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[108.51.35.162]) by smtp.googlemail.com with ESMTPSA id k15sm2513306qtk.64.2020.11.07.05.30.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Nov 2020 05:30:22 -0800 (PST) Subject: Re: [PATCH 03/32] spi: dw: Fix driving MOSI low while recieving To: Damien Le Moal , Palmer Dabbelt , linux-riscv@lists.infradead.org, Rob Herring , Frank Rowand , devicetree@vger.kernel.org, Serge Semin , Mark Brown , linux-spi@vger.kernel.org, Stephen Boyd , linux-clk@vger.kernel.org, Linus Walleij , linux-gpio@vger.kernel.org, Philipp Zabel References: <20201107081420.60325-1-damien.lemoal@wdc.com> <20201107081420.60325-4-damien.lemoal@wdc.com> From: Sean Anderson Autocrypt: addr=seanga2@gmail.com; prefer-encrypt=mutual; keydata= mQENBFe74PkBCACoLC5Zq2gwrDcCkr+EPGsT14bsxrW07GiYzQhLCgwnPdEpgU95pXltbFhw 46GfyffABWxHKO2x+3L1S6ZxC5AiKbYXo7lpnTBYjamPWYouz+VJEVjUx9aaSEByBah5kX6a lKFZWNbXLAJh+dE1HFaMi3TQXXaInaREc+aO1F7fCa2zNE75ja+6ah8L4TPRFZ2HKQzve0/Y GXtoRw97qmnm3U36vKWT/m2AiLF619F4T1mHvlfjyd9hrVwjH5h/2rFyroXVXBZHGA9Aj8eN F2si35dWSZlIwXkNu9bXp0/pIu6FD0bI+BEkD5S7aH1G1iAcMFi5Qq2RNa041DfQSDDHABEB AAG0K1NlYW4gR2FsbGFnaGVyIEFuZGVyc29uIDxzZWFuZ2EyQGdtYWlsLmNvbT6JAVcEEwEK AEECGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4ACGQEWIQSQYR1bzo1I0gPoYCg+6I/stKEQ bgUCXT+S2AUJB2TlXwAKCRA+6I/stKEQbhNOB/9ooea0hU9Sgh7PBloU6CgaC5mlqPLB7NTp +JkB+nh3Fqhk+qLZwzEynnuDLl6ESpVHIc0Ym1lyF4gT3DsrlGT1h0Gzw7vUwd1+ZfN0CuIx Rn861U/dAUjvbtN5kMBqOI4/5ea+0r7MACcIVnKF/wMXBD8eypHsorT2sJTzwZ6DRCNP70C5 N1ahpqqNmXe0uLdP0pu55JCqhrGw2SinkRMdWyhSxT56uNwIVHGhLTqH7Q4t1N6G1EH626qa SvIJsWlNpll6Y3AYLDw2/Spw/hqieS2PQ/Ky3rPZnvJt7/aSNYsKoFGX0yjkH67Uq8Lx0k1L w8jpXnbEPQN3A2ZJCbeM Message-ID: <2f2acc07-aa00-5d21-e8f6-d99407bf9590@gmail.com> Date: Sat, 7 Nov 2020 08:30:21 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201107081420.60325-4-damien.lemoal@wdc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 11/7/20 3:13 AM, Damien Le Moal wrote: > Fix for the Synopsis DesignWare SPI mmio driver taken from the work > by Sean Anderson for the U-Boot project. Sean comments: > > The resting state of MOSI is high when nothing is driving it. If we > drive it low while recieving, it looks like we are transmitting 0x00 > instead of transmitting nothing. This can confuse slaves (like SD cards) > which allow new commands to be sent over MOSI while they are returning > data over MISO. The return of MOSI from 0 to 1 at the end of recieving > a byte can look like a start bit and a transmission bit to an SD card. > This will cause the card to become out-of-sync with the SPI device, as > it thinks the device has already started transmitting two bytes of a new > command. The mmc-spi driver will not detect the R1 response from the SD > card, since it is sent too early, and offset by two bits. This patch > fixes transfer errors when using SD cards with dw spi. > > Signed-off-by: Sean Anderson > Signed-off-by: Damien Le Moal > --- > drivers/spi/spi-dw-core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c > index 841c85247f01..c2ef1d8d46d5 100644 > --- a/drivers/spi/spi-dw-core.c > +++ b/drivers/spi/spi-dw-core.c > @@ -137,7 +137,7 @@ static inline u32 rx_max(struct dw_spi *dws) > static void dw_writer(struct dw_spi *dws) > { > u32 max = tx_max(dws); > - u16 txw = 0; > + u16 txw = 0xffff; > > while (max--) { > if (dws->tx) { > Reviewed-by: Sean Anderson