From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 6 Nov 2018 17:16:55 +0100 From: Boris Brezillon To: Liang Yang Cc: Jianxin Pan , , Yixun Lan , David Woodhouse , Brian Norris , Marek Vasut , Richard Weinberger , Jerome Brunet , Neil Armstrong , Martin Blumenstingl , Carlo Caione , Kevin Hilman , Rob Herring , Jian Hu , Hanjie Lin , Victor Wan , , , Subject: Re: [PATCH v6 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller Message-ID: <20181106171655.3808d8eb@bbrezillon> In-Reply-To: <99475361-0115-7c16-3b7e-8f0d3a779446@amlogic.com> References: <1541090542-19618-1-git-send-email-jianxin.pan@amlogic.com> <1541090542-19618-3-git-send-email-jianxin.pan@amlogic.com> <20181105165321.7ea2b45f@bbrezillon> <20181106102851.61deb97a@bbrezillon> <20181106112206.65a70a81@bbrezillon> <99475361-0115-7c16-3b7e-8f0d3a779446@amlogic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 6 Nov 2018 19:08:27 +0800 Liang Yang wrote: > On 2018/11/6 18:22, Boris Brezillon wrote: > > On Tue, 6 Nov 2018 18:00:37 +0800 > > Liang Yang wrote: > > > >> On 2018/11/6 17:28, Boris Brezillon wrote: > >>> On Tue, 6 Nov 2018 17:08:00 +0800 > >>> Liang Yang wrote: > >>> > >>>> On 2018/11/5 23:53, Boris Brezillon wrote: > >>>>> On Fri, 2 Nov 2018 00:42:21 +0800 > >>>>> Jianxin Pan wrote: > >>>>> > >>>>>> + > >>>>>> +static inline u8 meson_nfc_read_byte(struct mtd_info *mtd) > >>>>>> +{ > >>>>>> + struct nand_chip *nand = mtd_to_nand(mtd); > >>>>>> + struct meson_nfc *nfc = nand_get_controller_data(nand); > >>>>>> + u32 cmd; > >>>>>> + > >>>>>> + cmd = nfc->param.chip_select | NFC_CMD_DRD | 0; > >>>>>> + writel(cmd, nfc->reg_base + NFC_REG_CMD); > >>>>>> + > >>>>>> + meson_nfc_drain_cmd(nfc); > >>>>> > >>>>> You probably don't want to drain the FIFO every time you read a byte on > >>>>> the bus, and I guess the INPUT FIFO is at least as big as the CMD > >>>>> FIFO, right? If that's the case, you should queue as much DRD cmd as > >>>>> possible and only sync when the user explicitly requests it or when > >>>>> the INPUT/READ FIFO is full. > >>>>> > >>>> Register 'NFC_REG_BUF' can holds only 4 bytes, also DRD sends only one > >>>> nand cycle to read one byte and covers the 1st byte every time reading. > >>>> i think nfc controller is faster than nand cycle, but really it is not > >>>> high efficiency when reading so many bytes once. > >>>> Or use dma command here like read_page and read_page_raw. > >>> > >>> Yep, that's also an alternative, though you'll have to make sure the > >>> buffer passed through the nand_op_inst is DMA-safe, and use a bounce > >>> buffer when that's not the case. > >>> > >> ok, i will try dma here. > > > > We should probably expose the bounce buf handling as generic helpers at > > the rawnand level: > > > > void *nand_op_get_dma_safe_input_buf(struct nand_op_instr *instr) > > { > > void *buf; > > > > if (WARN_ON(instr->type != NAND_OP_DATA_IN_INSTR)) > > return NULL; > > > > if (virt_addr_valid(instr->data.in) && > > !object_is_on_stack(instr->data.buf.in)) > > return instr->data.buf.in; > > > > return kzalloc(instr->data.len, GFP_KERNEL); > > } > > > > void nand_op_put_dma_safe_input_buf(struct nand_op_instr *instr, > > void *buf) > > { > > if (WARN_ON(instr->type != NAND_OP_DATA_IN_INSTR) || > > WARN_ON(!buf)) > > return; > > > > if (buf == instr->data.buf.in) > > return; > > > > memcpy(instr->data.buf.in, buf, instr->data.len); > > kfree(buf); > > } > > > > const void *nand_op_get_dma_safe_output_buf(struct nand_op_instr *instr) > > { > > void *buf; > > > > if (WARN_ON(instr->type != NAND_OP_DATA_OUT_INSTR)) > > return NULL; > > > > if (virt_addr_valid(instr->data.out) && > > !object_is_on_stack(instr->data.buf.out)) > > return instr->data.buf.out; > > > > return kmemdup(instr->data.buf.out, GFP_KERNEL); > > } > > > > void nand_op_put_dma_safe_output_buf(struct nand_op_instr *instr, > > void *buf) > > { > > if (WARN_ON(instr->type != NAND_OP_DATA_OUT_INSTR) || > > WARN_ON(!buf)) > > return; > > > > if (buf != instr->data.buf.out) > > kfree(buf); > > } > > > > that is more convenient. > i will use meson_chip->databuf as the bounce mid-buffer now. It won't work: the bounce buffer is allocated after the detection, and the detection code is calling ->exec_op(). Just add a new patch to you series adding these helpers to nand_base.c.