Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH v6 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller | From | Liang Yang <> | Date | Thu, 8 Nov 2018 15:41:53 +0800 |
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On 2018/11/7 0:16, Boris Brezillon wrote: > On Tue, 6 Nov 2018 19:08:27 +0800 > Liang Yang <liang.yang@amlogic.com> wrote: > >> On 2018/11/6 18:22, Boris Brezillon wrote: >>> On Tue, 6 Nov 2018 18:00:37 +0800 >>> Liang Yang <liang.yang@amlogic.com> wrote: >>> >>>> On 2018/11/6 17:28, Boris Brezillon wrote: >>>>> On Tue, 6 Nov 2018 17:08:00 +0800 >>>>> Liang Yang <liang.yang@amlogic.com> wrote: >>>>> >>>>>> On 2018/11/5 23:53, Boris Brezillon wrote: >>>>>>> On Fri, 2 Nov 2018 00:42:21 +0800 >>>>>>> Jianxin Pan <jianxin.pan@amlogic.com> 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. >
when using these helpers, i finally find that i still need a *info buffer* which is used to get status and ecc counter. even i don't need to check *info buffer*, it is still needed. i just malloc *info_buffer* in driver now. and then i think some dedicated dma may need a minimum size(such as 4 bytes). it is luckly that meson nfc is not limited about the minimum size and i tested it. so what is your suggestion about it?
> . >
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