From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758225AbcGKKYA (ORCPT ); Mon, 11 Jul 2016 06:24:00 -0400 Received: from bear.ext.ti.com ([198.47.19.11]:59287 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751847AbcGKKX7 (ORCPT ); Mon, 11 Jul 2016 06:23:59 -0400 Subject: Re: [PATCH] spi: spi-ti-qspi: clear wlen field while setting word length. To: prahlad venkata References: <1468094753-8327-1-git-send-email-prahlad.eee@gmail.com> <5783297C.7080702@ti.com> <57835C62.7030704@ti.com> <57836395.3030602@ti.com> CC: "broonie@kernel.org" , "linux-spi@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: Vignesh R Message-ID: <578373AE.5060803@ti.com> Date: Mon, 11 Jul 2016 15:53:42 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 11 July 2016 02:49 PM, prahlad venkata wrote: > On Mon, Jul 11, 2016 at 2:45 PM, Vignesh R wrote: [...] >>>>>>>> diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c >>>>>>>> index 29ea8d2..6c61f54 100644 >>>>>>>> --- a/drivers/spi/spi-ti-qspi.c >>>>>>>> +++ b/drivers/spi/spi-ti-qspi.c >>>>>>>> @@ -276,9 +276,9 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t, >>>>>>>> cmd |= QSPI_WLEN(QSPI_WLEN_MAX_BITS); >>>>>>>> } else { >>>>>>>> writeb(*txbuf, qspi->base + QSPI_SPI_DATA_REG); >>>>>>>> - cmd = qspi->cmd | QSPI_WR_SNGL; >>>>> >>>>> This is wrong. Deleting this line means QSPI_WR_SNGL is not set and no >>>>> data is sent out on the wire. >>>> QSPI_WR_SNGL is already set as soon as we enter the function. >>>>> >>>>>>> >>>>>>> qspi->cmd always has WLEN field cleared and set to WLEN = 1 byte (see >>>>>>> ti_qspi_start_transfer_one()). And hence variable 'cmd' will also have >>>>>>> WLEN set to 1 byte. >>>>>> Even though WLEN=1 is set in the ti_qspi_transfer_one, if we ask for a >>>>>> transfer of large data, >>>>>> say 300 bytes in length, for attaining faster data rate WLEN 128 is >>>>>> selected for the first two >>>>>> transactions and remaining 44 bytes will be transmitted with WLEN 1. >>>>>> During that case, >>>>>> WLEN will be changed inside qspi_write_msg function itself and the >>>>>> field should be cleared >>>>>> first while doing that. >>>>> >>>>> In qspi_write_msg(), qspi->cmd will always have WLEN set to >>>>> QSPI_WLEN(t->bits_per_word) and qspi->cmd is never changed within this >>>>> function. >>>>> It is the value of local variable 'cmd' that is changed to appropriate >>>>> WLEN (128bit or 8bit) as necessary. >> >>> 'cmd' is written back to qspi->cmd for every transaction. >> >> You mean qspi->cmd = cmd ? >> I don't see this happening anywhere in the driver. Can you point me to >> that line of code? > line 296: > ti_qspi_write(qspi, cmd, QSPI_SPI_CMD_REG); Sorry, I don't understand. QSPI_SPI_CMD_REG and qspi->cmd are different. qspi->cmd does not represent the QSPI_SPI_CMD_REG register. qspi->cmd is just local driver data for book-keeping. Please add some prints in driver to see how 'cmd' (and qspi->cmd) variable changes in case of 128bit mode and 8bit mode. Regards Vignesh -- Regards Vignesh