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Mon, 17 May 2021 12:24:27 +0000 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 3E0911F4202E; Mon, 17 May 2021 13:24:22 +0100 (BST) Date: Mon, 17 May 2021 14:24:18 +0200 From: Boris Brezillon To: Patrice CHOTARD Cc: Mark Brown , Miquel Raynal , Vignesh Raghavendra , , Alexandre Torgue , , , , , Subject: Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions Message-ID: <20210517142418.7689c01f@collabora.com> In-Reply-To: <21717dd0-86a7-b3d9-952e-5c7539f90bee@foss.st.com> References: <20210507131756.17028-1-patrice.chotard@foss.st.com> <20210507131756.17028-2-patrice.chotard@foss.st.com> <20210517094140.53cb643a@collabora.com> <20210517132551.7dd56a5e@collabora.com> <21717dd0-86a7-b3d9-952e-5c7539f90bee@foss.st.com> Organization: Collabora X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210517_052425_746554_112FCFF2 X-CRM114-Status: GOOD ( 36.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 17 May 2021 13:59:54 +0200 Patrice CHOTARD wrote: > Hi > > On 5/17/21 1:25 PM, Boris Brezillon wrote: > > On Mon, 17 May 2021 11:24:25 +0200 > > Patrice CHOTARD wrote: > > > >> Hi Boris > >> > >> On 5/17/21 9:41 AM, Boris Brezillon wrote: > >>> On Fri, 7 May 2021 15:17:54 +0200 > >>> wrote: > >>> > >>>> +/** > >>>> + * spi_mem_poll_status() - Poll memory device status > >>>> + * @mem: SPI memory device > >>>> + * @op: the memory operation to execute > >>>> + * @mask: status bitmask to ckeck > >>>> + * @match: (status & mask) expected value > >>>> + * @timeout_ms: timeout in milliseconds > >>>> + * > >>>> + * This function send a polling status request to the controller driver > >>>> + * > >>>> + * Return: 0 in case of success, -ETIMEDOUT in case of error, > >>>> + * -EOPNOTSUPP if not supported. > >>>> + */ > >>>> +int spi_mem_poll_status(struct spi_mem *mem, > >>>> + const struct spi_mem_op *op, > >>>> + u16 mask, u16 match, u16 timeout_ms) > >>> > >>> Maybe you should pass a delay_us too, to poll the status at the right > >>> rate in the SW-based case (can also be used by drivers if they need to > >> > >> Ok, i will add a polling_rate_us parameter to poll_status() callback, > >> even if in STM32 driver case we will not use it, i agree it should be useful > >> depending of driver's implementation. > >> > >>> configure the polling rate). You could also add an initial_delay_us to > >>> avoid polling the status too early: an erase operation will take longer > >>> than a write which will take longer than a read. No need to check the > >>> status just after issuing the command, especially if the polling is > >>> done in SW. Those 2 arguments should also be passed to the driver. > >> > >> Regarding the addition of an initial_delay_us. We got two solution: > >> - use the same polling rate already used by read_poll_timeout() and > >> set read_poll_timeout()'s sleep_before_read parameter to true (in our case 20 us > >> will be used as initial delay and as polling rate). > >> > >> - add an udelay(initial_delay_us) or even better usleep_range(initial_delay_us, > >> initial_delay_us + delta) before calling read_poll_timeout(). > >> > >> I imagine you prefer the second solution ? > > > > Yep, you might want to use udelay() when the delay is small and > > usleep_range() otherwise. > > > >> > >> By adding polling_rate_us and initial_delay_us parameters to > >> spi_mem_poll_status(), it implies to update all spinand_wait() calls for > >> different operations (reset, read page, write page, erase) with respective > >> initial_delay_us/polling_rate_us values for spi_mem_poll_status()'s parameters. > >> > >> Can you provide adequate initial_delay_us and polling rate_us for each operation type ?. > > > > If I refer to the datasheets I have, > > > > tBERS (erase) 1ms to 4ms > > tPROG 300us to 400us > > tREAD 25us to 100us > > > > Let's assume we want to minimize the latency, I'd recommend dividing > > the min value by 4 for the initial delay, and dividing it by 20 for the > > poll delay, which gives: > > > > ERASE -> initial_delay = 250us, poll_delay = 50us > > PROG -> initial_delay = 100us, poll_delay = 20us > > READ -> initial_delay = 6us, poll_delay = 5us > > > What about RESET ? we also need an initial and poll delay too (see spinand_reset_op() ) 5us/10us/500us if the device is respectively reading/programming/erasing when the RESET occurs. Since we always issue a RESET when the device is IDLE, I'd recommend going for 5us for both the initial_delay and poll_delay. > > > > > Of course, that'd be even better if we were able to extract this > > information from the NAND ID (or ONFI table), but I guess we can live > > with those optimistic values in the meantime. > > > > Thanks > Patrice _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel