie. corgi and tosa. >=20 > Fixes: a52db659c79c ("spi: pxa2xx: Fix cs_change management") Since this fixes an old kernel, I'm not going to apply it for -fixes. > Reported-by: Andrea Adami > Signed-off-by: Robert Jarzmik > Acked-by: Daniel Thompson > --- > Since v1: added 2 other panels > Since v2: added Daniel's ack > --- > drivers/video/backlight/corgi_lcd.c | 2 +- > drivers/video/backlight/tdo24m.c | 2 +- > drivers/video/backlight/tosa_lcd.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) Applied to -next, thanks. --=20 Lee Jones Linaro Services Technical Lead Linaro.org =E2=94=82 Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog